Characterization of the adducts formed by Cu(CN) and Cu(NCS) with biquinoline. The crystal structure of the polymeric cyano-compound containing both linear and tetrahedrally co-ordinated copper(I),[{Cu3(bq)2(CN)3}n]

Abstract

The salts Cu(CN) and Cu(NCS) react with 2,2′-biquinoline (bq = C₁₈H₁₂N₂) to give the adducts [{Cu₃(bq)₂(CN)₃}_n](1) and [{Cu₃(bq)₂(NCS)₃}_n](2). Complex (1) crystallizes in space group C2/_m with cell dimensions a= 13.626(2), b= 15.322(2), c= 7.908(1)Å, β= 95.89(1)°, and Z= 2. It consists of chains of CN-bridged copper atoms, each copper being either linearly or tetrahedrally co-ordinated. The tetrahedral copper is also co-ordinated to bq. Pairs of bq molecules belonging to parallel chains stack with an interplanar spacing of 3.35 Å. Complex (2) is microcrystalline and from hot dimethyl sulphoxide gives crystals of [Cu(bq)(NCS)](3). The polarization properties of the i.r. and electronic bands of complex (1) have been determined. In the optical spectrum two metal-to-ligand charge-transfer transitions could be detected. Comparison of the spectroscopic properties of the three compounds indicates a lower degree of polymerization for (3).