Polynuclear Gold Complexes of the Carbodiimide Unit [N=C=N]2-

Abstract

Abstract The reaction of N,N′-bis(trimethylsilyl)carbodiimide with equimolar quantities of tris[(triphenylphosphine)gold]oxonium tetrafluoroborate in dichloromethane at -40°C gives high yields of a trinuclear complex {[(Ph3P)Au]2NCN[Au(PPh3)]}+ BF4 -(1). According to variable temperature NMR data the cation is fluxional in solution with a rapid site exchange of the [(Ph3P)Au] units, but has an unsymmetrical (N,N,N′) low temperature ground state configuration. A single crystal X-ray diffraction study has shown that in the crystal lattice these cations are associated further into cyclic, hexanuclear dimers through two short head-to-tail Au-Au contacts (auriophilicity). Treatment of complex 1 with one equivalent of [(Ph3P)Au]+ BF4 - in tetrahydrofuran affords a tetranuclear complex {[(Ph3P)Au]2NCN[Au(PPh3)]2}2+ 2BF4 - (2). The ambient temperature NMR spectra of 2 suggest a fluxional, pseudo-symmetrical structure, but at low temperature a set of three 31P signals (1:2:3 intensity) indicates an aggregation into higher nuclearity species with non-equivalent [Au(PPh3)] units