| Abstract: | Oxidation of quadruply bonded metal-metal dimers in the presence of good π-accepting ligands results in the formation of MoV---MoV compounds of the type MO2(μ-X)2(Y)(Y′)]2+ (X = O or S; Y,Y′ = O,O; S,S; O,S). Reaction of MO2(O2CCH3)4 with oxygen in the presence of Na2mnt (mnt = 1,2-dicyanoethylene-2,2-dithiolate) gives MO2(μ-S)2(O)(S)(mnt)2]2− (1). The compound crystallizes in the monoclinic space group P21/c, with cell dimensions a = 19.547(4), b = 15.210(4), c = 18.754(6) Å, β = 101.69(2)°, V= 5460(2) Å3, and Z = 4. Similarly, oxidation of o-dichlorobenzene solutions of Mo2Cl4(CH3CN)4 and 4,4′-dimethyl-2,2′-dipyridyl (dmpby) or, more directly, the reaction of Mo2Cl4(dmbpy)2 with oxygen leads to the formation of a red solid, which was characterized by X-ray crystallography to be Mo2(μ-O)2(O)2(Cl)2(dmbpy)2 (2). Red diamond crystals, prepared by slow evaporation of CH3CN solutions of 2, are trigonal and in the space group P3121 with cell dimensions a = 16.135(4), b = 16.135(4), c = 10.709(3) Å, V = 2414.4(13) Å3 and Z = 3. In both structures, the geometry about each of the molybdenum atoms is a distorted square pyramid with terminal oxygen or sulphur atoms at the apices and in a syn conformation. The molybdenum-molybdenum bond distances of 2.858(1) Å and 2.562(2) Å in structures of 1 and 2, respectively, are typical of other MoV---MoV dimers and indicative of a single Mo---Mo bond. |
