Di(2-pyridyl) ketone complexes of CuI- and Cu II-containing iodide and thiocyanate ligands: An unusual case of a mixed-aldol condensation

Abstract

Complexes containing di(2-pyridyl) ketone (dpk) as a bi- (N,N) and tridentate (N,N,O) ligand have been synthesised1,2 and characterized by spectral and structural studies. Products 1 and 2 are polymorphs of the polymeric copper(I) complex [Cu(dpk)(NCS)]n containing dpk with thiocyanate anions which bridge to form a one-dimensional continuous polymer chain. The novel dinuclear copper(II) complex [Cu2(dpk·acetone) 2(NCS)2] (3) was formed when 1 and 2 were allowed to stand in the supernatant. In this instance it appears that a transition-metal- promoted aldol condensation has occurred between the solvent acetone and the ketone carbonyl of dpk to produce the novel ligand, dpk·acetone. Product 3 contains two five-coordinate copper(II) ions, both with trigonal bipyramidal coordination, bridged through deprotonated hydroxy groups on each dpk·acetone. A chemical rationalisation for the formation of 3 is proposed. The dinuclear copper(I) complex [Cu2(dpk)2I 2] (4) is also reported, which contains two four-coordinate copper(I) ions that are bridged together through iodide ions. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.