The present invention relates to nickel tris-pyrazolyl borate complexes, their preparation, a homogeneous catalyst which contains them and its use in the homo-, co-and ter- polymerization of a-olefins.

More specifically, the present invention relates to particular nickel tris-pyrazolyl borates, and also to a ho- mogeneous catalyst comprising said complexes and their use in the homo-, co-and ter-polymerization of ethylene.

The polymers of a-olefins, and in particular of ethyl- ene, are important commercial products which have numerous applications. For example, polyolefins with a low molecular weight are used as lubricants and in waxes, whereas polyolefins with a higher molecular weight are used for fi- bres, films, elastomers, etc.

It is known that olefins can be polymerized using soluble compounds of transition metals combined with de- rivatives of aluminum. Typical compounds of transition met-

als, for example Ti, Zr, Hf, are those in which the metal is complexed with a polydentate organic ligand which does not take part in the polymerization reaction, but contrib- utes to blocking some of the co-ordination sites of the metal, whereas the others are occupied by ligands which are freed at the appropriate moment making the co-ordination site available for the polymerization reaction.

Patent application WO 98/30609 describes catalytic components essentially consisting of complexes of Nickel allyl bis-pyrazolyl borates ; in particular, these are a nickel allyl bis-3-benzopyrazolyl borate and nickel allyl 3-i-propyl-pyrazolyl-di-phenyl-borate.

These catalytic components can be activated with Lewis acids of the B (C6H5) 3 and B (C6F5) 3 type. The catalytic activ- ity of these components however is unsatisfactory. In par- ticular, in spite of the high ethylene pressures (6.9 MPa) and particularly long reaction times (18 hours) in the po- lymerization of ethylene, the activity of these precursors is low (from 310 to 590 moles of PE/mole of Ni) and in cer- tain cases is equal to zero.

A new group of nickel tris-pyrazolyl borate complexes has now been found which overcomes the disadvantages de- scribed above. The use of these complexes as components of ; catalytic systems for the polymerization of olefins advan- tageously allows polymers to be obtained with a high yield,

using limited quantities of cocatalyst and does not require high ethylene pressures.

In accordance with this, an objective of the present invention relates to a nickel tris-pyrazolyl borate complex which can be adopted as a component of catalytic systems used in the homo-, co-and ter-polymerization of a-olefins having general formula (I) wherein: R', R''and R'", the same or different, represent hydrogen, a linear or branched alkyl group having from 1 to 20 carbon atoms, or an aryl group with from 6 to 20 carbon atoms, optionally substituted with alkyl groups, both lin- ear and branched, aryl groups, halogen, carbonyl, amine or carboxyl groups; X is selected from halogens (fluorine, chlorine or bro- mine), carboxylates and 1, 3-dicarbonyl derivatives.

Examples of alkyl groups are methyl, ethyl, propyl, butyl, pentyl and isobutyl.

Examples of aryl groups are phenyl, naphthyl, anthra-

cenyl. Substituents of these groups are both linear and branched alkyls, aryls, halogen, carbonyls, amines or car- boxyls.

Examples of carboxylates are acetate, propionate, bu- tyrate, pentenoate, ethylhexenoate, both linear and branched, benzoates and naphthenates.

Typical examples of 1, 3-dicarbonyl compounds are 2,4- pentandione, 1, 1', 1l', 5, 5', 5''-hexafluoro-2, 4-pentandione, 1, 1', 1''-trifluoro-2, 4-pentandione, 1, 1', 1'', 5, 5', 5''-hexa- chloro-2,4-pentandione, 1, 1', 1"-trichloro-2, 4-pentandione.

In the preferred embodiment X is Cl.

Among the nickel complexes having general formula (I), those wherein R'is methyl, R''hydrogen and R''' is methyl (me), ter-butyl (t-Bu), 4-iso-propyl-phenyl or Cumyl (Cum), have proved to be particularly effective.

The present invention also relates to a process for the preparation of the complexes having general formula (I) which comprises the following steps: (a) treatment of a potassium or thallium tris (3,5- disubstituted) pyrazolyl borate with a derivative of nickel NiX2 selected from NiCl2, NiBr2, NiI2, Ni (CH3C) (O) CHC (O) CH3) 2, Ni (CF3C (O) CHC (O) CF3) 2, Ni (CH3C) (O) CHC (O) CF3) 2, Ni (CCl3C) (O) CHC (O) CH3) 2, Ni (CC13C) (O) CHC (O) CC13) 2, Ni (OCOCH3) 2, Ni (OCOCH2CH3) 2, Ni (OCOCH2CH2CH3) 2, Ni (OCOC6H5) 2 in an ether or alcohol sol-

vent, preferably methanol, tetrahydrofuran (THF) and 1,2- dimethoxyethane (DME); (b) separation, preferably by means of filtration, of the potassium or thallium salt formed in step (a); and finally (c) isolation of the nickel complex having formula (I).

Step (a) is carried out at a temperature ranging from - 78 to 200°C, preferably from 0 to 50°C. At these tempera- tures the duration of step (a) varies indicatively from 10 minutes to 150 hours. Reaction times ranging from 24 to 100 hours are usually used.

In the preferred embodiment, step (c) is carried out by evaporation of the solvent or precipitation of the com- plex by the addition of a suitable precipitating agent, usually a hydrocarbon solvent, preferably heptane.

A further objective of the present invention relates to a catalytic system for the homo-, co-and ter- polymerization of olefins comprising: (a) a nickel complex having general formula (I); and (b) a cocatalyst selected from organo-aluminum derivatives selected from aluminoxanes and compounds having general formula (II) AiRa wherein R is a C1-Czo alkyl group and al- kyl derivatives of magnesium having general formula (III) MgR2 wherein R is a C1-C20 alkyl group.

Typical examples of compounds having general formula (II) are AlMe3 (trimethylaluminum) AlEt3 (triethylalumi-

num), Al (i-Bu) 3 (triisobutylaluminum), Al (n-Oct) 3 (trioc- tylaluminum).

As far as aluminoxanes are concerned, it is known that these are compounds containing Al-O-Al bonds, with a varying O/Al ratio. These compounds can be obtained by the reaction, under controlled conditions, of an aluminum alkyl, or alumi- num alkyl halide, with water or other compounds containing pre-established quantities of available water, as, for exam- ple, in the case of the reaction of aluminum trimethyl with aluminum hexahydrate sulfate, copper pentahydrate sulfate or iron pentahydrate sulfate.

Aluminoxanes preferably used for the formation of the polymerization catalyst of the present invention are cyclic and/or linear, oligo-or polymeric compounds, characterized by the presence of repetitive units having the following for- mula (IV): wherein R15 is a C1-C6 alkyl group, preferably methyl. Each aluminoxane molecule preferably contains from 4 to 70 repeti- tive units which may also not all be the same, but contain different Rls groups.

Typical examples of cocatalysts having general formula .

(IV) are MAO, i-BuAlO, EtAlO. The preferred cocatalyst hav- ing general formula (IV) is methylaluminoxane (MAO) with a

weight average molecular weight (Mn) ranging from 400 to 2000.

Examples of compounds having general formula (III) are magnesium dimethyl, diethyl, dipropyl and dibutyl.

The molar ratio between the cocatalysts (b) and the nickel contained in the complex having formula (I) ranges from 1 to 1500, preferably from 1 to 1000, more preferably from 1 to 50.

The catalytic systems of the present invention can be used in the polymerization of a-olefins, preferably in the polymerization of a-olefins with from 3 to 10 carbon atoms and more preferably in the polymerization of ethylene, in the copolymerization of ethylene with propylene and higher a-olefins and in the terpolymerization of ethylene with propylene and dienes.

The copolymerization of ethylene-propylene to give EPR elastomeric copolymers and the terpolymerization of ethyl- ene-propylene-non-conjugated diene to give EP (D) M rubbers, are particularly preferred.

The diene can be selected from: - alicyclic dienes with a linear chain such as 1,4- hexadiene and 1,6-octadiene ; - acyclic dienes with a branched chain such as 5-methyl- 1,4-hexadiene, 7-methyl-1, 6-octadiene, 3, 7-dimethyl-1, 6- octadiene, 3, 7-dimethyl-1, 7-octadiene;

- alicyclic dienes with a single ring such as 1,4- cyclohexadiene, 1,5-cyclo-octadiene ; - dienes having condensed and bridged alicyclic rings such as methyltetrahydroindene, 5-ethylidene-2-norbornene (ENB), 5-propenyl-2-norbornene.

In the preferred embodiment, the diene is ENB or 7- methyl-1, 6-octadiene.

The elastomeric EPR and EP (D) M copolymers which can be obtained with the catalysts of the present invention con- tain from 10 to 40% in moles of propylene and quantities not higher than 2% of ENB.

The polymerization processes of a-olefins can be car- ried out in liquid phase (solution or suspension), at low (up to about 20 bars) or medium (from about 20 to about 50 bars) pressure and at temperatures ranging from 0 to 100°C.

In the preferred embodiment, the temperature ranges from 15 to 60°C and the pressure ranges from 1 to 10 bars.

The polymers and copolymers obtained with the process of the present invention can have a wide range of molecular weights. If the molecular weight is to be regulated to a value lower than the maximum value obtainable, it is possi- ble to use a chain transfer agent such as hydrogen, accord- ing to what is known in the art.

The weight average molecular weight of the polymer ob- tained in the presence of hydrogen varies from 50,000 to

500, 000.

Furthermore the elastomeric polymers obtained with the catalysts of the present invention have the advantage of the absence of colouring effects of the polymer both in transformation processes and storage.

The following examples are provided for a better un- derstanding of the present invention.

EXAMPLE 1 Synthesis of nickel chloride tris (3,5-dimethyl) pyrazolyl borate (Tp*NiCl) 0.065 g of anhydrous NiClZ (MW = 130 ; 0.5 mmoles) in 30 ml of methanol (MeOH) are placed in a 50 ml flask.

A suspension of 0.250 g of thallium tris (3,5- dimethyl) pyrazolyl borate TlTp* (MW = 501 ; 0.5 mmoles) in 20 ml of methanol are added to the green solution. After 24 hours at room temperature, the solution is evaporated, ethyl ether is then added and the mixture filtered. A light pink solid is obtained, which weighs 0.17 g (yield: 87%).

'H NMR (in CDC13, ppm) : 5.12 (3H, broad s), 1.24 (9H, s), 0.9 (9H, s); IR (in nujol): 2524 cm-1.

Ms = 391 m/z.

EXAMPLE 2 Synthesis of nickel chloride tris (3-methyl-5-t-butyl) pyra- zolyl borate Tpt-BUMeNiCl' 0.285 g of anhydrous NiCl2 (2.19 mmoles) in 60 ml of

anhydrous and degassed tetrahydrofuran (THF) are placed un- der argon in a 100 ml test-tube. 1 g of potassium tris (3- methyl-5-t-butyl) pyrazolyl borate KTpt-Bu,Me (2. 19 mmoles) is added to the yellow suspension. After 4 days at room tem- perature, the mixture is filtered, the solvent evaporated and a mixture of heptane-CH2Cl2 1/1 by volume, is added.

The purple crystals, analyzed by means of RX spectroscopy (Figure 1 and Tables 1-6), correspond to Tpt'Bu'MeNiCl and weigh 0.73 g (yield: 64. 4%).

1H NMR (in CDC13, ppm) : 5. 25 (3H, broad s), 2. 24 (27H, s), 1.3 (9H, s); IR (in nujol): 2558 cm-1.

EXAMPLE 3 Synthesis of nickel chloride tris [3-methyl-5- (4-iso- propylphenyl) ] -pyrazolyl borate Tp""eNiCl 0.100 g of anhydrous NiCl2 (0.77 mmoles) in 100 ml of anhydrous and degassed 1,2-dimethoxy ethane (DME) are placed under argon in a 150 ml test-tube. 0.5 g of potas- sium tris [3-methyl-5- (4-iso-propylphenyl)] pyrazolyl borate KTptmMe (O. 77 mmoles) are added to the yellow suspension.

When all the NiCl2 has dissolved, the solvent is evaporated and CH2Cl2 is added. The mixture is filtered and the meth- ylene chloride distilled, obtaining 480 mg of a green solid which is crystallized in heptane. The green crystals weight 0. 120 g (yield: 22%) and are characterized by means of RX spectroscopy (Figure 2 and Tables 7-12).

'H NMR (in CDC13, ppm): 7. 80 (6H, d), 7.15 (6H, d), 5.38 (3H, s), 2.43 (3H, q), 1.55 (9H, s); 1.02 (18H, d); IR (in nujol) : 2442 cm-1. mp = 180°-83°C. Ms = 702 m/z.

EXAMPLE 4 (comparative) 15.2 mg of Tp*NiCl (MW = 391; 3. 810-5 moles) in 100 ml of anhydrous and degassed toluene, are placed under argon in a 250 ml flask. 1.3 ml of methylaluminoxane (MAO), 1.5 M (50 equivalents of Al) are added to the pink solution. The purple solution is put under ethylene at a pressure of 1 bar and heated to 55°C for 2 hours. The solution quenched with 200 ml of methanol acidified with 10 ml of HC1 6 N is extracted with methylene chloride and produces 0.08 g of polyethylene polymer.

Activity: 2057 g PE/Ni mole EXAMPLE 5 5.2 mg of TpT-BU, MeNiCl (MW = 517; 1-10-5 moles) in 30 ml of anhydrous and degassed toluene, are placed under argon in a 100 ml flask. 0.5 ml of MAO 1.57 M (50 equivalents of Al) are added to the pink solution. The colourless solution is put under ethylene at a pressure of 1 bar and heated to 55°C for 2 hours.

The solution quenched with 200 ml of methanol acidi- fied with 10 ml of HC1 6 N is extracted with methylene chloride and produces 0.131 g of polyethylene polymer.

Activity: 13020 g PE/Ni mole.

EXAMPLE 6 5.2 mg of TpT-BU'MeNiCl (MW = 517; 1#10-5 moles) in 30 ml of anhydrous and degassed toluene, are placed under argon in a 250 ml flask. 6.36 ml of MAO 1.57 M (1000 equivalents of Al) are added to the pink solution. The colourless solu- tion is put under ethylene at a pressure of 1 bar and heated to 55°C for 2 hours.

The solution quenched with 200 ml of methanol acidi- fied with 10 ml of HCl 6 N is extracted with methylene chloride and produces 0.207 g of polyethylene polymer.

Activity: 20700 g PE/Ni mole EXAMPLE 7 10 mg of Tp'NiCI (MW = 704 ; 1. 42#10-5 moles) are placed under argon in a 100 ml flask. The complex is dis- solved in 20 ml of toluene. 0.5 ml of MAO 1.57 M (50 equivalents of Al) are added. The golden solution is put under ethylene at a pressure of 1 bar and maintained first at 55°C for 2 hours and subsequently at room temperature for 24 hours. The solution quenched with 200 ml of methanol acidified with 10 ml of HCl 6 N is extracted with methylene chloride and produces 0.25 g of polymer.

Activity: 17600 g PE/Ni mole.

EXAMPLE 8 7.04 mg of Tp"'""NiCl (MW = 704 ; 1#10-5 moles) are placed under argon in a 250 ml flask. The complex is dis-

solved in 80 ml of toluene. 6.5 ml of MAO 1.57 M (1000 equivalents of Al) are added. The solution becomes golden.

It is put under ethylene at a pressure of 1 bar and main- tained first at 55°C for 2 hours and subsequently at room temperature for 24 hours. The solution quenched with 200 ml of methanol acidified with 10 ml of HC1 6 N is extracted with methylene chloride and produces 0.24 g of polymer.

Activity: 23600 g PE/Ni mole.

EXAMPLE 9 10 mg of TpCum.MeNiCl (MW = 704 ; 1. 42-10-5 moles) are placed under argon in a 100 ml flask. The complex is dis- solved in 20 ml of toluene. 14 pl of magnesium dibutyl MgBu2 1 M in hexane (1 equivalent of Mg) are added. The so- lution is put under ethylene at a pressure of 1 bar and maintained at room temperature for 20 hours. The solution quenched with 200 ml of methanol acidified with 10 ml of HC1 6 N is extracted with methylene chloride and produces 0.05 g of polyethylene.

Activity: 3571 g PE/Ni mole.

EXAMPLE 10 5 mg of Tp'NiCI (MW = 704 ; 0. 7210-5 moles) are placed under argon in a 100 ml flask. The complex is dis- solved in 20 ml of toluene. 72 jul of MgBu2 1 M in hex- ane (10 equivalents of Mg) are added. The solution is put under ethylene at a pressure of 1 bar and maintained at

room temperature for 24 hours.

The solution quenched with 200 ml of methanol acidi- fied with 10 ml of HC1 6 N is extracted with methylene chloride and produces 0.04 g of polymer.

Activity: 5643 g PE/Ni mole.

EXAMPLE 11 5 mg of TpCum.MeNiCl (MW = 704 ; 0. 7210-5 moles) are placed under argon in a 100 ml flask. The complex is dis- solved in 20 ml of toluene. 1.4 ml of MgBu2 1 M (200 equivalents of Mg) are added. The solution is put under ethylene at a pressure of 1 bar and maintained at room tem- perature for 4 hours. The solution quenched with 200 ml of methanol acidified with 10 ml of HC1 6 N is extracted with methylene chloride and produces 0.10 g of polymer (PE).

Activity: 14080 g PE/Ni mole.

Description of the figures: Figure 1: ZORTEC plot which indicates the Tpt-Bu, Me NiCl structure. The hydrogens are omitted for the sake of clar- ity. Selected bond lengths (A) Ni-Nl (N3, N7) 1.995 (4); Ni- Cl 2.219 (3); N1-N2 1.335 (6); N2-B 1.358 (6). Selected bond angles (°) : N1-Ni-N3 (N7) 93.52 (18) ; ! Cl-Ni-Nl (N3, N7) 122. 74 (13).

Figure 2: ZORTEC plot which indicates the TptCum, Me NiCl structure. The hydrogens are omitted for the sake of clar- ity. Selected bond lengths (A) Ni-N5 2.020 (4); Ni-N3

2.029 (3); Ni-N7 2.102 (3); Ni-N1 2.157 (3); Ni-Cl 2.2911 (14).

Selected bond angles (°) : N5-Ni-N3 96.08 (15); N5-Ni-N7 89.37 (14) ; N3-Ni-N7 90.27 (14); N5-Ni-N1 92.43 (14); N3-Ni- N1 81.23 (13); N7-Ni-N1 171.45 (13); N5-Ni-Cl 117.56 (11); N3- Ni-Cl 146.35 (11); N7-Ni-Cl 90.77 (10); N1-Ni-Cl 95.80 (10).

Table 1: Crystallographic data and structural refinements for Tpt- Bu,MeNiCl Identification code Tpt-B", MeNiCl Empirical formula C24 H40 B1 C11 N6 Nil Molecular weight 517.60 Temperature 293 (2) Wave-length 0.71069 Å Crystalline system trigonal Spatial group R3 Cell unit dimensions a = 9.7160 (10) A alpha = 109.990 (10) deg. b = 9.7160 (10) A beta = 109. 990 (10) deg. c = 9.7160 (10) A gamma = 109.990 (10) deg.

Volume 692.16 (12) A3 z i Density (calculated) 1.242 Mg/m3 Absorption coefficient 0.820 mm-1 F (000) 276 Theta range for data collection 2.56 to 29.97 deg.

Refraction index 0 # h # 12, o # k # 12, #13 # 1 # 10 Reflections effected 1794 Independent reflections 1494 [R (int) = 0. 2387] Refinement method Full-matrix least-squares on F2 Data/restrictions/parameters 494/1/106 Goodness of fit on F2 1.016 Final R indexes I >2 [ (I)] = 0. 0667, wR2 = 0. 1781 R Indexes R1 = 0.0730, wR2 = 0. 1857 Absolute structure parameters 0.71 (4) Greatest base and peak diff. 1.231 and-0. 816 e. A-3

Table 2 Atomic co-ordinates (x 104) and parameters for the equiva- lent isotropic shifts (A x 103) for MeNiCl. U (eq) is defined as a third of the Uij orthogonalized tensor plot. x y z U (eq) Ni (1) 8 8 8 28 (1) Cl (1) 2352 (3) 2352 (3) 2352 (3) 53 (1) N (1)-1740 (6) -1741 (6) 86 (6) 31 (1) N (2) -3062 (6)-3067 (6)-1496 (6) 31 (1) B (1) -3107 (13)-3107 (13) -3107 (13) 33 (2) C (1) - 2032 (8) -2026 (8) 1250 (8) 38 (1) C (2)-3580 (10)-3579 (10) 357 (10) 48 (2) C (3)-4207 (8)-4203 (8)-1368 (8) 40 (1) C (4)-5793 (10) -5795 (10) -2842 (11) 59 (2) C (5)-826 (11)-826 (11) 3163 (8) 53 (2) C (6) 912 (12) -665 (13) 3695 (12) 64 (2) C (7) -677 (13) 901 (12) 3695 (11) 63 (2) C (8)-1580 (2)-1570 (2) 4056 (15) 103 (5)

Table 3 Selected bond lengths [Å] and angles for Tpt-BuMeNi Selected bond lengths (A) Ni-Nl (N3, N7) 1.995 (4); Ni-Cl 2.219 (3); N1-N2 1.335 (6); N2- B 1.358 (6).

Selected bond angles (°) : N1-Ni-N3 (N7) 93.52 (18); Cl-Ni-Nl (N3, N7) 122.74 (13).

Table 4 Bond lengths and angles for Tp5-Bu,MeNiCl Ni (1) - N (1) 1.995 (4) Ni (1) - N (1) #1 1.995 (4) Ni (1) - N (1) #2 1.995 (4) Ni (l)-Cl (l) 2.219 (3) N (1)-C (1) 1. 348 (7) N (1) -N (2) 1.355 (6) N (2) -C (3) 1.348 (7) N (2) -B (1) 1.538 (6) B (1)-N (2) &num 1 1.537 (6) B (1) -N (2) #2 1.538 (6) C (1) -C (2) 1.397 (10) C (1)-C (5) 1. 511 (9) C (2) -C (3) 1.379 (10) C (3) -C (4) 1.471 (10) C (5)-C (7) 1.514 (13) C (5)--C (6) 1.520 (12) C (5)-C (8) 1. 519 (11) N (l)-Ni (1) - N (1) #1 93.52 (18) N (l)-Ni (1) - N (1) &num 2 93.52 (18) N (1) #l-Ni (l)-N (1) #2 93.51 (18) N (l)-Ni (l)-Cl (l) 122. 74 (13) N (1) &num l-Ni (l)-Cl (l) 122.74 (13) N (1) #2-Ni (1) - Cl (1) 122.74 (13)

C (1) -N (1) -N (2) 107.9 (5) C (1)-N (1)-Ni (1) 139.4 (4) N (2)-N (1)-Ni (1) 112.7 (3) C (3)-N (2)-N (1) 110.2 (5) C (3) -N (2) -B (1) 129.4 (6) N (1) -N (2) -B (1) 120.4 (5) N (2) #1-B (1) -N (2) 108.6 (5) N (2) &num 1-B (1)-N (2) &num 2 108.6 (5) <BR> <BR> <BR> <BR> N (2)-3 (1) -N (2) &num 2 108.5 (5)<BR> <BR> <BR> <BR> N (1) -C (1)-C (2) 107.7 (5) N (1) -C (1) -C (5) 123.5 (5) C (2) -C (1) -C (5) 128.8 (6) C (3) -C (2)-C (1) 107. 3 (5) N (2) -C (3) -C (2) 106.9 (5) N (2) -C (3) -C (4) 124.4 (6) C (2) -C (3) -C (4) 128.7 (6) C (1) -C (5) -C (7) 110.1 (6) C (1) -C (5)-C (6) 110. 4 (7) C (7)-C (5)-C (6) 111.7 (7) C (1)-C (5)-C (8) 108.4 (8) C (7)-C (5)-C (8) 107.8 (9) C (6)-C (5)-C (8) 108.4 (9) Symmetry transformations used for generating equivalent at- oms: #1 zfxfy #2 y, z, x

Table 5 Anisotropic shift parameters (Å2 x 103) for Tpt-Bu, MeNiCl. The exponential anisotropic shift factors are: - 2 (2 h2 a*2 Ull +. + 2 h k a* b* U12] Ni (1) 24 (1) 24 (1) 24 (1) 9 (1) 9 (1) 9 (1) Cl (1) 38 (1) 38 (1) 38 (1) 5 (1) 5 (1) 5 (1) N (1) 29 (2) 30 (2) 25 (2) 12 (2) 12 (2) 10 (2) N (2) 25 (2) 25 (2) 28 (2) 10 (2) 10 (2) 6 (2) B (1) 30 (4) 30 (4) 30 (4) 12 (4) 12 (4) 12 (4) C (1) 38 (3) 37 (3) 34 (3) 19 (2) 20 (3) 15 (3) C (2) 48 (4) 47 (3) 45 (4) 28 (3) 27 (3) 15 (3) C (3) 32 (3) 34 (3) 41 (3) 17 (3) 17 (3) 9 (2) C (4) 39 (3) 43 (3) 54 (4) 18 (3) 18 (3) -2 (3) C (5) 53 (4) 55 (4) 25 (3) 18 (3) 17 (3) 11 (3) C (6) 56 (5) 67 (5) 55 (5) 35 (4) 16 (4) 29 (4) C (7) 65 (5) 61 (5) 48 (4) 16 (4) 31 (4) 30 (4) C (8) 98 (8) 119 (10) 54 (6) 50 (7) 44 (6) 11 (7)

Table 6 Co-ordinates of the hydrogen atoms (x 10') and isotropic shift parameters (Å2 x 103) for Tpt'Bu, MeNiCl. y z U (eq) H (l)-4142-4142-4142 60 (3) H (2) -4092-4097 836 60 (3) H (4A)-6475-5526-3560 140 (2) H (4B)-6427-6368-2439 140 (2) H (4C)-5511-6529-3486 140 (2) H (6A) 1456-86 3237 140 (2) H (6B) 762-1786 3261 140 (2) H (6C) 1616-19 4923 140 (2) H (7A) 51 1638 4917 140 (2) H (7B) -1793 754 3348 140 (2) H (7C)-194 1406 3156 140 (2) H (8A)-840-808 5274 140 (2) H (8B) -1670-2664 3751 140 (2) H (8C)-2591-1716 3706 140 (2)

Table 7 Crystallographic data and structural refinements for TpCum,MeNiCl Identification code TpCum,MeNiCl Empirical formula C52 H61 B Cl N6 Ni Molecular weight 903.06 Temperature 293 (2) K Wave-length 0. 71069 Å Crystalline system tricline Spatial group P-1 Cell unit dimensions a = 14.053 (2) A a = 90.67 (3) deg. b = 14.324 (6) A ß = 107.16 (5) deg. c = 14.395 (5) A y = 112.88 (2) deg.

Volume 2524.4 (14) Å3 z 2 Density (calculated) 1.188 Mg/m3 Absorption coefficient 0.479 nun-1 F (OOO) 958 Crystal dimensions 0.25 x 0.45 x 0.40 mm Theta range for data collection 2.50 to 23.00 deg.

Refraction index -15#h#14, -15#k#15, 0#1#15 Reflections effected 7342 Independent reflections 7013 [R (int) = 0. 0285] Refinement method Full-matrix least-squares on F2 Data/restrictions/parameters 7013/0/534 Goodness of fit on F2 1.036 Final R indexes [I>2 [(I)R] = 0. 0547, wR2 = 0.1388 R Indexes R1 = 0. 0950, wR2 = 0. 1582 Absolute structure parameters 0.71 (4) Greatest base and peak diff. 0.392 and-0.295 e. A-3.

Table 8 Atomic co-ordinates (x 104) and parameters for the equiva- lent isotropic shifts (A x 103) for TpCum,MeNiCl. U (eq) is defined as a third of the Uij orthogonalized tensor plot. x y z U (eq) Ni (l) 4018 (1) 2874 (1) 2386 (1) 46 (1) Cl (1) 5126 (1) 2934 (1) 1475 (1) 62 (1) B (1) 2252 (4) 3501 (4) 2614 (4) 55 (1) N (1) 3900 (3) 4298 (3) 2055 (3) 50 (1) N (2) 2921 (3) 4276 (3) 2075 (3) 51 (1) N (3) 3936 (3) 3343 (3) 3684 (3) 49 (1) N (4) 3033 (3) 3510 (3) 3630 (3) 50 (1) N (5) 2395 (3) 2058 (3) 1747 (3) SO (1) N (6) 1734 (3) 2432 (3) 2006 (3) 51 (1) N (7) 4149 (3) 1556 (3) 2922 (3) 51 (1) N (8) 4939 (3) 1305 (3) 2779 (3) 52 (1) CM 4361 (4) 5138 (3) 1666 (3) 53 (1) C (2) 3650 (4) 5619 (4) 1410 (4) 66 (1) C (3) 2760 (4) 5067 (4) 1673 (3) 60 (1) C (4) 1735 (5) 5214 (4) 1543 (4) 84 (2) C (6) 5684 (2) 5984 (2) 803 (2) 61 (1) C (7) 6727 (2) 6330 (2) 728 (2) 66 (1)

C (8) 7557 (2) 6202 (2) 1451 (2) 66 (1) C (9) 7345 (2) 5728 (2) 2249 (2) 64 (1) C (10) 6303 (2) 5381 (2) 2323 (2) 59 (1) C (5) 5472 (2) 5509 (2) 1600 (2) 52 (1) C (11) 8704 (4) 6518 (5) 1375 (5) 85 (2) C (12) 8949 (6) 7212 (6) 625 (6) 119 (2) C (13) 8930 (6) 5585 (6) 1225 (6) 117 (2) C (14) 452fol (4) 3493 (3) 4637 (3) 51 (1) C (15) 3974 (4) 3748 (4) 5194 (3) 62 (1) C (16) 3035 (4) 3738 (3) 4545 (3) 53 (1) C (17) 2137 (4) 3939 (4) 4726 (4) 73 (1) C (19) 5959 (3) 3204 (3) 5917 (2) 75 (1) C (20) 6926 (3) 3069 (3) 6232 (2) 93 (2) C (21) 7508 (2) 3114 (3) 5590 (3) 87 (2) C (22) 7123 (2) 3294 (3) 4634 (3) 78 (2) C (23) 6156 (2) 3430 (2) 4319 (2) 62 (1) C (18) 5574 (2) 3385 (2) 4961 (2) 55 (1) C (24) 8569 (6) 2962 (6) 5923 (7) 122 (3) C (25) 9452 (7) 3672 (10) 5736 (10) 267 (9) C (26) 8439 (8) 1964 (8) 5927 (12) 308 (10) C (27) 1756 (4) 1111 (3) 1280 (3) 54 (1) C (28) 690 (4) 878 (4) 1239 (4) 68 (1) C (29) 698 (4) 1716 (4) 1700 (4) 63 (1) C (30)-216 (4) 1920 (5) 1842 (5) 95 (2) C (32) 1904 (3)-551 (2) 1148 (3) 85 (2)

C (33) 2301 (3)-1193 (2) 815 (3) 98 (2) C (34) 2964 (3) -853 (3) 230 (3) 83 (2) C (35) 3229 (3) 129 (3)-22 (3) 83 (2) C (30) 2832 (3) 770 (2) 311 (3) 70 (1) C (31) 2170 (3) 431 (2) 896 (2) 59 (1) C (37) 3458 (6)-1537 (5)-97 (6) 108 (2) C (38) 2646 (6) -2505 (6) -697 (7) 154 (4) C (39) 4310 (6)-1633 (5) 735 (6) 115 (2) C (40) 5013 (4) 518 (3) 3259 (3) 57 (1) C (41) 4235 (4) 250 (4) 3724 (4) 68 (1) C (42) 3713 (4) 907 (3) 3496 (3) 58 (1) C (43) 2789 (4) 924 (4) 3800 (4) 77 (2) C (45) 6738 (3) 679 (2) 2982 (3) 100 (2) C (46) 7482 (3) 269 (3) 2963 (4) 122 (3) C (47) 7304 (3) -712 (3) 3192 (4) 100 (2) C (48) 6382 (4)-1283 (3) 3441 (4) 128 (3) C (49) 5638 (3) -873 (3) 3460 (4) 110 (2) C (44) 5816 (3) 108 (3) 3230 (3) 65 (1) C (50) 8120 (8) -1171 (9) 3190 (8) 162 (4) C (51) 8710 (9) -883 (8) 2577 (8)'197 (5) C (52) 8574 (8) -1430 (9) 4122 (8) 203 (6)

Table 9 Selected bond lengths [A] and angles [deg] for TpCum,MeNiCl Selected bond lengths (A) Ni-N5 2, 020 (4) ; Ni-N3 2, 029 (3) ; Ni-N7 2,102 (3); Ni-Nl 2, 157 (3); Ni-Cl 2, 2911 (14).

Selected bond angles (°) N5-Ni-N3 96,08 (15) ; N5-Ni-N7 89,37 (14); N3-Ni-N7 90,27 (14) ; N5-Ni-N1 92,43 (14) ; N3-Ni-N1 81,23 (13); N7-N1-N1 171, 45 (13); N5-Ni-C1 117, 56 (11); N3-Ni-Cl 146,35 (11); N7-Ni-Cl 90, 77 (10); N1-Ni-Cl 95,80 (10).

Table 10 Bond lengths and angles [deg] for TpCum,MeNiCl Ni(1) -N (5) 2.020 (4) Ni(1) -N (3) 2.029 (3) Ni (1)-N (7) 2.102 (3) Ni (1) -N(1) 2.157 (3) Ni (l)-Cl (1) 2. 2911 (14) B (1) -N (2) 1. 535 (6) B (1) -N (6) 1. 538 (6) B (1)-N (4) 1. 545 (6) N (1) -C (1) 1. 344 (5) N (1)-N (2) 1.374 (5) N (2) -C (3) 1. 344 (5) N (3)-C (14) 1.341 (5) N (3)-N (4) 1.361 (4) N (4) -C (16) 1. 351 (5) N (5)-C (27) 1. 332 (5) N (5)-N (6) 1.368 (4) N (6) -C (29) 1. 347 (5) N (7) -C (42) 1.341 (5) N (7)-N (8) 1.358 (5) N (8) -C (40) 1.350 (5) C (1)-C (2) 1. 389 (6)

C (1)-C (5) 1. 474 (5) C (2)-C (3) 1. 361 (6) C (3)-C (4) 1.493 (6) C (11)-C (12) 1. 499 (8) C(11) -C(13) 1.516 (9) C (14)-C (15) 1. 397 (6) C (14)-C (18) 1. 481 (5) C (15)-C (16) 1. 369 (6) C (16)-C (17) 1.489(6) C (21)-C (24) 1. 529 (7) C (24) -C (25) 1 367 (10) C (24)-C (26) 1.368(11) C (27) -C (28) 1.385 (6) C (27)-C (31) 1.487 (5) C (28)-C (29) 1.359 (7) C (29)-C (30) 1. 491 (7) C (34)-C (37) 1.542 (6) C (37)-C (38) 1. 459 (9) C (37)-C (39) 1.474 (9) C (40)-C (41) 1. 379 (6) C (40)-C (44) 1. 471 (5) C (4 (42) 1.392 (6) C (42) -C (43) 1.495 (6) C (47)-C (50) 1.528 (7) C (50)-C (51) 1.345 (10)

C (50)-C (52) 1.427 (11) N (5)-Ni (1)-N (3) 96. 08 (15) N (5)-Ni (1) -N (7) 89. 37 (14) N (3)-Ni (1) -N (7) 90.27 (14) N (5) -Ni (l)-N (1) 92. 43 (14) N (3)-Ni (1) -N (1) 81. 23 (13) N (7)-Ni (l)-N (1) 171. 45 (13) N (5)-Ni (1) -Cl (1) 117. 56 (11) N (3)-Ni (1) -Cl (l) 146.35 (11) N (7)-Ni (1) -Cl (1) 90.77 (10) N (1)-Ni (1) -Cl (1) 95.80 (10) N (2)-3 (1)-N (6) 108.7 (4) N (2)-B (1)-N (4) 108.2 (4) N (6)-3 (1)-N (4) 110.2 (4) C (1)-N (1) -N (2) 106.5 (3) C (l)-N (1) -Ni (1) 141.3 (3) N (2)-N (1)-Ni (1) 110.7 (2) C (3) -N (2)-N (1) 109.9 (3) C (3)-N (2) -B (1) 129.2 (4) N (1) -N (2)-B (1) 120.4 (3) C (14) -N (3)-N (4) 107.4 (3) C (14)-N (3) -Ni (1) 136.8 (3) N (4) -N (3)-Ni (1) 115. 7 (3) C (16)-N (4)-N (3) 109.8 (3) C (16)-N (4)-3 (1) 130.7 (4)

N (3) -N (4) -B (1) 119.3 (3) C (27)-N (5)-N (6) 106.6 (3) <BR> <BR> <BR> <BR> <BR> C (27)-N (5) -Ni (1) 135.5 (3) N (6)-N (5) -Ni (1) 116.0 (3) C (29) -N (6) -N (5) 109. 6 (3) C (29)-N (6)-B (1) i31. 3 (4) N (5)-N (6)-B (1) 119.0 (3) C (42) -N (7)-N (8) 106.2 (3) C (42) -N (7)-Ni (1) 135.7 (3) N (8) -N (7)-Ni (1) 117.6 (3) C (40)-N (8)-N (7) 111.1 (3) N (1)-C (1)-C (2) 108.7 (4) N (1)-C (1)-C (5) 124. 4 (4) C (2)-C (1)-C (5) 126.8 (4) C (3) -C (2)-C (1) 107.3 (4) N (2) -C (3) -C (2) 107.5 (4) N (2) -C (3) -C (4) 122.2 (4) C (2) -C (3)-C (4) 130.3 (4) C (7) -C (8) -C (11) 122. 0 (3) C (9) -C (8)-C (11) 117.9 (3) C (10) -C (5)-C (1) 120.6 (2) C (6)-C (5)-C (1) 119. 4 (2) C (12)-C (11)-C (13) 111.1 (6) C (12) -C (11) -C (8) 115.0 (5) C (13) -C (11)-C (8) 110.8 (5)

N (3) -C (14) -C (15) 108.6 (4) N (3) -C (14) -C (18) 121.7 (4) C (15)-C (14) -C (18) 129.7 (4) <BR> <BR> <BR> <BR> <BR> C (16) -C (15)-C (16) 106.7 (4) N (4) -C (16)-C (15) 107. 4 (4) <BR> <BR> <BR> <BR> <BR> N (4)-C (16) -C (7) 122. 4 (4) C (15)-C (lo')-C (17) 130.2 (4) C (22)-C (21)-C (24) 119. 4 (4) C (20)-C (21)-C (24) 120.6 (4) C (23) -C (18)-C (14) 121.2 (3) C (19) -C (18) -C (14) 118.8 (3) C (25) -C (24) -C (26) 120.2 (10) C (25) -C (24) -C (21) 117.1 (7) C (26)-C (24)-C (21) 115. 0 (7) N(5)-C(27)-C(28) 109.4(4) N(5)-C(27)-C(31) 123.4(4) C (28)-C (27) -C (31) 127.1 (4) C (29) -C (28) -C (27) 106.7 (4) N (6)-C (29)-C (28) 107. 6 (4) N (6)-C (29) -C (30) 121. 9 (4) C (28) -C (29)-C (30) 130.4 (5) C (35) -C (34) -C (37) 119.5 (4) C (33) -C (34) -C (37) 120.4 (4) C (36)-C (31)-C (27) 121.0 (3) C (32) -C (31) -C (27) 118. 9 (3)

C (38) -C (37) -C (39) 114. 7 (5) C (38)-C (37)-C (34) 113.9 (5) C (39)-C (37) -C (34) 111.4(6) N (8)-C (40)-C (41) 106. 6(4) N (8)-C (40)-C (44) 121. 7 (4) C (41)-C (40)-C (44) 131. 6 (4) C (40)-C (41)-C (42) 106.4 (4) N (7)-C (42)-C (41) 109.7 (4) N (7) -C (42)-C (43) 122. 4 (4) C (41)-C (42)-C (43) 127.9 (4) C (46) -C (45)-C (44) 120.0 C (45) -C (46)-C (47) 120.0 C (48)-C (47)-C (46) 120. 0 C (48)-C (47)-C(50) 119. 2 (5) C (46)-C (47)-C (50) 120.8 (5) C (47) -C (48) -C (49) 120.0 C (44) -C (49) -C (48) 120.0 C (49) -C (44)-C (45) 120.0 C (49)-C (44)-C (40) 118. 6. (3) C (45)-C (44)-C (40) 121.4 (3) C (51)-C (50)-C (52) 120.1 (8) C (51) -C (50)-C (47) 119.2 (7) C (52)-C (50)-C (47) 113.1 (7)

Table 11 Anisotropic shift parameters (Å2 x 103) for TpCum,MeNiCl. The exponential anisotropic shift factors are: - 2 (2 h2 a*2 Ull + + 2 h k a* b* U12 @ U11 U22 U33 U23 U13 U12 Ni (1) 47 (1) 46 (1) 51 (1) 12 (1) 18 (1) 24 (1) Cl (l) 77 (1) 63 (1) 69 (1) 26 (1) 41 (1) 40 (1) B (1) 56 (3) 56 (3) 66 (3) 13 (3) 26 (3) 32 (3) N (1) 54 (2) 47 (2) 56 (2) 14 (2) 21 (2) 26 (2) N (2) 53 (2) 43 (2) 0'1 (2) 12 (2) 18 (2) 29 (2) N (3) 50 (2) 49 (2) 53 (2) 11 (2) 20 (2) 24 (2) N (4) 51 (2) 49 (2) 55 (2) 8 (2) 22 (2) 24 (2) N (5) 47 (2) 50 (2) 56 (2) 5 (2) 15 (2) 24 (2) N (6) 43 (2) 55 (2) 53 (2) 9 (2) 16 (2) 25 (2) N (7) 52 (2) 52 (2) 58 (2) 14 (2) 21 (2) 26 (2) N (8) 56 (2) 51 (2) 62 (2) 18 (2) 22 (2) 32 (2) (1) 62 (3) 47 (3) 53 (3) 13 (2) 18 (2) 27 (2) C (2) 79 (3) 53 (3) 78 (3) 25 (3) 31 (3) 36 (3) C (3) 70 (3) 58 (3) 64 (3) 16 (2) 20 (3) 40 (3) C (4) 94 (4) 90 (4) 104 (4) 37 (3) 40 (3) 67 (4) C (6) 64 (3) 54 (3) 58 (3) 19 (2) 15 (2) 22 (2) C (7) 70 (3) 62 (3) 62 (3) 20 (2) 26 (3) 18 (3) C (8) 61 (3) 62 (3) 66 (3) 9 (3) 20 (3) 15 (2) C (9) 58 (3) 66 (3) 61 (3) 17 (2) 11 (2) 22 (2)

C (10) 65 (3) 52 (3) 54 (3) 14 (2) 15 (2) 20 (2) C (5) 58 (3) 44 (2) 54 (3) 12 (2) 15 (2) 21 (2) C (11) 70 (4) 97 (4) 88 (4) 16 (3) 32 (3) 29 (3) C (12) 99 (5) 125 (6) 135(6) 40 (5) 66 (5) 26 (4) C (13) 101 (5) 140 (6) 131 (5) 24 (5) 54 (5) 60 (5) C (14) 60 (3) 41 (2) 47 (3) 7 (2) 14 (2) 17 (2) C (15) 78 (3) 61 (3) 49 (3) 9 (2) 20 (3) 30 (3) C (16) 64 (3) 47 (3) 57 (3) 9 (2) 28 (2) 26 (2) C (17) 85 (4) 80 (4) 72 (3) 7 (3) 37 (3) 41 (3) C (19) 74 (4) 81 (4) 64 (3) 21 (3) 14 (3) 32 (3) C (20) 85 (4) 109 (5) 74 (4) 33 (3) 8 (3) 43 (4) C (21) 73 (4) 68 (4) 96 (5) 14 (3)-5 (3) 30 (3) C (22) 59 (3) 76 (4) 95 (4) 7 (3) 18 (3) 31 (3) C (23) 52 (3) 65 (3) 62 (3) 6 (2) 10 (2) 22 (2) C (18) 56 (3.) 45 (2) 53 (3) 5 (2) 7 (2) 19 (2) C (24) 81 (5) 122 (6) 157 (7) 36 (5) 6 (5) 59 (5) C (25) 79 (6) 362 (18) 379 (19) 238 (16) 71 (9) 108 (9) C (26) 102 (7) 137 (9) 630 (3) 26 (13)-1 (12) 80 (7) C (27) 50 (3) 53 (3) 55 (3) 5 (2) 14 (2) 19 (2) C (28) 54 (3) 58 (3) 81 (4)-3 (3) 19 (3) 14 (2) C (29) 46 (3) 71 (3) 70 (3) 8 (3) 19 (2) 24 (3) C (30) 54 (3) 91 (4) 136-8 (4) 35 (3) 24 (3) C (32) 88 (4) 55 (3) 115 (5) 9 (3) 44 (4) 26 (3) C (33) 118 (5) 50 (3) 133 (5) 7 (3) 47 (4) 39 (3) C (34) 72 (4) 80 (4) 96 (4)-9 (3) 21 (3) 35 (3)

C (35) 82 (4) 70 (4) 107 (5) 2 (3) 42 (3) 32 (3) C (36) 73 (3) 56 (3) 84 (4) 1 (3) 30 (3) 27 (3) C (31) 53 (3) 50 (3) 67 (3)-4 (2) 12 (2) 20 (2) C (37) 100 (5) 87 (5) 149 (6)-7 (4) 32 (5) 59 (4) C (38) 108 (6) 119 (6) 233 (10)-72 (6) 31 (6) 63 (5) C (39) 110 (5) 97 (5) 164 (7) 21 (5) 48 (5) 64 (4) C (40) 60 (3) 58 (3) 61 (3) 19 (2) 19 (2) 33 (2) C (41) 78 (3) 68 (3) 81 (4) 36 (3) 36 (3) 42 (3) C (42) 60 (3) 56 (3) 69 (3) 24 (2) 30 (2) 28 (2) C (43) 79 (4) 79 (4) 100 (4) 42 (3) 56 (3) 40 (3) C (45) 93 (4) 89 (4) 159 (6) 51 (4) 71 (4) 55 (4) C (46) 105 (5) 117 (6) 202 (8) 69 (6) 97 (6) 70 (5) C (47) 127 (6) 129 (6) 108 (5) 60 (4) 61 (4) 98 (5) C (48) 152 (7) 131 (6) 200 (8) 106 (6) 118 (6) 113 (6) C (49) 121 (5) 105 (5) 174 (7) 92 (5) 93 (5) 84 (4) C (44) 70 (3) 75 (3) 67 (3) 29 (3) 26 (3) 45 (3) C (50) 180 (8) 249 (11) 197 (9) 131 (9) 128 (8) 178 (9) C (51) 269 (13) 244 (12) 242 (12) 115 (10) 164 (11) 212 (11) C (52) 211 (11) 300 (14) 250 (13) 159 (11) 132 (10) 216 (11)

Table 12 Co-ordinates of the hydrogen atoms (x 104) and isotropic shift parameters (Å2 x 103) for TpCum,MeNiCl. x y z U (eq) H (1) 1679 3690 2695 105 (7) H (2) 3763 6209 1114 105 (7) H (4A) 1638 5274 2170 170 (6) H (43) 1123 4636 1119 170 (6) H (4C) 1784 5825 1256 170 (6) H (6) 5129 6069 319 73 H (7) 6869 6648 194 80 H (9) 7900 5642 2732 77 H (10) 6161 5064 2857 71 H (11) 9220 6903 2014 105 (7) H (12A) 8795 7793 734 170 (6) H (123) 8503 6846-21 170 (6) H (12C) 9705 7439 683 170 (6) H (13A) 9648 5799 1173 170 (6) H (13B) 8399 5151 633 170 (6) H (13C) 8886 5215 1773 170 (6) H (15) 4202 3895 5875 105 (7) H (17A) 2309 4120 5418 170 (6) H (17B) 1467 3336 4486 170 (6) H (17C) 2056 4493 4390 170 (6)

H (19) 5570 3174 6347 90 H (20) 7183 2948 6872 ill H (22) 7512 3325 4204 93 H (23) 5899 3551 3680 75 H (24) 8787 3171 6631 105 (7) H (25A) 9482 4344 5864 170 (6) H (25B) 9386 3534 5061 170 (6) H (25C) 10108 3637 6152 170 (6) H (26A) 9126 1943 6275 170 (6) H (26B) 8186 1634 5263 170 (6) H (26C) 7914 1616 6244 170 (6) H (28) 85 267 952 105 (7) H (30A)-101 2041 2532 170 (6) H (30B) -894 1338 1537 170 (6) H (30C)-243 2511 1548 170 (6) H (32) 1461-778 1539 101 H (33) 2124-1850 984 117 H (35) 3672 356-413 100 H (36) 3010 1427 142 84 H (37) 3843-1157-532 105 (7) H (38A) 3008-2906-844 170 (6) H (38B) 2228-2371-1298 170 (6) H (38C) 2167-2874-344 170 (6) H (39A) 4855-964 170 (0') H (39B) 4642-2016 500 170 (6)

H (39C) 3987-1983 1203 170 (6) H (41) 4089-268 4113 105 (7) H (43A) 2853 722 4441 170 (6) H (43B) 2109 457 3338 170 (6) H (43C) 2814 1603 3816 170(6) H (45) 6857 1335 2828 120 H (46) 8099 651 2796 146 H (48) 6263-1939 3595 153 H (49) 5021 -1255 3626 131 H (50) 7607-1858 2847 105 (7) H (51A) 9290-216 2836 170 (6) <BR> <BR> H (SlB) 8247-860 1943 170 (6) H (51C) 9014-1366 2513 170 (6) H (52A) 8972-1825 4050 170 (6) H (52B) 7997-1825 4369 170 (6) H (52C) 9059-815 4574 170 (6) Table 13 Polymerization tests catalyzed by Nickel chloride tris- (3,5-disubstituted) pyrazolyl borates Ex. Catalyst Cocatalyst [Cocat]/ [Cat] Solvent T t Activity (µmoles) molar ratio (ml) (°C) (hours) g PE/mole Ni 4 Tp*NiCI MAO 50 100 55 2 2057 (38) 5 Tpt-Bu,MeNiCl MAO 50 30 55 2 13060 (10) 6 Tpt-Bu,MeNiCl MAO 1000 30 55 2 20700 (10) 7 TpCum,MeNiCl MAO 50 20 55 2 17600 (14) 8 TpCum. MeNiCl MAO 1000 80 55 2 23600 (10) TpCum,MeNiCl MgBu2 1 20 25 20 3571 (14) TpCum,MeNiCl MgBu2 10 20 25 24 5643 (70) 11 TpCum,MeNiCl MgBu2 200 20 25 4 14080 (71)

COMMENTS ON TABLE 13: All the various complexes when treated with MAO proved to be active in the polymerization of ethylene (Ex. 4-5 and 7). Even though an increase in the MAO/catalyst ratio causes an increase in the yield to polymer, the latter is also acceptable at a low ratio value such as 50 (Example 8 vs. 7).

The yield to polymer greatly depends on the group situated in position 3 of the pyrazole residue Me<t-Bu<Cum (Ex. 4-5 and 7). The activity in fact increases by nine times passing from methyl to cumyl (Example 4 vs. 7). Acti- vators such as dibutylmagnesium are also effective as co- catalysts (Examples 9-11) even if higher cocata- lyst/catalyst molar ratios are required for reaching ac- tivities comparable to those obtained with much lower ra- tios with MAO (Example 11 vs. 7).