ACTIVATED MOLYBDENUM-MOLYBDENUM QUADRUPLE BONDS - SYNTHESIS, STRUCTURE, AND PROPERTIES OF [MO2(O2CME)2(EN)4][(O2CME)2].EN - A SOLID-STATE MODEL FOR A SOLVENT-SHARED ION-PAIR

{formula-omited} reacts with neat ethylenediamine (en) to form [Mo2(O2CMe)2(en)4][(O2CMe)2]•en (1) in high yield. The Mo2(O2CMe)2(en)42+ ion in 1 contains a quadruply bonded Mo24+ center [Mo−Mo = 2.125 (1) Å] supported by two axial and two spanning en ligands in addition to two spanning acetates. The complex exists as an ion pair in which the displaced acetates are separated from the Mo2 coordination sphere by the two spanning en ligands. The acetate counterions are hydrogen bonded to the spanning en ligands [N−O = 2.86 (2) Å (av)]. Compound 1 converts back to Mo2(O2CMe)4 at 120 °C in the solid state. NMR studies show that dissociated and coordinated acetate ligands are present in neat en whereas, in D2O, only dissociated en and acetate are observed. Crystal data for 1 (20 °C): a = 25.548 (7) Å, b = 9.277 (3) Å, c = 14.292 (4) Å, β = 107.43 (2)°, Z = 4, Dcalc = 1.374 g/cm3, and space group C2/m. © 1990, American Chemical Society. All rights reserved.