Trapping Tetramethoxyzincate and -cobaltate(II) between Mo24+ Units

Two compounds of a new type, [Mo2](CH3O)2M(CH3O)2[Mo2] where [Mo2] is an abbreviation for Mo2[(p-MeOC6H4)NCHN(p-MeOC6H4)]3 and M = Zn (1) and Co (2), are reported. Discrete [M(OR)4]2- ions, either as such or in the μ24 role, have not heretofore been described. In these compounds they have distorted tetrahedral structures and bridge two [Mo2] groups in much the same way as did SO42-, MoO42-, and WO42- ions in other recently reported compounds (Cotton, F. A.; Donahue, J. P.; Murillo, C. A. Inorg. Chem. 2001, 40, 2229). The 1H NMR spectrum of 1 and the visible spectrum and magnetic properties of 2 are consistent with these structures. The M(OCH3)4 bridges are moderately effective in coupling the two [Mo2] redox centers. Compounds 1 and 2 may also be viewed as having ZnII and CoII centers tetrahedrally coordinated by the bidentate ligand [Mo2[(p-MeOC6H4)NCHN(p-MeOC6H4)]3(OMe)2]-. From that point of view they may be compared with Zn(DPM)2 and Co(DPM)2 (3), where DPM is the anion of dipivaloylmethane. For purposes of comparison, 3 has been fully characterized structurally, spectroscopically, and magnetically. Close analogies between 2 and 3 are shown to exist.