Preparations and Structures of cis-[Mo2(S2CNC4H4)2(O2CCH3)2OPPh3] and [Mo2(S2PEt3)(O2CCH3)3OPEt3](BF4): Two Quadruply Bonded Dimers Involving Dithio Acid Ligands

The dithiocarbamate of pyrrole (pdc) reacts with molybdenum acetate and triphenylphosphine oxide to give cis-[Mo­2­(pdc)­2­(O­2­CCH­3­)­2­OPPh­3­], which crystallizes with benzene with 1½ molecules of solvent per dimer in the triclinic space group P1 with unit cell parameters a = 11.777 (2) Å, b = 16.690 (2) Å, c = 11.535 (3) Å, α = 95.4 (2)°, β = 102.07 (2)°, γ = 84.23 (1)°, V = 2197.9 Å3, and Z = 2. The reaction of molybdenum acetate with the zwitterionic S­2­CPEt­3­ in the presence of HBF­4­ yields the dimer [Mo­­­2­(S­2­CPEt­3­)(O­2­CCH­3­)­3­OPEt­3­](BF­­­4­) which crystallizes in the monoclinic space group P2­1­/c with unit cell parameters a = 13.186 (2) Å, b = 14.403 (3) Å, c = 17.882 (4) Å, β = 106.97 (1)°, V = 3248.3 Å3, and Z = 4. In both dimers, one molybdenum is axially coordinated to the oxygen of the phosphine oxide and the other to the oxygen of an acetate on an adjacent dimer. The Mo-O distances for the oxygen of the phosphine oxide are the shortest observed for axial coordination. Both sulfur ligands are in the dithio acid resonance form