| Abstract: | Thiocomplexes of Molybdenum. Crystal Structure of a Mixed Single Crystal (PPh3Me)2[Mo2Br6(NO)4]/(PPh3Me)2[Mo2Br6S2(NO)2] The reactions of (PPh4)2MoS4 with MoBr4 and MoBr2(NO)2 resp. lead to the binuclear complexes (PPh4)2[S2MoS2MoBr3(SMe2)] and (PPh4)[S2MoS2MoBr2(NO)2], in which the molybdenum atoms are linked by sulfido bridges. The preparation of (PPh3Me)2S6 and (AsPh4)2S7 from Na2S4 and PPh3MeBr, and AsPh4Cl, respectively, in ethanol solution is described. Disulfido briges are a feature of (AsPh4)2[Mo2Br6(S2)2(SMe2)2], which is obtained from MoBr4(SMe2)2 and (AsPh4)2S7. Mixed single crystals containing 2/3 (PPh3Me)2[Mo2Br6(NO)4] and 1/3 (PPh3Me)2[Mo2Br6S2(NO)2] are formed in the reaction of MoBr2(NO)2 with (PPh3Me)2S6, as shown by X-ray single crystal structure determination. The compound crystallizes monoclinic in the space group C2/c (Internat. Tab. Nr. 15) with four formula units per unit cell (2351 independent observed reflexions, Rw = 0.037). The cell parameters are a = 1603 pm, b = 1549 pm, c = 1863 pm; β = 92.2°. The complexes consist of PPh3Me⊕ cations and the dimeric anions [Mo2Br6(NO)4]2? and [Mo2Br6S2(NO)2]2? which occur in the ratio 2:1. In these the molybdenum atoms are connected via MoBr2Mo bridges of slightly different lengths (Mo? Br 265 pm and 267 pm) forming a controsymmetric double octahedron. All molybdenum atoms have two terminal bromo ligands with Mo? Br bond lengths of 258 pm and 260 pm; in the [Mo2Br6(NO)4]2? ion each molybdenum has two covalently bonded nitrosyl groups on cis-position with Mo? N bond lengths of 183 pm. In the [Mo2Br6S2(NO)2]2? ion one of the two nitrosyl groups at each metal atom is substituted by a terminal sulfido ligand with a Mo? S bond length of 240 pm. The i.r. spectra are reported. |
