TRIMETHYLSILYLCYCLOOCTADIENE-TRANSITION METAL-COMPLEXES - METAL-CATALYZED PROTODESILYLATION OF CYCLIC VINYLSILANES, AND TRANSFER HYDROGENATION PROMOTED BY THE DISPLACED SILYL GROUP

Complexes of 1-trimethylsilyl-1,5-cyclooctadiene (TMS-COD, 2) with Ag(I), Rh(I), Pd(II) and Pt(II) have been prepared and characterised. The distortion in their structures in comparison with the near symmetrical structures of the corresponding 1,5-cyclooctadiene (COD, 1) complexes, which is obviously attributable to the presence of vinylic SiMe3 group, is clearly indicated by their H-1 and C-13 NMR spectral characteristics. The silver complex is somewhat unstable, but the other complexes are quite stable. An unstable Cu(I) complex that could not be satisfactorily characterised was also obtained. If appropriate conditions for the preparation of Rh and Pd complexes are not maintained, desilylation occurs, accompanied by reduction of COD to cyclooctene by transfer of hydrogen from the solvent alcohol. The displaced silicon containing moiety seems to enhance the transfer hydrogenation. Attempts to prepare Ru(II) complex resulted in the formation of a complex of desilylated diene (Ru(II)-COD).