Photoluminescent metal-sulfur clusters derived from tetrathiometalates: Metal-to-metal charge-transfer excited states of d 0-d 10 heterobimetallic sUlfido clusters with bulky phosphine ligands

Abstract

Reactions of MS 4 2- (M = Mo, W) with M′(PCy 3)X (M′ = Ag/Au, X = ClO 4/Cl) and [Cu 2(dcpm) 2(MeCN) 2]-(ClO 4) 2 (dcpm = bis(dicyclohexylphosphino)methane) afforded heterometallic sulfido clusters [M′ 2(PCy 3) 2(MS 4)] (M = Mo, M′ = Au: 2; M = W, M′ = Ag: 3, Au: 4) and [Cu 4(dcpm) 4(MS 4)](ClO 4) 2 (M = Mo: 5·(ClO 4) 2, W: 6·(ClO 4) 2), all of which, except 4, have been characterized by X-ray structure determination. Clusters 5·(ClO 4) 2 and 6·(ClO 4) 2 feature unusual 16-membered {Cu 4P 8C 4} metallamacrocycles formed on the respective tetrathiometalate anion templates and have unusually long Cu-S bonds and Cu-M distances for metal-sulfur clusters that contain a saddle-shaped {Cu 4MS 4} core. Low-energy absorption bands are observed in their electronic spectra at ∼562 and 467 nm, respectively, assignable to MMCT tran-sitions; quasireversible reduction waves are observed with E 1/2 = -1.43 (5 2+) and -1.78 V (6 2+) versus FeCp 2 0/+; and they are emissive either in the solid state or in solution. The emission of 6 2+ can be quenched by both electron acceptors, such as methylviologen, or electron donors, such as aromatic amines, with the excited state reduction potential E(6 2+*/6 +) estimated to be ∼1.13 V versus a normal hydrogen electrode. © Wiley-VCH Verlag GmbH, 2001.