Synthesis, crystal structures and third-order nonlinear optical properties of a new family of double incomplete cubane-like clusters [(η5-C5Me5)2Mo2(μ3-S)3SCu2X(μ-X)]2 (X = Cl−, Br−, SCN−) and cubane-like clusters [(η5-C5Me5)2Mo2(μ3-S)4(CuX)2] (X = Br−, S

Reactions of trans-[(η5-C5Me5)2Mo2(μ-S)2S2] (1) with 2 equiv. of CuX (X = Cl−, Br−, SCN−, CN−) in refluxing acetonitrile resulted in a new set of Mo/Cu/S cluster compounds [(η5-C5Me5)2Mo2(μ3-S)3SCu2Cl(μ-Cl)]2 (2), [(η5-C5Me5)2Mo2(μ3-S)4(CuBr)2] (3) and [(η5-C5Me5)2Mo2(μ3-S)3SCu2Br(μ-Br)]2 (4), [(η5-C5Me5)2Mo2(μ3-S)4(CuSCN)2] (5) and [(η5-C5Me5)2Mo2(μ3-S)3SCu2(SCN)(μ-SCN)]2 (6) and [(η5-C5Me5)2Mo2(μ3-S)4(CuCN)2] (7). Compounds 2–7 were fully characterized by elemental analysis, IR, UV–Vis, 1H NMR and single-crystal X-ray crystallography. Compounds 2, 4 and 6 consist of two incomplete cubane-like [(η5-C5Me5)2Mo2(μ3-S)3SCu2X] species bridged by a pair of μ-X− anions while 3, 5 and 7 contain a cubane-like [(η5-C5Me5)2Mo2(μ3-S)4Cu2] core with each of two terminal X− coordinated at each copper(I) center. The third-order nonlinear optical (NLO) properties of 2–5 and 7 along with [(η5-C5Me5)2Mo2(μ3-S)4(CuCl)2] in CH2Cl2 were investigated by using Z-scan technique at 532 nm. All these clusters showed strong third-order NLO absorption effects and self-defocusing properties.