Phosphine compounds are typically used as ligands in metal-based homogeneous catalysts, with such catalysts being used in hydroformylation and/or hydrogenation processes. Thus, in the case of hydroformylation processes for the production of oxygenated products, particularly aldehydes and/or alcohols, olefinic feedstocks are reacted with carbon monoxide and hydrogen at elevated temperatures and pressures in the presence of such catalysts.

Examples of such phosphine compounds are aryl phosphine and alkyl phosphine compounds used as ligands in rhodium and/or cobalt-based homogeneous catalysts in hydroformylation and/or hydrogenation processes. Specific examples of such compounds are trialkyl phosphines and bicyclic tertiary phosphines such as 9-phosphabicyclo [3.3. 1] nonane and 9-phosphabicyclo [4.2. 1] nonane represented by formulas (I) and (II) respectively : I n

The compounds or ligands I and 11 are available commercially, as a mixture, and are referred to in the art under the collective chemical name eicosyl phoban. For example, U. S. Pat No. 3,400, 163, U. S. Pat. No.

3,420, 898 and U. S. Pat. No. 3,501, 515 describe or refer to eicosyl phoban.

Thus, according to a first aspect of the invention, there is provided a bicyclic tertiary phosphine compound having two cyclic structures and a ligating phosphorus atom, with the ligating phosphorus atom forming part of the largest ring structure of the molecule, and with fewer than two hydrocarbon substituents being present on the carbon atoms of the cyclic structures of the molecule.

The compound may be a [3.3. 1] phosphabicyclononane represented by formula (III) : III where R1 is an alkyl, branched alkyl, cycloalkyl, or aryl group.

Instead, the compound may be a [3.2.2]phosphabicyclononane represented by formula (IV):

IV where R, is an alkyl, branched alkyl, cycloalkyl, or aryl group.

In one embodiment of the invention, Ri of the phosphabicyclononane of formulae (III) and (IV) may be a linear C2 to C20 hydrocarbon chain.

The family of ligands of formulas (III) and (IV) is named VCH (as these ligands are vinylcyclohexene derived); thus, each ligand can be denoted 'VCH', together with a suffix corresponding to the carbon number of Ri. For example, in one embodiment of the invention, the ligand may be VCH- C12. Thus, VCH-C12 will be represented by the formulas V and VI, where Ri is C, 2H25.

V vi However, in other embodiments of the invention, Ri of the phosphabicyclononane of formulae III and IV may be a cycloalkyl, an aryl or a branched alkyl group. Thus, when R, is a cycloalkyl group, it may be cyclohexyl; and when Ri is an aryl group, it may be a phenyl.

The bicyclic tertiary phosphine compound according to the first aspect of the invention is suitable for use as a ligand in a metal-based homogeneous catalyst, typically a metal-based homogeneous hydroformylation or hydrogenation catalyst.

Thus, according to a second aspect of the invention, there is provided a ligand composition for a metal-based homogeneous catalyst, the ligand composition including a bicyclic tertiary phosphine compound having two cyclic structures and a ligating phosphorus atom, with the ligating phosphorus atom forming part of the largest ring structure of the molecule, and with fewer than two hydrocarbon substituents being present on the carbon atoms of the cyclic structures of the molecule.

In particular, the bicyclic tertiary phosphine compound may be a [3. 3. 1] phosphabicyclononane represented by formula (III), as hereinbefore defined.

Instead, the ligand composition may comprise a plurality of the bicyclic tertiary phosphine compounds in the form of a mixture of bicyclic tertiary phosphine isomers. Thus, the ligand composition may comprise a mixture of isomers of the bicyclic tertiary phosphine of formula (ici). An example of such an isomer is [3.2. 2] phosphabicyclononane represented by formula (IV), as hereinbefore described.

Thus, the ligand composition may comprise a mixture of [3.3. 1] phosphabicyclononane of formula (III) and [3.2. 2] phosphabicyclononane of formula (IV).

According to a third aspect of the invention, there is provided a method of preparing a bicyclic tertiary phosphine compound, which method includes

reacting a hydrocarbylphosphine with a mono-or un-substituted vinylcyclohexene, thereby forming a bicyclic tertiary phosphine compound having two cyclic structures and a ligating phosphorus atom, with the ligating phosphorus atom forming part of the largest ring structure of the molecule, and with fewer than two hydrocarbon substituents being present on the carbon atoms of the cyclic structures of the molecule.

The hydrocarbylphosphine may be of the general formula R-PH2, wherein R is an alkyl, a branched alkyl, cycloalkyl, or an aryl radical to which the phosphorous atom is linked by means of a primary, secondary or tertiary carbon atom. According to a specific embodiment of this aspect of the invention, the hydrocarbylphosphine may be dodecylphosphine, with the bicyclic tertiary phosphine compound that is produced then being 2- dodecyl-2-phosphabicyclo [3. 3. 1] nonane, ie a phosphabicyclononane compound in accordance with formula (V) hereinbefore described.

The reaction or synthesis of the hydrocarbylphosphine with the vinylcyclohexene may be carried out in the presence of a catalyst. The catalyst may be a free radical initiator.

More particularly, the method may then include mixing the hydrocarbylphosphine and the vinylcyclohexene with a precursor of the free radical initiator to produce a reaction mixture, and forming the free radical initiator in situ in the reaction mixture.

The free radical initiator precursor may be a nitrile compound. More particularly, the free radical initiator precursor may be an azo bis isovaleronitrile. Azo bis isovaleronitriles are also known by the designation VAZO. Thus, for example, the free radical initiator precursor may be 1,2-azo bis isovaleronitrile, which has a 10 hour halflife at 67°C.

Thus, 1,2-azo bis isovaleronitrile is also known as VAZ067.

The formation of the free radical initiator may be effected by decomposing the precursor.

In one embodiment of the invention, the decomposition of the precursor may be effected thermally. Thus, the reaction or synthesis may then be carried out at an elevated reaction temperature, which may be in the temperature range from 25°C and 110°C. The synthesis may then more specifically be carried out at a reaction temperature in the temperature range from 40°C to 90°C. Thus, when the initiator or catalyst is 1,2-azo bis isovaleronitrile, the synthesis may be carried out at a reaction temperature of about 80°C, at which temperature the 1,2-azo bis isovaleronitrile will be thermally decomposed into free radicals which act as an initiator or catalyst for the reaction of the hydrocarbylphosphine with the vinylcyclohexene..

However, another azo bis isovaleronitrile may instead be used, eg an azo bis isovaleronitrile that thermally decomposes at a lower temperature than 1,2-azo bis isovaleronitrile, such as VAZ052 which has a 10 hour halflife at 52°C. Thus, when VAZO initiators are used that are less thermally stable than VAZ067, the synthesis may be effected at lower temperatures. For example, when VAZ052 is used, the synthesis may be carried out at a reaction temperature which is as low as 35°C.

In another embodiment of the invention, the decomposition of the precursor may be effected photochemically. In particular, the reaction mixture may then be subjected to UV radiation, which decomposes the initiator at low temperatures and thereby initiates the reaction of the hydrocarbylphosphine with the vinylcyclohexene.

The reaction or synthesis may be carried out in the presence of a solvent.

The solvent may be an organic solvent, and in particular may be an aromatic organic solvent. For example, the solvent may be toluene.

The bicyclic tertiary phosphine compound according to the first aspect of the invention is thus suitable for use as a ligand in a metal-based homogeneous catalyst, typically a metal-based homogeneous hydroformylation or hydrogenation catalyst.

The invention will now be described in more detail, with reference to the following non-limiting example.

EXAMPLE 1 Synthesis of 2-dodecyl-2-shosshabicvclo [3. 3. 1] nonane A stirred inerted reactor was charged with 442 g (2.19 moles) of dodecylphosphine. A solution containing 35 g (0.182 moles) of 1,2-azo bis isovaleronitrile (VAZ068) in 235 g (2.17 moles) of 4-vinylcyclohexene and 133 g of toluene was added to the dodecylphosphine, and the resultant reaction mixture maintained under stirring, for a 24 hour period, at 70°C. The ratio of desired product: unconverted dodecylphosphine : intermediate: by-product, in the resultant mixture, was 56.0 : 2.5 : 3.8 : 9.9.

This product mixture was then heated under 2mm Hg (0.27kPa) pressure at 200 C to remove the unconverted dodecylphosphine and other volatile impurities. The recovered product contained 85% 2-docecyl-2- phosphabicyclo [3. 3. 1] nonane.

An improvement to the yield of the desired product can be accomplished by adding the 4-vinylcyclohexene slowly to at least a 100 fold molar excess of dodecylphosphine containing the radical initiator. The excess dodecylphosphine is recoverable by vacuum distillation from the higher

boiling product. Dodecylphosphine has a vapour temperature of 94°C at 2mm Hg pressure.

EXAMPLE 2 Synthesis of 2-cvclohexvl-2-phosphabicvclo [3. 3. 1] nonane A stirred inerted reactor was charged with 17 g (0.15 moles) of cyclohexylphosphine. A solution containing 3.5 g (0.018 moles) of 1,2- azo bis isovaleronitrile (VAZ068) in 17.3 g (0.16 moles) of 4- vinylcyclohexene and 133 g of toluene was added to the cyclohexylphosphine, and the resultant reaction mixture maintained under stirring, for a 78 hour period, at 90°C. The ratio of desired product: unconverted cyclohexylphosphine : intermediate: by-product, in the resultant mixture, was 83: 0: 3.8 : 13.2. This product mixture was then heated under 2mm Hg (0.27kPa) pressure at 200 C to remove the unconverted cyclohexylphosphine and other volatile impurities. The recovered product afforded a 55% yield of 2-cyclohexyl-2- phosphabicyclo [3.3. 1] nonane.

EXAMPLE 3 Synthesis of 2-phenyl-2-phosphabicvclo [3. 3. 1] nonane A stirred inerted reactor was charged with 9.5 g (0.086 moles) of phenylphosphine. A saturated solution of 1,1-azo bis cyclohexanecarbonitrile (VAZO@) in toluene (10 ml) containing in 9.3 g (0.086 moles) of 4-vinylcyclohexene was added to the phenylphosphine, and the resultant reaction mixture maintained under stirring, for a 78 hour period, at 88°C. 31P NMR indicated 83% of the desired tertiary phosphine product with 4 % of the secondary phosphine remaining. This product mixture was then heated under 2mm Hg (0.27kPa) pressure at 200 C to remove the unconverted phenylphosphine and other volatile impurities. The recovered product product afforded a 36% yield of 2- phenyl-2-phosphabicyclo [3. 3. 1] nonane.