The use of platinum complexes as catalysts for allylic substitution has been studied. A variety of different complexes catalyse the reaction, and several substrates have been tested. In the alkylation of mono(alkyl)-substituted allylic acetates, regioselectivity is highly dependent on ligand choice. By using tricyclohexylphosphine as the ligand, almost complete formation of branched products is observed. The development of a highly enantioselective (ca. 80-90% ee) reaction that makes use of chiral diphenylphosphinooxazoline ligands (abbreviated as (S)-PN) is also described. The enantioselectivity is highly dependent on the ratio of ligand to platinum (when the ratio ligand/Pt is greater than 1:1, the ee drops off dramatically). This is in contrast to palladium and is interpreted in terms of differing coordination chemistry for the two metals ((S)-PN is hemilabile when complexed to platinum) and should be of significance to future systems that utilise heterobidentate ligands. The crystal structures of two isoelectronic platinum and palladium complexes [[(S)-PN]MCl2] are also described.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

[GRAPHICS]Tricyclohexylphosphine, Cy3P, in conjuction with [(C3H5)PdCl](2) catalyzes allylic alkylation of terminal allylic acetates with high regioselectivity toward branched products, which is in contrast to most other palladium catalysts. Other ligands, even those of similar basicity or bulkiness, did not show the same regioselectivity. Alkylation of 1,4-diacetoxy-2-butene gave predominantly branched products which had not been observed previously.

Novel organoplatinum complexes of the enantiomerically pure P, N ligand, (4S)-2-(2-(diphenylphosphino)phenyl)-4-isopropyl-1,3-oxazoline, have been synthesized and shown to act as Lewis acids. These complexes consist of the bidentate P, N ligand, an achiral organic ligand, and a solvent ligand that can be readily displaced by organic substrates. The solvent ligand is situated cis to the nitrogen donor and, as such, is in a "chiral pocket" created by the oxazoline ring. The complexes are readily prepared from the well-known, and versatile, precursors (COD)PtR2 and are obtained as single isomers. Two of the complexes have had their structures elucidated by X-ray crystallography, The cationic complexes were shown to be enantioselective catalysts in the Michael reaction of alpha-cyano carboxylates with methyl vinyl ketone.

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Platinum complexes derived from phosphino-oxazolines are highly enantioselective catalysts for allylic alkylation reactions, but show different behaviour from related palladium complexes.