SYNTHESIS, REACTIVITY AND REDOX PROPERTIES OF DINUCLEAR MOLYBDENUM-SULFUR COMPLEXES

This paper reports the synthesis of dinuclear Mo(V) complexes containi ng the Mo2S42+ core. Complexes are prepared using the starting materia l (NH4)(2)MO(2)(S-2)(6) .2H2O for which a new high yield preparation i s presented. Reaction of Mo-2(S-2)(6)(2-) With eight equivalents of th e monodentate thiol, PhSH, gives Mo2S82-, i.e. (eta(2)-S-2)MoS(mu-S)(2 )Mo(eta(2)-S-2)(2-), which has one terminal disulfido and one sulfide ligand in each molybdenum coordination sphere and has a bis(sulfido) b ridge rather than the bis(disulfido) bridge of the starting material. The Mo2S82- anion is identical to that formed by the reaction of MoS42 - with PhSSPh by an induced internal electron transfer process. Reacti on of (NH4)(2)Mo-2(S-2)(6) . 2H(2)O with a large excess of PhSH yields Mo2S4(SPh)(4)(2-) in which the Mo2S42+ core is bound by four monodent ate thiolate ligands. The reaction of (NH4)(2)Mo-2(S-2)(6) . 2H(2)O Wi th excess of a variety of S-containing bidentate ligands gives high yi elds of Mo2S42+ core products with one bidentate, dithiolate on each m olybdenum. The reactions involve reduction of the disulfido ligands in Mo-2(S-2)(6)(2-) to sulfide ligands, four of which remain in the coor dination spheres of the two molybdenum atoms. All reactions and interc onversions involve the maintenance of molybdenum in the oxidation stat e V. The complexes are of the general form Mo(2)S(4)L(2)(n-)(n = 0, L = i-Bu(2)NCS(2), Et(2)NCS(2), NH(CH3)CH2C(CH3)S, NH2CH2C(CH3)S, C6H4SN H2; n = 2, C6H4S2, CH3C6H3S2, C6H4SNH, SCH2CH2S). The X-ray crystal st ructures of (PPh(4))(2)[Mo2S8] and (NMe(4))(2)[Mo2S4(SPh)(4)] are repo rted. The structures are compared with other crystallographically char acterized complexes containing the syn and anti Mo2S42+ cores. Infrare d and UV-visible spectroscopic and electrochemical data are given for all of the new complexes reported.