Synthesis, structural characterization and photophysical properties of ethyne-gold(I) complexes

Abstract

A series of closely related ethynyl-gold(I) complexes was synthesized by reaction of Au(PR 3)Cl with an alkaline solution of the ethyne. The molecular structures of the ethynediyl-digold complexes NpPh 2PACCAuPNpPh 2·2CHCl 3 (1) (Np = naphthyl), Np 2PhPAuCCAuPNp 2Ph·6CHCl 3 (2) and Fc 2PhPAu CCAuPFc 2Ph·4EtOH (3) (Fc = ferrocenyl) and the phenylethynyl-gold complex Fc 2PhPAuC CPh (4) were determined by single-crystal X-ray diffraction measurements. Variation of the phosphines does not have a significant influence on the bonding in the central PAuCC unit, the AuP and AuC distances being in the ranges 2.274(4)-2.289(5) and 1.983(8)-2.002(6) Å, respectively. Although none of the compounds have short Au⋯Au contacts, compounds 1 and 2 do show novel CH⋯π interactions between the proton of CHCl 3 and the π-electron system of the CC bond. In 1, pairs of CHCl 3 molecules are located with their protons 2.4 Å from the centre of the CC bond with the C H bond directed orthogonally towards the centre of the ethyne bond. In 2, two pairs of CHCl 3 molecules are located around the CC bond, with 2.5 Å between the proton and the centre of the triple bond, resulting in a pseudo-octahedral arrangement around CC. In addition to the CH⋯π interactions, the structures of 1 and 2 also show a range of intermolecular aromatic-aromatic interactions. The first structural determination of naphthylphosphines resulted in estimates of their steric requirements. The UV-visible spectra of CH 2Cl 2 solutions of the ethynediyl compounds exhibit intense absorption bands at ca. 300 nm assignable to intraligand transitions. Excitation of solid sample or fluid solution of complex 1 at λ > 330 nm resulted in intense long-lived luminescence. Excitation of a solution of 2 at 350 and 380 nm led to different types of photoluminescence. © 1994.