Homobimetallic bis-NHC(Ptdvtms)2 Complexes for the Hydrosilylation of Alkenes

Abstract

A series of six bimetallic bis-NHC(Ptdvtms)2 complexes 1–6 (dvtms = 1,1,3,3-tetramethyl-1,3-divinyldisiloxane) has been designed by expansion of the monometallic Markó-type system in anticipation of synergistic bimetallic cooperation. The new compounds are easily accessible using Karstedt's catalyst [Pt2(dvtms)3] as platinum(0) precursor and the respective bis-(imidazolium) salts (L1–6), deprotonated by potassium tert‑butoxide. Characterization via NMR spectroscopy (1H, 13C, 29Si, 195Pt) and SC-XRD reveals a strong similarity of this new complex class to the parent monometallic complexes. The hydrosilylation reactions of oct-1-ene or 1,1,1,3,3-pentamethyl-3-vinyldisiloxane (MMVi) with 1,1,3,5,5-heptamethyltrisiloxane (MDHM), respectively, are efficiently and selectively catalyzed with turn-over frequencies (TOF) of up to 78,000 h–1 after a significantly shortened induction period compared to their monometallic relatives. Mercury poisoning experiments demonstrate the superiority of bimetallic compared to monometallic systems in terms of stability when exposed to silanes.