Chemistry of dimolybdenum complexes containing bridging anions of N,N′-di(3-methoxyphenyl)formamidine

Reaction of Mo(CO)6 with excess N,N′-di(3-methoxyphenyl)formamidine (HDmAniF) in o-dichlorobenzene afforded the yellow complex Mo2(DmAniF)4, 1. The structure of 1 reveals that the ligands bridge the two metal centers through the two nitrogen atoms, forming two s-cis, s-trans and two s-trans, s-trans conformations. Reaction of 1 with Me3OBF4 in CH3CN gave cis-[Mo2(DmAniF)2(CH3CN)4][BF4]2, 2, which crystallized in two different forms. The first form, 2·CH2Cl2·CH3CN, 2a, showing one BF4- anion coordinating to the axial positions of the Mo–Mo bond [Mo⋯F = 2.685(4) Å], contains two cis DmAniF− ligands which adopt the same s-cis, s-trans conformation. The other form, 2·0.5CH2Cl2 · 0.5CH3CN, 2b, involves two independent molecules. While one [Mo–Mo = 2.1432(8) Å] of the two molecules shows axial interaction by CH3CN [Mo⋯N = 2.692(8) Å] and the two cis DmAniF− ligands adopt the same s-cis, s-trans conformation, the other one [Mo-Mo = 2.1317(9) Å] shows no axial interaction and the two cis DmAniF− ligands adopt different conformations, which are s-cis, s-trans and s-cis, s-cis, respectively. The Mo–Mo distance of 2a, 2.1281(6) Å, is the shortest among the compounds having Mo2(μ2-L)2(CH3CN)4 core, where L is the anionic, cationic or neutral form of a formamidine ligand. Reaction of 2 with NaOCH3 in CH3OH produced the tetranuclear complex cis-[Mo2(DmAniF)2]2(μ-OCH3)4, 3. The molecule of 3 bears four bridging CH3O− groups that link two quadruply bonded moieties and the ligands adopts the s-trans, s-trans conformation.