Thiolate coordination in binuclear oxomolybdenum(V) complexes. The x-ray crystal structures of the alkylammonium salts of [Mo₂O₂(OCH₃)(SCH₂CH₂CH₂S)₃]^- and [Mo₂O₂(SCH₂CO₂)₄]^2-

Reaction of [n-Bu₄N]₂[Mo₂O₇] with propane-1,3-dithiol in methanol yields the triply-bridged binuclear complex [n-Bu₄N][Mo₂O₃(OCH₃)(SCH₂CH₂CH₂S)₃] (1). Complex 1 exhibits the confacial bioctahedral geometry characteristic of this class of complexes. In contrast, the reaction of [n-Bu₄N]₄[Mo₈O₂₆] with 2-mercaptoacetic acid and triethylamine in methanol results in the isolation of a complex [Et₃NH]₂[Mo₂O₂(SCH₂CO₂)₄] (2), representing the first example of a new class of binuclear molybdenum(V) species. The structure is characterized by a 'trans-planar' [Mo₂O₂S₂(thiolate)]⁴⁺ core and an unusually long Mo ⋯ Mo distance of 3.078(1) Å. Crystal data. Complex 1: triclinic space group P1, a = 9.310(2), b = 11.328(2), c = 19.954(3) Å, α = 74.93(1), β = 78.19(1), γ = 81.53(1)°, V = 1979.2(10) ų, Z = 2, D_calc, = 1.369 g cm^3-; structure solution and refinement based on 5292 reflections, R = 0.0570. Complex 2: monoclinic space group P2₁/n, a = 10.861(4), b = 13.559(4), c = 11.011(4) Å, β = 104.14(2)°, V = 1572.1(11) ų, Z = 2, D_calc, = 1.664 g cm^-3; 2133 reflections, R = 0.0560.