Title : Novel Transition Metal Substituted Polyoxometalates and Process For Their Preparation

Inventors Ulrich Kortz Sib Sankar MaI

Statement of Related Cases

[0001] This application relates to USSN 11/445,073, filed May 31, 2006, USSN 11/443,683, filed May 31, 2006, and USSN 11/445,095, filed May 31, 2006.

Field of the Invention

[0002] This invention relates to new copper-, zinc-, palladium- and/or platinum-substituted polyoxymetalates, a process for their preparation, and their use for the catalytic oxidation of organic molecules.

Background of the Invention

[0003] Polyoxometalates (POMs) are a unique class of inorganic metal-oxygen clusters. They consist of a polyhedral cage structure or framework bearing a negative charge, which is balanced by cations that are external to the cage, and may also contain centrally located heteroatom (s) surrounded by the cage framework. Generally, suitable heteroatoms include Group Ilia to Via elements such as phosphorus, antimony, silicon and boron. The framework of polyoxometalates typically comprises a plurality of metal atoms (addenda) , which can be the same or different, bonded to oxygen atoms. Due to appropriate cation radius and good π-electron acceptor properties, the framework metal is generally limited to a few elements such as tungsten, molybdenum, vanadium, niobium and tantalum.

[0004] In the past, there have been increasing efforts towards the modification of polyoxoanions with various organic and/or transition metal complex moieties with the aim of generating new catalyst systems as well as functional materials with in-

teresting optical, electronic and magnetic properties. In particular, transition metal substituted polyoxometalates

(TMSPs) have attracted continuously growing attention as they can be rationally modified on the molecular level including size, shape, charge density, acidity, redox states, stability, solubility, etc.

[0005] For example, Kortz et al . report on the palladium (II) - substituted, dimeric, lone pair containing polyanion [Cs ₂ Na(H ₂ O) ₁₀ Pd ₃ ((X-SbW ₉ O ₃₃ ) 2] ^9" (Inorg. Chem. 2004, 43, 3915- 3920). This polyanion was synthesized by reacting Pd(CH ₃ COO) ₂ with [Gi-SbW ₉ O ₃₃ ] ^9~ in aqueous acidic medium. The square-planar palladium (II) ions are located in the central belt of the sandwich-type structure connecting two (01-SbW ₉ O ₃₃ ) Keggin moieties via bonding to oxygen atoms of the WOβ octahedra. The central belt of this polyoxometalate is completed by two Cs ⁺ - ions and one Na ⁺ -ion which occupy the vacancies between the palladium centers. [0006] Moreover, Kortz et al . report on the palladium (II) - substituted, lone pair containing polyanion [Cs ₂ Na (H ₂ O) sPd ₃ (α- AsW ₉ O ₃₃ ) ₂ ] ^9" (Eur. J. Inorg. Chem. 2005, 3034-3041). This polyanion was synthesized by reacting PdCl ₂ with [0,-AsW ₉ O ₃₃ ] ^9~ in aqueous acidic medium and can be considered as the As-analogue of the above mentioned [Cs ₂ Na (H ₂ O) 10Pd ₃ (0,-SbW ₉ O ₃₃ ) ₂ ] ^9~ . [0007] Further, Kortz et al . disclose the synthesis of the dimeric polyanions [ (01-XW ₉ O ₃₃ ) ₂ M ₃ (H ₂ O) ₃ ] ^12~ (M = Cu ²⁺ , Zn ²⁺ ; X = As ¹¹¹ , Sb ¹¹¹ ) (Inorg. Chem. 2001, 40, 4742-4749) . Like the above palladium substituted POMs, also these polyanions belong to the class of Herve-type sandwich POMs, i.e. they comprise two [0,-XW ₉ O ₃₃ ] units. The α-Keggin fragments of these polyanions are joined by three equivalent Cu ²⁺ or Zn ²⁺ ions each having one terminal water molecule resulting in square pyramidal coordination geometry. The addenda positions between the three

transition metal ions are occupied by three sodium ions leading to a central belt of six metal atoms altering in position. [0008] In addition, Kortz et al . , Inorg. Chem. 2004, 43, 144-

154, describe the preparation of (K ₇ Na [Cu ₄ K ₂ (H ₂ O) β (α- ASW9O33) 2] ' 5.5H ₂ O} . This polyanion consists of two (OI-XW9O33) units joined by a cyclic arrangement of four Cu ²⁺ and two K ⁺ ions, i.e. the central belt is composed of three adjacent, edge-shared CuO ₄ (H ₂ O) square pyramides and a unique CuO ₄ (H ₂ O) fragment which is separated from the copper triad by two po- tassium ions.

[0009] Furthermore, Yamase et al . describe the synthesis of [ (CuCl) 6 (ASW9O33) 2] ^12~ by replacement of a di-lanthanide moiety in [ (Eu (H ₂ O) } ₂ (ASW9O33) 2] ^12~ with a Cu ₆ hexagon (Inorg. Chem. 2006, 45, 7698-7704) . The hexagon composed of penta- coordinated transition-metal-ions is found to be sandwiched by two [B-«-AsW ₉ θ33] ^9~ ligands. [0010] Additional references of interest include:

1. Observation of a Half Step Magnetization in the (Cu ₃ }-Type Triangular Spin Ring, Choi, K. -Y.; Matsuda, Y. H.; Nojiri, H.; Kortz, U.; Hussain, F.; Stowe, A. C; Ramsey, C; Dalai N. S. Phys. Rev. Lett. 2006, 96, 107202.

2. The Wheel-Shaped Cu20-Tungstophosphate

[Cu ₂₀ Cl (OH) ₂₄ (H ₂ O) _I2 (P ₈ W ₄₈ Oi ₈₄ ) ] ^25" Ion, MaI, S. S.; Kortz, U. Angew. Chem. Int. Ed. 2005, 44, 3777-3780. 3. Synthesis and Structure of the Penta-Copper (II) Substituted Tungstosilicate [Cu ₅ (OH) ₄ (H ₂ O) ₂ (A-α-SiW ₉ O ₃₃ ) 2] ^10" ,Bi, L . - H.; Kortz, U. Inorg. Chem. 2004, 43, 7961-7962.

4. Magnetic Properties of Lone Pair Containing, Sandwich-Type Polyoxoanions : A Detailed Study of the Heteroatom Effect Stowe, A. C; Nellutla, S.; Dalai, N. S.; Kortz, U. Eur. J. Inorg. Chem. 2004, 3792-3797.

5. Sandwich-type Germanotungstates : Structure and Magnetic Properties of the Dimeric Polyoxoanions [M ₄ (H ₂ O) ₂ (GeW ₉ O ₃₄ ) ₂ ] ^12~

(M = Mn ²⁺ , Cu ²⁺ , Zn ²⁺ , Cd ²⁺ ) . Kortz , U . ; Ne l lut l a , S . ; S towe , A .

C; Dalai, N. S.; Rauwald, U.; Danquah, W.; Ravot, D. Inorg.

Chem. 2004, 43, 2308-2317.

6. Sandwich-Type Silicotungstates : Structure and Magnetic Properties of the Dimeric Polyoxoanions [{ SiM ₂ W ₉ Os ₄ (H ₂ O) } ₂ ] ^12~ (M

= Mn ²⁺ , Cu ²⁺ , Zn ²⁺ ). Kortz, U.; Isber, S.; Dickman, M. H.;

Ravot, D. Inorg. Chem. 2000, 39, 2915-2922.

[0011] However, up to now the known transition metal substituted polyanions have not turned out to be very useful for ho- mogeneous or heterogeneous catalytic applications.

[0012] Therefore, it is an object of the present invention to provide transition metal substituted polyoxometalates which are useful as catalysts in homogeneous and heterogeneous oxidation reactions of organic substrates. Furthermore, such transition metal substituted POMs should be easy and reproducible to prepare.

[0013] These objects are achieved by polyoxometalates described herein.

Summary of the Invention

[0014] This invention relates to polyoxometalates represented by the formula I :

(A _n ) ^m+ [M _γ (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^m" (I) or solvates thereof, wherein

A represents a cation, n is the number of the cations A, m is the charge of the polyoxoanion,

M represents a transition metal (s) selected from Cu,

Zn, Pd, Pt and mixtures thereof, y is the number of transition metals M and is a number greater than 4 and less than 6,

p is the number of water molecules and is a number from 0 to 10,

X is a halide selected from the group consisting of F,

Cl, Br, I and mixtures thereof, z is the number of halides and is a number from 0 to 6, and

Z represents a heteroatom selected from the group consisting of Sb ¹¹¹ , Bi ¹¹¹ , As ¹¹¹ , Se ^IV and Te ^Iv .

Brief Description of the Figures

[0015] Figure 1 is an illustration of the structure of a given polyanion according to the invention having 5 Cu(II) and one vacancy in the central belt.

Detailed Description of the Invention

[0016] The CAS numbering scheme for the Periodic Table Groups is used as published in CHEMICAL AND ENGINEERING NEWS, 63 (5) , 27

(1985) .

[0017] This invention relates to polyoxometalates represented by the formula I:

(A _n ) ^m+ [M _γ (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^m" (I) or solvates thereof, wherein

A represents a cation, n is the number of the cations A, m is the charge of the polyoxoanion,

M represents a transition metal selected from Cu, Zn, Pd, Pt and mixtures thereof, preferably Cu y is the number of transition metals M and is a number greater than 4 and less than 6, p is the number of water molecules and is a number from 0 to 10,

X is a halide selected from the group consisting of F, Cl, Br, I and mixtures thereof, preferably Cl, z is the number of halides and is a number from 0 to 6, and Z is a heteroatom selected from Sb ¹¹¹ , Bi ¹¹¹ , As ¹¹¹ , Se ^IV and Te ^Iv .

[0018] In some embodiments of POM molecules of the polyoxome- talates according to the invention, the number y of transition metals M is 5. However, in alternate embodiments, based on all POM molecules of a given sample, the value of y is an average of the molecules in the sample and is greater than 4 and less than 6. For example, in the formulae above, the value of y can be 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8 or 5.9, with the value for y corresponding to mixtures of polyoxometalates typically having four or five or six transition metal centers. Mixtures of a polyoxometalate of formula I or a solvate thereof having five transition metals with polyoxometalates of formula I or solvates thereof having four transition metals are particularly preferred so that the value of y is preferably greater than 4 and less than 5. More preferably, the value of y is about 4.3, 4.4 or 4.5. Most preferably, the average value of y is about 4.5. According to another embodiment of the inven- tion, substantially all polyoxometalate molecules of a given sample have 5 transition metal centers. For this embodiment not only is the value of y equal to 5 for a given sample, but also for each POM molecule the individual value of y is 5. By substantially all is meant that y is 5 in at least 95 % of the POM molecules in a given sample.

[0019] This invention also relates to heterogeneous or homogeneous polyoxometalate compositions represented by the formula I (above) and a process to make heterogeneous or homogeneous polyoxometalate compositions represented by formula II (be-

low) , as well as process to use these polyoxometalates to polymerize olefins. For purposes of this invention and the claims thereto a heterogeneous polyoxometalate composition is a mixture of polyoxometalates having different numbers (i.e. 4, 5 or 6) of transition metal centers, and a homogeneous polyoxometallate composition is a mixture of polyoxometalates having the same number of transition metal centers. Typically, in formulae I and II y is a number greater than 4 and less than 6 when the composition is heterogeneous and is 5 when the composition is homogeneous; however, one should also note that a heterogeneous POM composition can have a y of 5. [0020] One of ordinary skill in the art will recognize that the formulae described above may represent a single species of POM molecule or a given sample containing multiple different POM molecules and as such the values for m, n, y, p, and z may or may not be whole numbers. When y is a whole number, it is clear to one of ordinary skill in the art that y represents a single type of POM molecule. When y is not a whole number, it is clear to one of ordinary skill in the art that y represents an average of all polyoxometalate molecules of a given sample. In addition when the phrase "is a number from" is used it is meant to encompass and disclose all numbers between the two values to one digit past the decimal point. For example the phrase "is a number from 0 to 1" discloses 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0.

[0021] In a preferred embodiment, the transition metal M is Cu. In another preferred embodiment, the halide X is Cl. In yet another preferred embodiment, the halide X is Cl and the transition metal M is Cu. [0022] The polyanion [M _y (H ₂ O) _P X _Z Z ₂ W ₁₈ O ₆₆ ] ^m" of the polyoxometalates described above has been found to exist in a Herve-type structure, i.e. it is a dimeric POM comprising two trilacunary Keggin fragments α- [ZW9O33] ^p~ (where Z is a heteroatom selected from Sb ¹¹¹ , Bi ¹¹¹ , As ¹¹¹ , Se ^IV and Te ^Iv .) which are connected by a

central belt consisting of six addenda positions. These six addenda positions are occupied by transition metals M. In accordance with the definition of y, on average more than 4 but less than 6 addenda positions are occupied by M. Since not all six addenda positions are occupied by M, vacancies in the central belt result. Optionally, these vacancies can be occupied by cations A. In the case where the transition metal M is Cu and/or Zn, each M has one terminal water ligand resulting in a central belt comprising MO4 (H2O) square pyramids. In the case where the transition metal M is Pd(II) or Pt(II), it is coordinated in a square-planar fashion, i.e. no terminal water ligands are bound to M. As an illustration, the structure of a preferred polyanion having 5 Cu(II) and one vacancy in the central belt is depicted in Figure 1. Each Cu(II) is ligated with one terminal water molecule or one terminal hal- ide such as chloride.

[0023] As water and halide ligands can be substituted easily, the polyoxometalates of the invention allow an easy generation of free coordination sites at the catalytically active transi- tion metal M. Consequently, the metal centers are readily accessible for other ligands including organic substrates and oxygen donor species such as O ₂ , H ₂ O ₂ , organic peroxides (e.g. t- (C ₄ H ₉ )OOH) or peracids (e.g. CH ₃ COOOH) which in turn improve the catalytic performance in oxidation reactions. In addi- tion, the presence of vacancies in the central belt of the present POMs even enhances this accessibility.

[0024] The cation A (in Formula I above) is typically a Group Ia, Ha, IHb, IVb, Vb, VIb, VIIb, VIIIb, Ib, Hb, IHa, IVa, Va and Via metal or an organic cation. In a preferred embodi- ment, A is selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, titanium, vanadium, chromium, lanthanum, lantha- nide metal, actinide metal, manganese, iron, cobalt, nickel, copper, zinc, ruthenium, palladium, platinum, tin, antimony,

tellurium, phosphonium such as tetraalkylphosphonium, ammonium, guanidinium, tetraalkylammonium, protonated aliphatic amines, protonated aromatic amines or combinations thereof. More preferably, A is selected from sodium, potassium, ammo- nium and combinations thereof. Generally, A acts as counterion of the polyanion and is therefore positioned outside of the POM framework. However, it is also possible that one or more cations A can occupy a vacancy of the central belt and thus take a position within the framework of the polyanion. [0025] The number n of cations is dependent on the nature of cation (s) A, namely its/their valence, and the negative charge m of the polyanion which has to be balanced. In any case, the overall charge of all cations A is equal to the charge of the polyanion. In turn, the charge m of the polyanion is depend- ent on the oxidation state and the number of the transition metals M, the oxidation state of the heteroatom Z, the oxidation state of transition metal M as well as the number of hal- ides z. In some embodiments m is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 for a given POM molecule. Preferably m is a number from 1 to 12. Accordingly, based on all POM molecules of a given sample values of m of more than 1 and less than 12 such as 9.5 or 10 can be obtained. In some embodiments, n is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 for a given POM molecule. Accordingly, the value of n for a given sample can be more than 1 and less than 12, e.g. 9.5 or 10. Preferably n is a number from 1 to 12.

[0026] The oxidation state of M comprised in the present poly- oxometalates can range from (I) to (IV) and preferably is (II) . In a preferred embodiment the transition metal M is copper, preferably copper (II) . It is also possible that in a given POM molecule M is a mixture of Cu, Zn, Pd and/or Pt, i.e. that the six addenda positions in the central belt are occupied by different transition metals, for example 1 Pd and 4 Cu, 2 Pd and 3 Cu, 3 Pd and 2 Cu, etc.

[0027] The water molecules which can be present in polyoxome- talates according to the invention are bound to M and optionally to one or more cations A occupying an addenda position of the framework. The number p of water molecules bound to M and/or A depends on the number and nature of transition metal M and is 1 for each Cu and Zn center incorporated in the central belt, but is 0 for each palladium and platinum center. Moreover, p depends on the number and nature of cations A occupying an addenda position. For example, each potassium ion will usually bear two water ligands. Finally, p depends on the number z of halides such as chloride ions since halides are ligated to Cu and/or Zn centers instead of water. In a preferred embodiment, p is a number from 0 to 10 and can for example be 3, 4 or 5. [0028] The halides X which can be present in the polyoxometa- lates according to the invention are bound to M or optionally, especially in the solid state, to a cation A located in the central belt of the POM. Typically, the halides X are bound to M. In a further preferred embodiment, chloride is used as halide X.

[0029] The number z of halides is a number from 0 to 6 and for example is 0, 1 or 2. Generally, the presence of halides such as chloride ligands instead of water ligands bound to the transition metal centers M increases the negative charge of the polyanion. In some embodiments, the negative charge of the polyanion might become too low and thus the polyanion might become too unstable if the number y of transition metals increases. Hence, in a preferred embodiment, the number z of halides increases with the number of transition metals incor- porated into the central belt of the polyanion.

[0030] The heteroatom Z of the polyoxometalates according to the invention is advantageously selected from As, Sb and Bi and is preferably Sb.

[0031] Accordingly, suitable examples of polyoxometalates according to the invention are represented by the formulae:

(A _n ) ^m+ [Cu ₅ (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^m" , e.g.

(A _n ) ^m+ [Cu ₅ (H ₂ O) _p X _z As ₂ W ₁₈ O ₆₆ ] ^m~ , such as

(A _n ) ^m+ [Cu ₅ (H ₂ O) _P Cl ₂ As ₂ W ₁₈ O ₆₆ ] ¹ " ^" , e.g.

(A _n ) ^m+ [Cu ₅ (H ₂ O) ₄ ClAs ₂ W ₁₈ O ₆₆ ]" ^" ,

(A _n ) ^m+ [Cu ₅ (H ₂ O) _p X _z Sb ₂ W ₁₈ O ₆₆ ] ^m" , such as

(A _n ) ^m+ [Cu ₅ (H ₂ O) _p Cl _z Sb ₂ W ₁₈ O ₆₆ ] ^m" , e.g.

(A _n ) ^m+ [Cu ₅ (H ₂ O) ₄ ClSb ₂ W ₁₈ O ₆₆ ] ¹ " ^" ,

(A _n ) ^m+ [Cu ₅ (H ₂ O) _p X _z Bi ₂ W ₁₈ O ₆₆ ] ^m" , such as

(A _n ) ^m+ [Cu ₅ (H ₂ O) _p Cl _z Bi ₂ W ₁₈ O ₆₆ ] ^m" , e.g.

(A _n ) ^m+ [Cu ₅ (H ₂ O) ₄ ClBi ₂ W ₁₈ O ₆₆ ]" ^" ,

(A _n ) ^m+ [Cu _4-5 (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^m" , e.g.

(A _n T ⁺ [Cu _4-5 (H ₂ O) ₄ CIo _-5 X ₂ W ₁₈ O ₆₆ ] ¹ " ^" , such as

(A _n ) ^{9^5+} [Cu _4-5 (H ₂ O) ₄ CIo _-5 As ₂ W ₁₈ O ₆₆ ] ⁹ - ^5" and

(A _n ) ^{9^5+} [Cu _4-5 (H ₂ O) ₄ Cl _0-5 Sb ₂ W ₁₈ O ₆₆ ] ⁹ - ^5" , or

(A _n T ⁺ [Cu _4-5 (H ₂ O) _3-5 ClZ ₂ W ₁₈ O ₆₆ ] ¹ " ^" , such as

(A _n ) ¹⁰⁺ [Cu _4-5 (H ₂ O) ₃ . ₅ ClBi ₂ W ₁₈ O ₆₆ ] ^10" ,

(A _n ) ^m+ [PdCu ₄ L ₄ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^" ,

(A _n T m+ ⁺ [Pd ₂ Cu ₃ L ₃ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^" ,

(A _n ) ^m+ [Pd ₃ Cu ₂ L ₂ Z ₂ W ₁₈ O ₆₆ ;

(A _n ) ^m+ [PtCu ₄ L ₄ Z ₂ W ₁₈ O ₆₆ ]" ^" ,

(A _n ) ^m+ [Pt ₂ Cu ₃ L ₃ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^" ,

(A _n ) ^m+ [Pt ₃ Cu ₂ L ₂ Z ₂ W ₁₈ O ₆₆ ]" ^" ,

(A _n ) ^m+ [PdZn ₄ L ₄ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^" ,

(A _n ) ^m+ [Pd ₂ Zn ₃ L ₃ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^" ,

(A _n ) ^m+ [Pd ₃ Zn ₂ L ₂ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^" ,

(A _n ) ^m+ [PtZn ₄ L ₄ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^" ,

(A _n ) ^m+ [Pt ₂ Zn ₃ L ₃ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^" , and

(A _n ) ^m+ [Pt ₃ Zn ₂ L ₂ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^" , wherein L is a ligand bound to the transition metal M selected from H ₂ O or X (where X is a halide selected from the group consisting of F, Cl, Br, I and mixtures thereof, preferably Cl) , and wherein A, n, m, p, z, and Z are as described above. [0032] The invention also includes solvates of the POMs de- scribed herein. A solvate is an association of solvent molecules with a polyoxometalate . Preferably, water is associated with the POMs and thus, POMs useful herein can be represented by the formula

(A _n ) ^m+ [M _y (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^{m" •} xH ₂ 0, such as

(A _n ) ^m+ [CU _y (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^{m" •} XH ₂ O, wherein x represents the number of hydrate water molecules per POM molecule, exclusive of the water molecules which are bound as ligands to M or optionally A positioned in the framework, and mostly depends on the type of cations A (and wherein A, n, m, M, y, p, X, z, Z, are as described above) . In some embodi-

ments x is an integer from 1 to 50 such as 2, 4, 5, 6, 8, 10, 11, 12, 16, 18, 20, 22, 24, 25, 26, or 30.

[0033] Suitable examples of polyoxometalate solvates according to the invention are represented by the formulae:

(A _n ) ^m+ [Cu ₅ (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^{m" •} XH ₂ O, e.g.

(A _n ) ^m+ [Cu ₅ (H ₂ O) _p X _z As ₂ W ₁₈ O ₆₆ ] ^{m" •} XH ₂ O, such as

(A _n ) ^m+ [Cu ₅ (H ₂ O) _p Cl _z As ₂ W ₁₈ O ₆₆ ] ^{m" •} XH ₂ O, e.g.

(A _n ) ^m+ [Cu ₅ (H ₂ O) ₄ ClAs ₂ W ₁₈ O ₆₆ ]" ^{" •} XH ₂ O,

(A _n ) ^m+ [Cu ₅ (H ₂ O) _p X _z Sb ₂ W ₁₈ O ₆₆ ] ^{m" •} XH ₂ O, such as

(A _n ) ^m+ [Cu ₅ (H ₂ O) _p Cl _z Sb ₂ W ₁₈ O ₆₆ ] ^{m" •} XH ₂ O, e.g.

(A _n ) ^m+ [Cu ₅ (H ₂ O) ₄ ClSb ₂ W ₁₈ O ₆₆ ] ¹ " ^{" •} XH ₂ O,

(A _n ) ^m+ [Cu ₅ (H ₂ O) _p X _z Bi ₂ W ₁₈ O ₆₆ ] ^{m" •} XH ₂ O, such as

(A _n ) ^m+ [Cu ₅ (H ₂ O) _p Cl _z Bi ₂ W ₁₈ O ₆₆ ] ^{m" •} XH ₂ O, e.g.

(A _n ) ^m+ [Cu ₅ (H ₂ O) ₄ ClBi ₂ W ₁₈ O ₆₆ ]" ^{" •} XH ₂ O,

(A _n ) ^m+ [Cu _4-5 (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^{m" •} XH ₂ O, e.g.

(A _n ) ^m [Cu _4-5 (H ₂ O) ₄ CIc ₅ X ₂ W ₁₈ O ₆₆ ] ^• XH ₂ O, such as

(A _n ) ^{9^5+} [Cu _4-5 (H ₂ O) ₄ CIo _-5 As ₂ W ₁₈ O ₆₆ ] ⁹ - ^{5" •} xH ₂ 0,

Na(NH ₄ ) _S-5 [Cu _4-5 (H ₂ O) ₄ Cl _0-5 As ₂ W ₁₈ O ₆₆ ] ^• HH ₂ O,

(A _n ) ^{9^5+} [Cu _4-5 (H ₂ O) ₄ Cl _0-5 Sb ₂ W ₁₈ O ₆₆ ] ⁹ - ^{5" •} XH ₂ O,

Na(NH ₄ ) _S-5 [Cu _4-5 (H ₂ O) ₄ Cl _0-5 Sb ₂ W ₁₈ O ₆₆ ] ^• HH ₂ O, or

(A _n ) ^m+ [Cu _4-5 (H ₂ O) _3-5 ClZ ₂ W ₁₈ O ₆₆ ] ^{m" •} XH ₂ O, such as

(A _n ) ¹⁰⁺ [Cu _4-5 (H ₂ O) _3-5 ClBi ₂ W ₁₈ O ₆₆ ] ^{10" •} XH ₂ O, and

Na ₃ (NH ₄ ) ₇ [Cu _4-5 (H ₂ O) ₃₁₅ ClBi ₂ W ₁₈ O ₆₆ ] ^{10" •} 6H ₂ O,

(A _n ) ^m+ [PdCu ₄ L ₄ Z ₂ W ₁₈ O ₆₆ ]" ^{" •} XH ₂ O,

(A _n ) ^m+ [Pd ₂ Cu ₃ L ₃ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^{" •} XH ₂ O,

(A _n ) ^m+ [Pd ₃ Cu ₂ L ₂ Z ₂ W ₁₈ O ₆₆ ]" ^{" •} XH ₂ O,

(A _n ) ^m+ [PtCu ₄ L ₄ Z ₂ W ₁₈ O ₆₆ T ^{" •} XH ₂ O,

(A _n ) ^m+ [Pt ₂ Cu ₃ L ₃ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^{" •} XH ₂ O,

(A _n ) ^m+ [Pt ₃ Cu ₂ L ₂ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^{" •} XH ₂ O,

(A _n ) ^m+ [PdZn ₄ L ₄ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^{" •} XH ₂ O,

(A _n T ⁺ [Pd ₂ Zn ₃ L ₃ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^{" •} XH ₂ O,

(A _n ) ^m+ [Pd ₃ Zn ₂ L ₂ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^{" •} XH ₂ O,

(A _n T ⁺ [PtZn ₄ L ₄ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^{" •} XH ₂ O,

(A _n ) ^m+ [Pt ₂ Zn ₃ L ₃ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^{" •} XH ₂ O, and

(A _n ) ^m+ [Pt ₃ Zn ₂ L ₂ Z ₂ W ₁₈ O ₆₆ ] ¹ " ^{" •} XH ₂ O .

Wherein A, n, m, p, X, z, Z, L, and x are as described above.

The invention is further directed to a process for preparing polyoxometalates of formula (II) :

(A _n T ⁺ [M _γ (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^m" (II)

or solvates thereof, wherein

A represents a cation, n is the number of the cations A, m is the charge of the polyoxoanion,

M represents a transition metal selected from Cu, Zn,

Pd, Pt and mixtures thereof, y is the number of transition metals M and is a number from greater than 4 to less than or equal to 6, al- ternately y is greater than 4 and less than

6, preferably y is about 5, p is the number of water molecules and is a number from

0 to 10,

X is a halide selected from the group consisting of F, Cl, Br, I and mixtures thereof, z is the number of halides and is a number from 0 to 6 and Z is a heteroatom selected from Sb ¹¹¹ , Bi ¹¹¹ , As ¹¹¹ , Se ^IV and Te ^IV ,

comprising:

(a) mixing an aqueous solution of a source of M with

(i) a salt of ((X-ZW ₉ O ₃₃ ) ^w~ or (ii) a Z containing starting material and a salt of WO ₄ ^2" ,

(b) heating the mixture obtained in step (a) ,

(c) optionally cooling the solution obtained in step (b) ,

(d) optionally adding a salt of A and/or a salt of X to the mixture of step (a) or the solution obtained in step (b) or in step (c) to form (A _n ) ^m [My (H ₂ O) _p X _z Z ₂ Wi ₈ O ₆ 6] ^m" or a solvate thereof, and

(e) optionally recovering the polyoxometalate obtained in step (b) , step (c) or step (d) ,

wherein w is the negative charge of the POM-precursor (α- ZW ₉ O ₃₃ ) and is 9 when Z = Sb ¹¹¹ , Bi ¹¹¹ , As ¹¹¹ and 8 when Z = Se ^IV ,

Te ^IV , respectively.

[0034] According to a preferred embodiment, polyoxometalates of formula (I) (i.e. where y is greater than 4 and less than 6) are prepared.

[0035] In step (a) of the process above a source of M is used. Generally, M ²⁺ salts such as CuCl ₂ -2H ₂ O, Cu(CH ₃ COO) ₂ , ZnCl ₂ ,

PdCl ₂ , Pd(CH ₃ COO) ₂ , PdSO ₄ , PtCl ₂ , PtBr ₂ , PtI ₂ and K ₂ PtCl ₄ can be used as a transition metal source. In a preferred embodiment, the Cu source is CuCl ₂ -2H ₂ O, and/or the Zn source is ZnCl ₂ , and/or the Pd source is PdCl ₂ and/or the Pt source is PtCl ₂ . In another preferred embodiment, the Cu source is CuCl ₂ -2H ₂ O, and the Zn source is ZnCl ₂ , and the Pd source is PdCl ₂ and the Pt source is PtCl ₂ .

[0036] This transition metal source is preferably mixed with (i) a salt of (α-ZW ₉ θ33) ^w~ or (ii) a Z containing starting mate- rial, such as Z ₂ O ₃ or H ₂ ZO ₃ (e.g. Sb ₂ O ₃ , Bi ₂ O ₃ , H ₂ SeO ₃ ) or a salt of Z ³⁺ or Z ⁴⁺ , and a salt of WO ₄ ^2- (where Z is selected from Sb ¹¹¹ , Bi ¹¹¹ , As ¹¹¹ , Se ^IV and Te ^IV ) . It is convenient to react the transition metal source with (i) a salt of polyoxometalate precursor (α-ZW ₉ O ₃₃ ) ^w~ . It has been found that the course of this reaction can be controlled by various parameters such as pH of the aqueous solution, concentration and ratio of the starting materials and the counterions used in step (a) as well as the reaction temperature used in step (b) . [0037] Advantageously, the pH of the aqueous solution used in step (a) is a number from 4.5 to 7.5, alternately from 4.5 to 6.5 and preferably from 4.5 to 5.5. A pH of about 4.8 is particularly useful. Generally, a buffer solution can be used for adjusting the pH. It is particularly useful to select an ammonium acetate buffer having a concentration of 0.5 M and a pH of about 4.8 as an aqueous solvent.

[0038] In addition, the ratio of the starting materials is considered to have an effect on the preparation of the present POMs. In a preferred embodiment, the molar ratio of the transition metal ions originating from the transition metal source to the salt of (α-ZW ₉ O ₃₃ ) ^w~ ranges from 1.5:1 to 30:1 and preferably from 2:1 to 15:1.

[0039] Suitable cations in the salts of the polyanion (α- ZW ₉ O ₃₃ ) ^w~ used in step (a) are for example lithium, sodium, po-

tassium, ammonium, guanidinium, tetraalkylammonium, protonated aliphatic amines and protonated aromatic amines. It has been found that when alkaline metals such as sodium or potassium are present in the reaction mixture of step (a) , these cations may occupy some of the addenda positions of the central belt of the resulting polyanion. Thus, in order to prepare poly- oxometalates having a high level of transition metal centers, e.g. 5 Cu centers incorporated per POM molecule, it is advisable to avoid alkaline metals and use the ammonium salt of (α- ZW ₉ θ33) ^w~ in step (a) . Consequently, it is advantageous if steps (a) and (b) of the process according to the invention are performed in the absence of alkali ions. If alkali ions are nevertheless present during step (a) and (b) , then it is preferred to use sodium. [0040] Moreover, in step (a) it is advantageous that the salt of (α-ZW ₉ θ33) ^9~ is added to an aqueous solution of the transition metal source. It is particularly advantageous that this addition is performed quickly. [0041] In step (b) , the mixture obtained in step (a) is typi- cally heated to a reaction temperature of 50 to 100 ⁰ C, preferably 70 to 90 ⁰ C. Depending on the size of the batch the heating step may be performed for about 30 to about 120 min or longer, typically for about 45 to 75 minutes, usually for about 60 min. [0042] Optionally, in step (c) the heated reaction mixture of step (b) is cooled, typically to room temperature (approx 23 ⁰ C) , and optionally filtered.

[0043] Furthermore, in step (d) a salt of the cation A and/or a salt of X can be added to the mixture of step (a) or to the solution obtained in step (b) or step (c) or, in case of filtration in step (c) , to its filtrate to form (A _n ) ^m [M _y (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^m" (where A, n, m, M, y, p, X, z, and Z are as defined above in formula II) . In a preferred embodiment,

the salt of A and/or the salt of X is added as a solid or in the form of an aqueous solution. The counterions of A can be selected from the group consisting of any stable, non- reducing, water soluble anion, e.g. halides, nitrate, sulfate, acetate. In a preferred embodiment, the chloride salt is used. The counterions of X can be selected from alkali or ammonium. However, the addition of extra cations A and/or extra halides in step (d) is not necessary if the desired cations and halides are already present during step (a) , for example as a counterion of (0,-ZW ₉ O ₃₃ ) ^w~ or a component of the transition metal source. In some embodiments, all desired cations and anions are already present during step (a) and thus step (d) is preferably not performed. [0044] In step (e) , the polyoxometalates according to the in- vention formed in step (b) , (c) or (d) can be recovered. For example, isolation and recovery of the POMs can be effected by common techniques including bulk precipitation or crystallization . [0045] The polyoxometalates described herein (and their sol- vates) are preferably used for catalyzing homogeneous and heterogeneous oxidation reactions of organic substrates. Specifically in a preferred embodiment this invention relates to a process to oxidize organic substrates comprising contact one or more organic substrates with a polyoxometalate represented by the formula:

(A _n ) ^m+ [M _γ (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^m" (II)

or solvates thereof, wherein

A represents a cation, n is the number of the cations A, m is the charge of the polyoxoanion,

M represents a transition metal selected from Cu, Zn, Pd, Pt and mixtures thereof,

y is the number of transition metals M and is a number greater than 4 and less than or equal to 6, p is the number of water molecules and is a number from

0 to 10, X is a halide selected from the group consisting of F,

Cl, Br, I and mixtures thereof, z is the number of halides and is a number from 0 to 6 and

Z represents a heteroatom selected from Sb ¹¹¹ , Bi ¹¹¹ , As ¹¹¹ , Se ^IV and Te ^Iv .

[0046] Preferably, polyoxometalates of formula (I) (i.e. where y is greater than 4 and less than 6) can be used for catalyzing homogeneous and heterogeneous oxidation reactions of or- ganic substrates.

[0047] In particular, the present POMs can be used for oxidizing unsubstituted and substituted hydrocarbons such as branched or unbranched alkanes and alkenes having carbon numbers from Cl to C20 (preferably from Cl to C6) , cycloalkanes, cycloalkenes, aromatic hydrocarbons or mixtures thereof. Examples of suitable organic substrates are methane, ethane, propane, butane, isobutane, pentane, isopentane, neopentane, hexane, ethylene, propylene, α-butylene, cis-β-butylene, trans- β-butylene, isobutylene, n-pentylene, isopentylene, cyclohex- ane, adamantane, cyclooctadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, mesitylene, durene, hexamethylbenzene, naphthalene, anthracene, phenantrene and mixtures thereof. [0048] Since their terminal water ligands are substitution labile, the coordination sites of the transition metals are eas- ily accessible to the organic substrate and the oxygen transfer molecule and therefore high catalytic activities are achieved. Further, the remarkable thermal stability of the polyoxoxmetalates permits their use under a great variety of reaction conditions.

[0049] Commonly, suitable oxygen donors such as molecular oxygen, peroxides (e.g. H ₂ O ₂ , t- (C ₄ H ₉ )OOH) or peracids (e.g. CH ₃ COOOH) can be used as oxidizing agent. Preferably, the oxidizing agent is an oxygen containing atmosphere. In particu- lar, the oxygen containing atmosphere is air and is preferably constantly passed through the organic substrate (such as an alkane or alkene) at a pressure of 0.01 to 100 bar, preferably 10 to 70 bar. [0050] Moreover, in some embodiments, the oxidation of the or- ganic substrate is preferably carried out at a temperature of 30 to 600 ⁰ C, preferably 75 to 250 ⁰ C, preferably 130 to 180 °C. In a particularly useful embodiment the oxidation is carried out at a temperature of 100 ⁰ C or more, alternately 110 ⁰ C or more, alternately 120 ⁰ C or more, alternately 130 ⁰ C or more, alternately 140 ⁰ C or more, alternately 150 ⁰ C or more, alternately 160 ⁰ C or more, alternately 170 ⁰ C or more, alternately 180°C or more, alternately 190°C or more, alternately 200°C or more, alternately 210 ⁰ C or more, alternately 220 ⁰ C or more. [0051] Prior to their use in oxidation reactions, the present polyoxometalates can be supported on a solid support. Suitable supports include materials having a high surface area and a pore size which is sufficient to allow the polyoxometalates to be loaded, e.g. aerogels of aluminum oxide and magnesium oxide, titanium oxide, zirconium oxide, silica, mesoporous silica (such as SBA-15) , active carbon, zeolites and mesoporous zeolites. In another embodiment, the supported polyoxometalates are further calcined at a temperature not exceeding the transformation temperature of the polyoxometalate, i.e. the temperature at which decomposition of the polyoxometalate starts to take place (usually about 500 to 600 ⁰ C for the present POMs) .

[0052] Due to the definite stoichiometry of polyoxometalates, the present POMs can be converted (e.g. by calcination at a temperature exceeding the transformation temperature) to mixed

metal oxide catalysts in a highly reproducible manner. Consequently, the polyoxometalates according to the invention can also be used as a precursor for mixed metal oxide catalysts such as so-called Mitsubishi-type catalysts which are particu- larly useful for the oxidation of hydrocarbons such as propane .

[0053] Another useful aspect of this invention is that the polyoxometalates (supported or unsupported) described herein can be recycled and used multiple times for the oxidation of organic molecules.

[0054] For example the POMs produced herein can be collected after an oxidation reaction, washed with a polar or non-polar solvent, such as acetone then dried under heat (typically 50 ⁰ C or more, alternately 100 ⁰ C or more, alternately 125°C or more, alternately 150 ⁰ C or more) for 30 minutes to 48 hours, typically for 1 to 24 hours, more typically for 2 to 10 hours, more typically for 3 to 5 hours. The recycled supported POMs may be used on fresh organic molecules (such as hexadecane) or on recycled organic molecules from a recycle stream. [0055] Advantageously, the supported polyoxometalates may be recycled and used again under the same or different reaction conditions. Typically the supported POMs are recycled at least 1 time, preferably at least 4 times, preferably at least 8 times, preferably at least 12 times, preferably at least 100 times.

[0056] Thus, in a particularly useful embodiment, this invention relates to a process to oxidize organic substrates (typically an alkane) comprising contacting a first organic substrate with one or more polyoxometalates described herein, thereafter recovering the polyoxometalates, contacting the polyoxometalates with a solvent (such as acetone) at a temperature of 50 ⁰ C or more to obtain a recycled polyoxometalate, thereafter contacting the recycled polyoxometalate with a second organic substrate, which may be the same as or different

from the first organic substrate, this process may be repeated many times, preferably at least 4 times, preferably at least 8 times, preferably at least 12 times, preferably at least 100 times . [0057] This invention further relates to:

1. Polyoxometalates represented by the formula I

(A _n ) ^m+ [M _γ (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^m" (I) or solvates thereof, wherein

A represents a cation, n is the number of the cations A, m is the charge of the polyoxoanion,

M represents a transition metal selected from Cu, Zn,

Pd, Pt and mixtures thereof, y is the number of transition metals M and based on all polyoxometalate molecules of a given sample, Y represents an average value of greater than 4 and less than 6 (preferably Y is a number from greater than 4 to less than 6) , p is the number of water molecules and varies from 0 to 10 (preferably P is a number from 0 to 10),

X is a halide selected from the group consisting of F,

Cl, Br, I and mixtures thereof, z is the number of halides and varies from 0 to 6

(preferably P is a number from 0 to 6) , and Z represents a heteroatom selected from Sb ¹¹¹ , Bi ¹¹¹ , As ¹¹¹ , Se ^IV and Te ^Iv .

2. The polyoxometalates according to paragraph 1, wherein y has a value of more than 4 and less than 5.

3. The polyoxometalates according to paragraph 1 or 2, wherein y has a value of about 4.5.

4. The polyoxometalates according to paragraph 1, wherein for substantially all polyoxometalate molecules y is 5.

5. The polyoxometalates according to any one of paragraphs 1 to 4, wherein M is Cu. 6. The polyoxometalates according to any one of paragraphs 1 to 5, wherein A is selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, magnesium,

calcium, strontium, barium, titanium, vanadium, chromium, lanthanum, lanthanide metal, actinide metal, manganese, iron, cobalt, nickel, copper, zinc, ruthenium, palladium, platinum, tin, antimony, tellurium, phosphonium, ammonium, guanidinium, tetraalkylammonium, protonated aliphatic amines, protonated aromatic amines or combinations thereof .

7. The polyoxometalates according to paragraph 5 or 6, represented by the formula (A _n ) ^m+ [CU _y (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^{m" •} XH ₂ O, wherein x represents the number of hydrate water molecules per polyoxometalate molecule, exclusive of water molecules which are bound as ligands to Cu or optionally A positioned in the framework. 8. A process for the preparation of polyoxometalates of formula (II)

(A _n ) ^m+ [M _y (H ₂ O) _p X _z Z ₂ W ₁₈ O ₆₆ ] ^m" (II) or solvates thereof, wherein

A represents a cation, n is the number of the cations A, m is the charge of the polyoxoanion,

M represents a transition metal selected from Cu, Zn,

Pd, Pt and mixtures thereof, y is the number of transition metals M and based on all polyoxometalate molecules of a given sample, Y represents an average value of greater than 4 and less than 6 (preferably Y is a number from greater than 4 to less than 6) , p is the number of water molecules and varies from 0 to 10 (preferably P is a number from 0 to 10),

X is a halide selected from the group consisting of F,

Cl, Br, I and mixtures thereof, z is the number of halides and varies from 0 to 6

(preferably P is a number from 0 to 6) , and Z represents a heteroatom selected from Sb ¹¹¹ , Bi ¹¹¹ , As ¹¹¹ , Se ^IV and Te ^IV ,

comprising:

(a) mixing an aqueous solution of a source of M with

(i) a salt of (α-ZW ₉ O ₃₃ ) ^w~ or

(ii) a Z containing starting material and a salt of WO ₄ ^2" ,

(b) heating the mixture obtained in step (a) ,

(c) optionally cooling the solution obtained in step (b) ,

(d) optionally adding a salt of A and/or a salt of X to the mixture of step (a) or the solution obtained in step (b) or in step (c) to form (A _n ) ^m+

[My (H ₂ O) pX _z Z ₂ W ₁₈ O ₆ 6] ^m" or a solvate thereof, and (d) optionally recovering the polyoxometalate obtained in step (b) , step (c) or step (d) , wherein w is the negative charge of the POM-precursor (α- ZW ₉ O ₃₃ ) and is 9 when Z = Sb ¹¹¹ , Bi ¹¹¹ , As ¹¹¹ and 8 when Z =

Se ^IV , Te ^IV , respectively.

9. The process according to paragraph 8, wherein the poly- oxometalates of formula (II) are polyoxometalates of formula (I) according to any one of paragraphs 1 to 7. 10. The process according to paragraph 8 or 9, wherein the source of M is selected from the group consisting of CuCl ₂ -2H ₂ O, Cu(CH ₃ COO) ₂ , ZnCl ₂ , PdCl ₂ , Pd(CH ₃ COO) ₂ , PdSO ₄ , PtCl ₂ , PtBr ₂ , PtI ₂ and K ₂ PtCl ₄ and preferably is CuCl ₂ -2H ₂ O.

11. The process according to any one of paragraphs 8 to 10, wherein the pH of the aqueous solution used in step (a) ranges from 4.5 to 7.5, preferably from 4.5 to 6.5 and more preferably from 4.5 to 5.5.

12. The process according to paragraph 11, wherein in step (a) an ammonium acetate buffer having a concentration of about 0.5 M is used as aqueous solvent.

13. The process according to any one of paragraphs 8 to 12, wherein in step (a) (i) the molar ratio of transition metal ions originating from the source of M to the salt of (α- ZW ₉ O ₃₃ ) ^w~ ranges from 1.5:1 to 30:1 and preferably from 2:1 to 15:1.

14. The process according to any one of paragraphs 8 to 13, wherein in step (a) (i) the ammonium salt of (α-ZW ₉ O ₃₃ ) ^w~ is used.

15. The process according to any one of paragraphs 8 to 14, wherein steps (a) and (b) are performed in the absence of alkali ions.

16. The process according to any one of paragraphs 8 to 15, wherein in step (b) the mixture is heated to a temperature of 50 to 100 ⁰ C, preferably from 70 to 90 ⁰ C.

17. The process according to any one of paragraphs 8 to 16, wherein in step (e) the product is isolated by bulk precipitation or crystallization. 18. The use of a polyoxometalate according to any one of paragraphs 1 to 7 or prepared according to any one of paragraphs 8 to 17 as catalyst for the homogeneous or heterogeneous oxidation of organic substrates.

19. The use according to paragraph 18, wherein the organic substrates are unsubstituted or substituted hydrocarbons such as branched or unbranched alkanes and alkenes having carbon numbers from Cl to C20, cycloalkanes, cycloalkenes, aromatic hydrocarbons or mixtures thereof.

20. The use according to paragraph 18 or 19, wherein the poly- oxometalate is supported on a solid support.

21. The use according to paragraph 20, wherein the supported polyoxometalate is calcined at a temperature not exceeding the transformation temperature of the polyoxometalate.

22. The use of a polyoxometalate according to any one of para- graphs 1 to 7 or prepared according to any one of paragraphs 8 to 17 as a precursor for preparing mixed metal oxide catalysts.

23. The use according to paragraph 22, wherein the mixed metal oxide catalysts are Mitsubishi-type catalysts. 24. A process of oxidizing an organic substrate comprising contacting a polyoxometalate according to any one of paragraphs 1 to 7 or prepared according to any one of paragraphs 8 to 17 as catalyst with an organic substrate. 25. The process of paragraph 24 wherein the organic substrate is unsubstituted or substituted hydrocarbons such as branched or unbranched alkanes and alkenes having carbon numbers from Cl to C20, cycloalkanes, cycloalkenes, aromatic hydrocarbons or mixtures thereof.

26. The process of paragraph 24 or 25, wherein the polyoxome- talate is supported on a solid support.

27. The process of paragraph 26, wherein the supported poly- oxometalate is calcined at a temperature not exceeding the transformation temperature of the polyoxometalate .

28. The process of any of paragraphs 24 to 27 wherein an oxy ^¬ gen donor is present during the oxidation.

29. The process of paragraph 28 wherein air is constantly passed through the organic substrate during the oxidation. 30. The process of any of paragraphs 24 to 29 wherein the oxi ^¬ dation takes place at a temperature of 30 to 600 ⁰ C.

31. The process of any of paragraphs 24 to 29 further com ^¬ prising 1) recovering the polyoxometalates, 2) contacting the polyoxometalates with a solvent at a temperature of 50 ⁰ C or more to obtain a recycled polyoxometalate, 3) thereafter contacting the recycled polyoxometalate with a second organic substrate, which may be the same or dif ^¬ ferent than the first organic substrate.

32. The process of paragraph 31 wherein the polyoxometalate is recycled at least 4 times, preferably at least 8 times, preferably at least 12 times, preferably at least 100 times. [0058] The invention is further illustrated by the following examples . Example 1: Na (NH ₄ ) ₈ .s [Cu ₄ . ₅ (H ₂ O) 4Cl ₀ .5 (ASW9O33) 2] ^• HH ₂ O

[0059] A 0.31 g (0.13 mmol) sample of (NH ₄ J ₉ [AsW ₉ O ₃₃ ] was added with stirring to a solution of 0.22 g (1.30 mmol) CuCl ₂ -H ₂ O in 20 mL of a 0.5 M NH ₄ OAc buffer (pH 4.8). This solution was heated to 80 ⁰ C for 1 h and then cooled to room temperature and filtered. Addition of a few drops of 0.1 M NaCl and slow evaporation in an open vial resulted in 0.23 g (yield 68%) of green crystalline material suitable for X-ray diffraction. [0060] IR (cm-1) : 1400, 968 (sh) , 948, 904, 862 (sh), 789(sh), 749 (sh), 736, 629, 568, 484, 453 (measured on a Nicolet-Avatar 370 spectrometer using KBr pellets) .

[0061] Besides IR the product was also characterized by single crystal XRD. The crystal data and structure refinement ob ^¬ tained on a Bruker Kappa APEX II instrument using the SHELXTL software package are shown in the following table.

Table 1. Crystal data and structure refinement for Na (NH ₄ ) 8.5 [Cu ₄ .5 (H ₂ O) ₄ Cl ₀ . ₅ (AsW ₉ O ₃₃ ) 2] -HH ₂ O.

Empirical formula As ₂ CIo.5 Cu ₄ .5 Hδ ₄ Ng _-5 Na Osi Wig Formula weight 5265.5

Temperature 173(2) K

Wavelength 0.71073 A

Crystal system Tetragonal

Space group P-42(l)m Unit cell dimensions a = 16.8113(14) A α= 90°. b = 16.8113 (14) A β= 90° . c = 13.9215 (16) A γ = 90°.

Volume 3934.5(6) A ³

Z 2 Density (calculated) 4.398 Mg/m ³

Absorption coefficient 28.359 mm ^~ l

F(OOO) 4520

Crystal size 0.05 x 0.06 x 0.09 mm ³

Theta range for data collection 1.71 to 28.32°. Index ranges -22<=h<=22, -22<=k<=22, -18<=1<=18

Reflections collected 41736

Independent reflections 5128 [R(int) = 0.0827]

Completeness to theta = 28.32° 99.8 %

Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.2628 and 0.1598

Refinement method Full-matrix least-squares on F ²

Data / restraints / parameters 5128 / 0 / 174

Goodness-of-fit on F ² 1.004

Final R indices [I>2sigma (I) ] Rl = 0.0371, wR2 = 0.0667 R indices (all data) Rl = 0.0442, wR2 = 0.0682

Absolute structure parameter 0.02(2)

Largest diff. peak and hole 1.904 and -1.937 e.A ^~3

[0062] The atomic coordinates as well as the equivalent isotropic displacement parameters which are defined as one third of the trace of the orthogonalized U ^1D tensor are shown in Table 2.

Table 2. Atomic coordinates x, y and z (-10^ A) and equivalent isotropic displacement parameters U(eq) (-1O ³ A ² ) for Na (NH ₄ ) 8.5 [Cu ₄ .5 (H ₂ O) ₄ Cl ₀ . ₅ (AsW ₉ O ₃₃ ) 2] -HH ₂ O.

y U(eq)

W(I) 3007(1) 581(1) -298(1) 14(1)

W(2) 2954(1) 504(1) 4077(1) 15(1)

W(3) 2243(1) -193(1) 1987(1) 14(1)

W(4) 2540(1) 2460(1) 386(1) 16(1)

W(5) 1775(1) 1668(1) 2696(1) 16(1)

As(I) 3885(1) 1115(1) 1915(2) 11(1)

Cu(I) 5000 0 3924(3) 16(1)

Cu(2) 3977(1) -1023(1) 908(2) 14(1)

Cu(3) 5000 0 -36(6) 29(2)

Cu(4) 4012(3) -988(3) 2898(5) 45(2)

Cl(I) 5000 0 5779(14) 46(5)

Na(I) 0 0 5000 36(3)

0(1) 884(5) 2108(5) 2987(7) 21(2)

0(2) 2477(5) 2523(5) 3030(10) 22(3)

0(3) 3200(5) -677(5) 1828(6) 15(2)

0(4) 3559(5) 1441(5) 4307(9) 12(3)

0(5) 1593(6) -947(6) 1798(7) 24(2)

0(6) 5000 0 -1568(18) 47(7)

0(7) 2322(5) -258(5) 3363(6) 16(2)

0(8) 3509(5) 1491(5) 823(9) 14(3)

0(9) 3777(5) 1223(5) -989(9) 12(3)

O(IO) 2331(5) 248(5) 746(6) 16(2)

0(11) 1872(6) 3128(6) -94(9) 20(3)

0(12) 2598(6) 80(6) -1252(7) 21(2)

0(13) 1431(5) 650(5) 2232(6) 17(2)

0(14) 2752(6) 185(6) 5226(7) 23(2)

0(15) 2025(5) 1204(5) 3914(6) 13(2)

0(16) 4085(5) 2064(5) 2479(6) 12(2)

0(17) 3852(5) -13(6) 3772(7) 18(2)

0(18) 1890(5) 2003(5) 1372(6) 18(2)

0(19) 2320(5) 1551(5) -352(7) 17(2)

0(20) 3794(5) -101(6) 139(6) 17(2)

0(1 W) 3825(7) -1175(7) 8069(15) 52(5)

0(2W) 866(7) 1108(7) 5323(8) 42(3)

0(3W) 2460(10) -2540(10) 2256(19) 106(9)

0(4W) 1356(13) 3644(13) 4130(20) 123(10)

0(5W) 0 0 3177(13) 48(5)

0(6W) 3834(9) 1166(9) -3045(18) 84(7)

0(7W) 747(7) 912(7) 178(8) 41(3)

0(8W) 3271(10) -1729(10) 3633(16) 89(8)

0(9W) 1935(9) 760(9) 6903(12) 9(3)

Example 2 : Na ( NH ₄ ) 8 . 5 [ CU ₄ . 5 ( H ₂ O ) ₄ C l ₀ . 5 ( SbW ₉ O ₃ S ) ₂ ] - HH ₂ O

[0063] Example 1 was repeated with the exception that instead of 0.31 g (0.13 mmol) of (NH ₄ J ₉ [AsW ₉ O ₃₃ ] 0.32 g (0.13 mmol) of (NH ₄ ) ₉ [SbW ₉ O ₃₃ ] was used. The yield obtained was 0.24 g (69 %) of green crystalline material suitable for X-ray diffraction. [0064] IR (cm-1) : 1402, 944, 897, 848, 773 (sh) , 731, 638, 568, 476, 447 (measured on a Nicolet-Avatar 370 spectrometer using KBr pellets) .

[0065] The crystal data and structure refinement obtained on a Bruker Kappa APEX II instrument using the SHELXTL software package are shown in the following table.

Table 3. Crystal data and structure refinement for Na (NH ₄ ) ₈ . ₅ [Cu _4-5 (H ₂ O) ₄ Cl ₀ . ₅ (SbW ₉ O ₃₃ ) ₂ ] -HH ₂ O.

Empirical formula Cl ₀ .5 Cu _{4 - 5} H ₆₄ N ₈ .5 Na O ₈ i Sb ₂ W ₁₈ Formula weight 5359.2 Temperature 173(2) K Wavelength 0.71073 A Crystal system Tetragonal

Space group P-42 (l)m

Unit cell dimensions a = 16.8129 (9) A α= 90°. b = 16.8129(9) A β= 90°. c = 13.9898 (11) A γ = 90°.

Volume 3954.5(4) A ³

Z 2

Density (calculated) 4.454 Mg/m ³

Absorption coefficient 28.054 mm ^"1

F(OOO) 4592

Crystal size 0.08 x 0.08 x 0.09 mm ³

Theta range for data collection 1.89 to 28.30°.

Index ranges -22<=h<=22, -22<=k<=22, -18<=1<=18

Reflections collected 42047

Independent reflections 5155 [R(int) = 0.0757]

Completeness to theta = 28.30° 99.9 %

Absorption correction Semi-empirical from equivalents

Max. and min. transmission 0.2627 and 0.1615

Refinement method Full-matrix least-squares on F^

Data / restraints / parameters 5155 / 0 / 174

Goodness-of-fit on F^ 1.019

Final R indices [I>2sigma (I) ] Rl = 0.0364, wR2 = 0.0757

R indices (all data) Rl = 0.0406, wR2 = 0.0771

Absolute structure parameter 0.020(16)

Largest diff. peak and hole 2.060 and -2.716 e.A ^~3

[0066] The atomic coordinates as well as the equivalent isotropic displacement parameters which are defined as one third of the trace of the orthogonalized U ^1D tensor are shown in Table 4.

Table 4. Atomic coordinates x, y and z (-10^ A) and equivalent isotropic displacement parameters U(eq) 10 ^J A ² ) for Na (NH ₄ ) 8.5 [Cu ₄ .5 (H ₂ O) ₄ Cl ₀ . ₅ (SbW ₉ O ₃₃ ) 2] -HH ₂ O.

y U(eq)

W(I) 3007(1) -587(1) -9699(1) 12(1) W(2) 2946(1) -499(1) -14062(1) 14(1) W(3) 2235(1) 193(1) -11988(1) 13(1)

W(4) -2548(1) -2453(1) -10387(1) 14(1)

W(5) -1783(1) -1657(1) -12690(1) 14(1)

Sb(I) -3980(1) -1020(1) -11911(1) 9(1)

Cu(I) -5000 O -13939(2) 13(1)

Cu(2) -3962(1) 1038(1) -10891(2) 12(1)

Cu(3) -5000 O -9957(7) 43(2)

Cu(4) -3987(3) 1013(3) -12887(6) 52(2)

Na(I) O O -15000 37(3)

Cl(I) -5000 O -15739(13) 38(4)

0(1) -894(5) -2118(6) -12973(7) 21(2)

0(2) -2502(5) -2498(5) -13020(10) 19(3)

0(3) -3193(5) 680(5) -11824(7) 17(2)

0(4) -3551(5) -1449(5) -14281(9) 14(3)

0(5) -1572(5) 953(6) -11788(7) 20(2)

0(6) -5000 O -8451(19) 50(7)

0(7) -2311(5) 273(5) -13361(6) 14(2)

0(8) -3520(5) -1480(5) -10774(9) 14(3)

0(9) -3790(5) -1210(5) -9004(9) 13(3)

0(10) -2336(5) -255(5) -10749(6) 12(2)

0(11) -1865(6) -3135(6) -9936(10) 22(3)

0(12) -2602(6) -77(6) -8760(7) 23(2)

0(13) -1407(5) -645(5) -12236(6) 14(2)

0(14) -2759(6) -179(6) -15208(7) 23(2)

0(15) -2022(5) -1194(5) -13912(6) 12(2)

0(16) -4115(5) -2091(5) -12500(6) 13(2)

0(17) -3847(6) 9(6) -13731(7) 17(2)

0(18) -1921(6) -1998(6) -11386(7) 17(2)

0(19) -2311(5) -1563(5) -9627(7) 17(2)

0(20) -3785(6) 94(6) -10150(7) 19(2)

0(1 W) -3821(8) 1179(8) -18113(15) 50(5)

0(2W) -1930(9) -767(9) -16883(12) 6(3)

0(3W) -871(7) -1082(7) -15331(9) 39(3)

0(4W) -2460(10) 2540(10) -12207(18) 81(7)

0(5W) -1360(14) -3640(14) -14050(20) 125(12)

0(6W) O O -13187(14) 51(5)

0(7W) -3808(9) -1192(9) -6951(18) 73(7)

0(8W) -748(7) -922(7) -10199(9) 41(3)

0(9W) -3281(11) 1719(11) -13568(18) 86(8)

Example 3: Na ₃ (NH ₄ ) 7 [Cu ₄ . ₅ (H ₂ O) ₃ . ₅ C1 (BiW ₉ O ₃ S) 2] ^• 6H ₂ O

[0067] A 0.34 g (0.13 mmol) sample of Na ₉ [BiW ₉ O ₃₃ ] was added with stirring to a solution of 0.22 g (1.30 mmol) CuCl ₂ -H ₂ O in 20 mL of a 0.5 M NH ₄ OAc buffer (pH 4.8). This solution was heated to 80 ⁰ C for 1 h and then cooled to room temperature and filtered. Slow evaporation in an open vial resulted in 0.24 g (yield 67%) of green crystalline material suitable for X-ray diffraction.

[0068] IR (cm ^"1 ): 1402, 940, 889, 836, 760 (sh), 722, 649(sh), 566, 502, 438 (measured on a Nicolet-Avatar 370 spectrometer using KBr pellets) . [0069] The crystal data and structure refinement obtained on a Bruker Kappa APEX II instrument using the SHELXTL software package are shown in the following table.

Table 5 . Crys tal data and s tructure re f inement for Na ₃ (NH ₄ ) 7 [ Cu ₄ .5 ( H ₂ O ) 3.5CI ( BiW ₉ O ₃₃ ) 2 ] ^• 6H ₂ O .

Empi ri cal formula Bi ₂ Cl Cu _{4 - 5} H ₄₇ N ₇ Na ₃ O _{75 - 5} W ₁₈ Formula weight 5471 . 2

Temperature 173(2) K

Wavelength 0.71073 A

Crystal system Tetragonal

Space group P-42(l)m Unit cell dimensions a = 16.8295(4) A α= 90°. b = 16.8295 (4) A β= 90° . c = 13.7918 (6) A γ = 90°.

Volume 3906.3(2) A ³

Z 2 Density (calculated) 4.600 Mg/m ³

Absorption coefficient 32.170 rm ^" ^

F(OOO) 4651

Crystal size 0.20 x 0.05 x 0.05 mm ³

Theta range for data collection 1.48 to 26.39°. Index ranges -21<=h<=21, -21<=k<=21, -13<=1<=17

Reflections collected 62884

Independent reflections 4196 [R(int) = 0.1424]

Completeness to theta = 26.39° 99.7 %

Absorption correction Semi-empirical from equivalents Max. and min. transmission 0.2961 and 0.1130

Refinement method Full-matrix least-squares on F ²

Data / restraints / parameters 4196 / 0 / 156

Goodness-of-fit on F ² 1.038

Final R indices [I>2sigma (I) ] Rl = 0.0421, wR2 = 0.1192 R indices (all data) Rl = 0.0495, wR2 = 0.1339

Absolute structure parameter -0.02(2)

Largest diff. peak and hole 12.518 and -2.444 e.A ^~3

[0070] The atomic coordinates as well as the equivalent iso- tropic displacement parameters which are defined as one third of the trace of the orthogonalized U ^1D tensor are shown in Table 6.

Table 6. Atomic coordinates x, y and z (-10^ A) and equivalent iissoottrrooppiicc ddiissppllaacceemmeenntt ppaarraammeetteerrss UU((«eq) (-1O ³ A ² ) for Na ₃ (NH ₄ ) 7 [Cu ₄ .5 (H ₂ O) 3.5CI (BiW ₉ O ₃₃ ) 2] ^• 6H ₂ O.

y U(eq)

W(I) 3352(1) 3203(1) 2710(1) 17(1)

W(2) 4503(1) 2050(1) 4088(1) 17(1)

W(3) 5189(1) 2766(1) 2001(1) 16(1)

W(4) 4405(1) 1994(1) -319(1) 15(1)

W(5) 2555(1) 2445(1) 373(1) 16(1)

Bi(I) 4041(1) 959(1) 1915(1) 14(1)

Cu(I) 5000 0 3977(4) 18(1)

Cu(2) 6043(2) 1043(2) 874(3) 14(1)

Cu(3) 6332(3) 1332(3) 3188(4) 20

Cl(I) 5000 0 5862(15) 66(5)

0(1T) 2903(9) 4083(9) 3007(11) 23(3)

O(IA) 2515(8) 2485(8) 3050(14) 15(4)

O(2A) 4855(10) 2218(10) 5245(12) 27(4)

O(2T) 3544(9) 1456(9) 4323(16) 21(5)

O(3T) 5953(9) 3449(9) 1794(10) 19(3)

O(4A) 3800(9) 1200(9) -1077(14) 16(4)

O(4T) 4947(10) 2428(9) -1271(11) 22(3)

O(5A) 2310(8) 1532(8) -427(10) 15(3)

O(5T) 1890(8) 3110(8) -63(14) 17(4)

O(lBl) 4123(8) 2114(8) 2516(9) 9(3)

0(12) 3804(10) 2997(10) 3975(11) 25(3)

0(13) 4366(10) 3593(9) 2290(12) 24(3)

0(15) 3020(9) 3068(9) 1393(12) 23(3)

0(2Bl) 3502(8) 1498(8) 724(14) 14(4)

0(2Cl) 5013(10) 1136(10) 3741(11) 23(3)

0(23) 5308(9) 2677(9) 3403(10) 17(3)

O(3C2) 5645(9) 1777(9) 1854(11) 23(3)

0(34) 4730(8) 2655(9) 734(10) 17(3)

O(4C2) 5056(9) 1227(9) 151(10) 19(3)

Na(I) 6011(15) 1011(15) 2940(20) 20

Na(2) 5000 0 -655(12) 20

Na(3) 5000 5000 5000 39(5)

0(1 W) 5000 5000 6800(20) 44(7)

0(2W) 5841(11) 3906(11) 4670(13) 36(4)

0(3W) 5758(12) 4073(12) -195(15) 43(5)

0(4W) 3070(14) 5738(14) 3088(17) 55(5) 0(5W) 6149(15) 1149(15) -1890(20) 58(8)

[0071] All documents described herein are incorporated by reference herein, including any priority documents and/or testing procedures, except to the extent they are inconsistent with this specification. As is apparent from the foregoing general description and the specific embodiments, while forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited thereby. Likewise, the term "comprising" is considered synonymous with the term "including" for purposes of Australian law.