COVALENTLY-LINKED MOLYBDENUM MOLYBDENUM QUADRUPLE BONDS - DIOXYPYRIDAZINE DIANION AND 2-IMIDAZOLINETHIONATE AS BRIDGES BETWEEN DIMOLYBDENUM FRAGMENTS

[Mo2(O2CBut)3(CH3CN)2]+[BF4]- and the disodium salt of the dioxypyridazine dianion (DOP) react in CH2Cl2/CH3CN/MeOH solution to give the red microcrystalline tetranuclear compound [Mo2(O2CBUt)3]2(mu-DOP) (1), which is soluble in coordinating solvents such as THF and pyridine (py). Compound 1 shows two oxidation potentials by cyclic voltammetry, 1 --> 1+, E1/2 = - 0.15 V, and 1+ --> 1(2+), E1/2 = +0.28 V, vs the CP2Fe/CP2Fe+ couple. The first oxidation is chemically reversible and the cationic complex [1]+[BF4]- was isolated. The reaction between [Mo2(O2CBUt)3(CH3CN)2]+[BF4]- and the sodium salt of the dianion derived from deprotonation of 2-imidazolinethione in a CH2Cl2/CH3CN/MeOH solvent mixture gave Mo2(O2CBUt)3(IMT) (2), where IMT represents the anion from a single deprotonation of 2-imidazolinethione. Compound 2 was structurally characterized as its pyridine adduct 2 . (py)2 and contained a central Mo-4Mo bond, 2.116(1) angstrom, bridged by three O2CBut ligands and an IMT ligand which forms Mo-N and Mo-S bonds of lengths 2.12(1) and 2.49(1) angstrom, respectively. The two molecules of pyridine are coordinated along the Mo-Mo axis, one in a rather normal manner, Mo-N = 2.63(1) angstrom, but the other in a more distant arrangement with Mo --- N = 2.97(1) angstrom. The latter py is coordinated to the molybdenum atom that is bonded to the nitrogen atom of the IMT ligand. These results are compared with those of earlier studies aimed at covalently linking M-4M bonds.