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 [MoH4(Ph2PCH2CH2PPh2)2] (1) with PhEH3 (E = Si, Ge) in refluxing toluene yielded the novel complexes [MoH3{[Ph2PCH2CH2P(Ph)C6H4-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 Ph2SiH2 was employed in a similar reaction with 1, a trihydrido complex with a tridentate ligand ([Ph2PCH2CH2P(Ph)C6H4-o]Ph2Si-P,P,Si) comprised of a P−P−Si framework was isolated. On the other hand, the reaction between Ph2GeH2 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.