Structure and bonding in gold(I) compounds. Part 4. A phosphorus-31 nuclear magnetic study of the structure of some gold(I) phosphine complexes in solution

Abstract

The addition of PEt₃ to dichloromethane solutions of [Au(PEt₃)₂][PF₆] or [Au(PEt₃)Cl] at 175 K leads to the formation in solution of three- and four-co-ordinate gold(I) complexes. These are of the type [AuL_n]⁺(n= 3 or 4) and there is no evidence in the case of [Au(PEt₃)Cl] for the presence of the undissociated species [AuL_nCl](n > 1) under these conditions. When P(OEt)₃ is added to solutions of the above complexes, mixed species of the type [Au(PEt₃)_n{P(OEt)₃}_4-n]⁺(n= 1–3) are formed. If the amount of P(OEt)₃ added is such as to give a total ligand : gold ratio of <4 : 1 the two- and three-co-ordinate complexes which are present contain only PEt₃. In no case has free ligand [PEt₃ or P(OEt)₃] been observed to be present until the ligand : gold ratio exceeded 4 : 1. At >213 K, ligand exchange is rapid on the n.m.r. time scale in all the systems studied.