Crystal structures of some complexes of group IB ethynyl compunds

Abstract

Interest in these compounds centred on the bonding between the ethynyl groups and the metal atoms. The structures were determined by heavy atom techniques, and refined by the method of least squares, using three-dimensional data. Phenylethynyl(trimethylphosphine)copper(l), Me(_3)PCuC≡CPh, is tetrameric. The centresymmetric molecules are nearly flat, apart from the phosphine groups. The four copper atoms form a zig-zag chain, with Cu...Cu distances 2.45, 2.69, 2.4-5 Ǻ. Two phosphine groups are attached to each terminal copper atom. Two of the ethynyl groups lie on a line through the two inner copper atoms, to which they are σ-bonded. The other two are each 'side-on' bonded to an inner copper atom, with the bond to the phenyl group distorted away from the copper atom. Their terminal carbon atoms each form a bridge bond with two further copper atoms in the chain. Neglecting any copper- copper interaction, the coordination around the inner copper atoms is approximately trigonal, and around the terminal copper atoms, tetrahedral. Phenylethynyl(trimethylphosphine)silver(I), Me(_3)PAgCsC≡h , has silver atoms in infinite, almost straight, chains, with Ag...Ag = 3.03 Ǻ. Alternate silver atoms lie on centres of symmetry, and are σ-bonded to two ethynyl groups. These are 'side-on' bonded to adjacent silver atoms, which lie on two-fold axes, and which are bonded to two phosphine groups. The 'side-on' bonding is not symmetrical. (Ag-C = 2.55, 3.04 Ǻ.) The silver atoms are alternately in linear, and approximately tetrahedral, coordination. Phenylethynyl(isopropylamine)gold(I), (^i)PrfNH(_2)AuC≡CPh, has gold atoms in infinite zig-zag chains, related in pairs by two-fold axes. Au. ..Au = 3.72 2 Ǻ. along the chains, 3.27 Ǻ. Between chains. Each gold atom is linearly coordinated to an ethynyl carbon and an amine nitrogen atom, lying in the plane of the zig-zag. The arrangement excludes association through gold-ethynyl interaction, the shortest intermolecular distances being gold- gold or gold-nitrogen contacts.