Synthesis and structures of the WOS 3Cu 3Pz 3Cl and [PPh 4] 4[{WOS 3(CuNCSe) 3} 2] clusters (Pz=pyrazole), and structure of [PPh 4] 2[Cu(NCS) 4

Abstract

Reaction of CuCl and pyrazole (Pz) with [NH 4] 2[WOS 3] in acetone yields a new cluster WOS 3Cu 3Pz 3Cl ( 1), forming a one-dimensional polymer through secondary CuCl bonding, while [PPh 4] 4[{WOS 3(CuNCSe) 3} 2] ( 2) with selenocyanate bridges in the dimeric anion is formed by the reaction of CuCl and KSeCN with [PPh 4] 2[WOS 3] in acetone solution. The title compounds have been characterized by single-crystal X-ray diffraction, IR and UV–Vis spectroscopy. We also present the temperature-dependent 1H NMR spectrum of WOS 3Cu 3Pz 3Cl. Crystals of [PPh 4] 2[Cu(NCS) 4] ( 3) have been obtained during the slow evaporation of a dichloromethane solution of [PPh 4] 2[Co(WO 2S 2) 2(CuNCS) 2]. The two compounds 1 and 2 contain approximately tetrahedral WOS 3 units and all metal atoms and sulfur atoms form incomplete cubane-type frameworks; the eighth vertex opposite W is vacant. Thiotungstate groups in 1 and 2 act as bidentate ligands through two sulfur atoms chelating copper atoms. This is consistent with the infrared spectra, which exhibit low frequency W–S b stretching bands. There is no coordination of oxygen atoms to copper. In each of 1 and 2 two distinctly different coordination geometries of copper are found: two copper atoms adopt trigonal planar geometry, while the third one adopts distorted tetrahedral geometry. Compound 3 has an essentially regular tetrahedral geometry, unusual for Cu(II).