Heterolytic bond activation at gold: evidence for gold(III) H–B, H–Si complexes, H–H and H–C cleavage

摘要: The coordinatively unsaturated gold(III) chelate complex [(C^N–CH)Au(C6F5)]+ (1+) reacts with main group hydrides H–BPin and H–SiEt3 in dichloromethane solution at −70 °C to form the corresponding σ-complexes, which were spectroscopically characterized (C^N–CH = 2-(C6H3But)-6-(C6H4But)pyridine anion; Pin OCMe2CMe2O). In presence of an external base such as diethyl ether, heterolytic cleavage silane H–Si bond leads gold [{(C^N–CH)AuC6F5}2(μ-H)]+ (2+) (C^N–CH)AuH(C6F5) (5), together detected [Et3Si–OEt2]+. activation dihydrogen also involves H–H but requires a higher temperature (−20 °C). H2 proceeds two mechanistically distinct steps: first leading 2 plus [H(OEt2)2]+, second protonation one C^N pyridine ligands reductive elimination C6F5H. By comparison, formation by suitably activated C–H bonds is very much more facile; e.g. reaction 1·OEt2 Hantzsch ester essentially instantaneous quantitative −30 °C. This experimental observation species involved initial steps catalyzed hydroboration, hydrosilylation hydrogenation demonstration ability organic act hydride donors towards gold.