EFFICIENT HOMOGENEOUS HYDROSILYLATION OF OLEFINS BY USE OF COMPLEXES OF PT-0 WITH SELECTED ELECTRON-DEFICIENT OLEFINS AS LIGANDS

A family of complexes of general formula [Pt(eta(2)-Ol(E)){(eta(4)-CH2 =CHSiMe2)(2)O}], where Ol(E) is a di-, tri- or tetrasubstituted electr on-deficient olefin such as fumaronitrile, diethylfumarate, tetracyano ethylene, ethylenetetracarboxylate, a naphthoquinone or dihydronaphtho quinone, were synthesised from the Karstedt catalyst solution containi ng [Pt-2(CH2=CHSiMe2)(2)O)(3)] (1). The structures of these complexes were examined by H-1, C-13 and Pt-195 NR IR spectroscopy. The X-ray cr ystallographic structure of [Pt(eta(2)-MeNQ){(eta(4)-CH2=CHSiMe2)(2)O} ] (MeNQ = methylnaphthoquinone) was determined; the MeNQ ligand is bou nd to Pt by a eta(2)-olefin interaction. Certain of these complexes, p articularly the naphthoquinone and dihydronaphthoquinone derivatives, were found to catalyse very efficiently the hydrosilylation of a varie ty of olefins. Tests in the presence of Hg, dibenzo[a, e]cyclooctatetr aene or molecular oxygen indicated that the catalytic process was homo geneous in nature. The addition of excess Ol(E) to the catalyst soluti ons greatly extended the lifetime and productivity of these catalysts, which were more efficient both in rate and overall product yield than the original Karstedt catalyst solution. Spectroscopic studies lead u s to propose that the stabilising ligand Ol(E) remains bound to Pt thr oughout the catalytic cycle; this results in increased stability and h igh catalytic activity.