Synthesis, structure and reactivity of a new six-membered cycloaurated complex of 2-benzoylpyridine [AuCl2(pcp-C1,N)] [pcp equals 2-(2-pyridylcarbonyl)phenyl].: Comparison with the cycloaurated complex derived from 2-benzylpyridin

A six-membered cycloaurated complex [AuCl2(pcp-C-1,N)][pcp = 2-(2-pyridylcarbonyl)phenyl] has been prepared by the reaction between the adduct [AuCl3(Hpcp)] (Hpcp = 2-benzoylpyridine) and AgO2CCF3, and its structure determined by X-ray diffraction. The boat-like conformation of the six-membered pcp-Au ring has been compared to that of the pmp-Au ring in [AuCl(pmp-C-1,N)(PPh3)]BF4 [pmp = 2-(2-pyridylmethyl)phenyl] the structure of which has also been established by X-ray diffraction. The complex [AuCl2(pcp-C-1,N)] reacts with PPh3 in a 1:1 molar ratio to give a neutral complex [AuCl2(pcp)(PPh3)]. This is further converted into trans-[AuCl(pcp)(PPh3)(2)]BF4 and [Au(pcp-C-1,N)(2)]BF4 by treating with PPh3 in the presence of NaBF4 and excess of AgBF4, respectively. This reactivity towards triphenylphosphine has been compared with that of the known cycloaurated complex [AuCl2(pmp-C-1,N)]. Temperature-dependent H-1 NMR spectra attributable to inversion of the six-membered pmp-Au ring have been observed and the rates of inversion measured by line shape analysis of the methylene protons in [AuCl(pmp-C-1,N)(PPh3)]BF4.