Trimethylsilylcyclopentadienylchromium(III) complexes with diphenyl-2-pyridylphosphine: synthesis, structural characterisation and catalytic behaviour of [(C6H5)2PC5H4NH][(η5-Me3SiCp)CrCl3]

Reaction of CrCl3 with LiCpSiMe3 in THF leads to the formation of a solvated intermediate, [(η5-Me3SiCp)CrCl2(THF)], which in turn reacts with diphenyl-2-pyridylphosphine to yield the complex [(C6H5)2PC5H4NH][(η5-Me3SiCp)CrCl3] (1) in 66% yield. As a secondary product was isolated the neutral complex [(η5-Me3SiCp)CrCl2{(C6H5)2PC5H4N}] (2) in 5% yield. The structure of complex 1 has been determined by single crystal X-ray diffraction. In the anion the metal centre shows a pseudo-octahedral geometry with the centroid of the trimethylsilylcyclopentadienyl ligand occupying the centre of three octahedral sites, and three chloride atoms completing the co-ordination sphere. Complex 1 in the presence of MAO leads to the formation of an active catalyst for the polymerization of ethylene.