Syntheses, crystal structures and optical limiting properties of three novel organometallic tungsten-copper-sulfur clusters:: [PPh4][(η5-C5Me5)WS3(CuCN)2], [(η5-C5Me5)WS3Cu2(PPh3)(μ-CN)]2 and [PPh4]{(η5-C5Me5)WS3Cu2(CN)(Py)}2(μ-CN)]

Reactions of [PPh4][(eta(5)-C5Me5)WS3] with two equivalents of CuCN in MeCN produced a novel trinuclear butterfly-shaped cluster [PPh4][(eta(5)-C5Me5)WS3(CuCN)(2)] (1) in a 70% yield. Treatment of I with excess PPh3 or Py gave rise to two different hexanuclear clusters [(eta(5)-C5Me5)WS3Cu2(PPh3)(mu-CN)](2) (2) and [PPh4][{(eta(5)-C5Me5)WS3Cu2(CN)(Py)}(2)(mu-CN)] (3), respectively. Compounds 1-3 were fully characterized by spectroscopy and X-ray crystallography. The structure of the cluster anion of 1 contains a butterfly-like WS3Cu2 fragment in which each Cu atom is coordinated to one mu-S atom, one mu(3)-S atom, and one terminal CN group. The neutral compound 2 has a double butterfly-shaped structure in which two WS3Cu2 fragments are interconnected by two Cu-mu-CN-Cu bridges. The anion of 3 adopts another type of double butterfly-shaped structure in which the two WS3Cu2 fragments are linked by a single Cu-mu-CN-Cu bridge. Compared with C-60 in terms of the optical limiting (OL) properties measured under identical conditions, 1 and 2 exhibit a relatively good OL performance, whereas the OL effect is not observed for 3. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).