Titanium-Catalyzed Dehydrocoupling of Silanes: Direct Conversion of Primary Monosilanes to Titanium(0) Oligosilane Complexes with Agostic α-Si-H···Ti Interactions

The reaction of TiMe2(dmpe)2 with excess PhSiH3 affords methane, PhSiMeH2, and the titanium trisilane complex Ti(Si3H5Ph3)(dmpe)2 (1), which slowly reacts with an additional molecule of PhSiH3 to give the tetrasilane complex Ti(Si4H6Ph4)(dmpe)2 (2). These molecules contain metal-bound oligosilane ligands formed by the dehydrocoupling of PhSiH3; 1 contains the linear trisilane PhSiH(SiH2Ph)2, and 2 contains the branched tetrasilane PhSi(SiH2Ph)3. An X-ray crystallographic study of 2 shows that the titanium centers adopt distorted octahedral geometries in which the two dmpe groups and the oligosilane molecule act as bidentate ligands. Two of the SiPhH2 groups in the silane ligand are involved in agostic Ti···H−Si interactions with the titanium center.