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

Abstract

A six-membered cycloaurated complex [AuCl₂(pcp-C¹,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-C¹,N)(PPh₃)]BF₄ [pmp = 2-(2-pyridylmethyl)phenyl] the structure of which has also been established by X-ray diffraction. The complex [AuCl₂(pcp-C¹,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-C¹,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-C¹,N)]. Temperature-dependent ¹H 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-C¹,N)(PPh₃)]BF₄.