Unexpected Formation of Polydentate Phosphinoalkyl−Silyl and −Germyl Ligands from Reaction of [MoH₄(Ph₂PCH₂CH₂PPh₂)₂] with Organosilanes and Organogermanes:  Novel Activation of Mo−H, E−H (E = Si, Ge), and C−H Bonds in the Same System

Abstract

Reaction of [MoH 4 (Ph 2 PCH 2 CH 2 PPh 2 ) 2 ] ( 1 ) with PhEH 3 (E = Si, Ge) in refluxing toluene yielded the novel complexes [MoH 3 {[Ph 2 PCH 2 CH 2 P(Ph)C 6 H 4 - o ] 2 (Ph)E- P,P,P,P,E }] (E = Si ( 2 ), Ge ( 3 )) with a quinquidentate ligand comprised of a P−P−E−P−P framework as a result of the oxidative addition involving E−H bond cleavage with concomitant selective activation of the ortho C−H bonds of the two dppe ligands. When secondary Ph 2 SiH 2 was employed in a similar reaction with 1, a trihydrido complex with a tridentate ligand ([Ph 2 PCH 2 CH 2 P(Ph)C 6 H 4 - o ]Ph 2 Si- P,P,Si ) comprised of a P−P−Si framework was isolated. On the other hand, the reaction between Ph 2 GeH 2 and 1 proceeded with accompanying evolution of 1 mol of benzene to give 3; that is, in addition to the Ge−H and C−H activation, Ge−C(Ph) bond cleavage took place. It is concluded that the reaction path includes the intermediacy of silylene or germylene metal complexes via an α-migration process on the basis of deuterium-labeling studies.