Oxidative addition of Si–H bonds to metal-decorated Zintl clusters [Hyp3Ge9Ir(CO)PR3] (R = Ph, ptolyl, Me)

Abstract

Catalytic reactions with metalated Zintl clusters as catalysts represent a growing research field, whereby the concept of heterogeneous single-site catalysis is transferred towards homogeneous reactions, leading to so-called single-site homogeneous catalysts (SSHoCs). A synthetic protocol for three cluster compounds [Hyp₃Ge₉Ir(CO)PR₃] (Hyp = Si{SiMe₃}₃; R = Ph, ^ptolyl, Me; 1–3) is presented, in which the iridium atom is embedded in the polyhedral cluster surface. The products are characterized by NMR, IR and LIFDI/MS and also structurally characterized for R = Ph by single crystal X-ray structure determination, revealing a closo-[Ge₉Ir] cluster. The exchange of the phosphine ligand of 1 in solution, which is regarded as an important step to create the active site, is investigated for various phosphines. In subsequent reactions, oxidative addition of Si–H bonds of primary and secondary silanes SiHR₂R′ (R/R′ = H/Ph, H/^pMePh, H/^p{OMe}Ph, H/^p{NMe₂}Ph, and Ph/H) to the Ir atom is investigated. The addition reaction is directly monitored by NMR spectroscopy. Additionally, LIFDI/MS, IR spectroscopy, and single crystal structure determination of the addition products confirm the reaction. X-ray photoelectron spectroscopy (XPS) reveals that the transition metal atom and the Ge atoms of the supporting cluster have a low oxidation state.