A13C nuclear magnetic resonance study of some linear alkynyl gold(I) and silver(I) complexes

Abstract

Phenylacetylide gold(I) and silver(I) compounds of the type [n-Bu4N][M(C=CPh)2], (1) and [n-Bu4N][XMC=CPh], (2) have been studied by13C n.m.r. spectroscopy and their chemical shifts are reported for the first time. The shielding of the alkynyl carbon linked directly to the metal in (2) isca. 10–15 ppm less than the analogous carbon in (1) (M=Au), andca. 6–11 ppm less in the silver complexes (M=Ag). The variation in chemical shift depends on the nature of X(X=Cl, Br, I, C2Ph and Ph3P) and indicates greatly different degrees of polarization of the Au-C= (or Ag-C=) bonds in (1) and (2). I.r. spectra of the title compounds are reported and confirm the weakness of ML π back-bonding. Comparison is also made with13C and i.r. data for platinum, and mercury complexes.