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

Abstract

Reaction of Mo(CO) 6 with excess N, N′-di(3-methoxyphenyl)formamidine (HDmAniF) in o-dichlorobenzene afforded the yellow complex Mo 2(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 Me 3OBF 4 in CH 3CN gave cis-[Mo 2(DmAniF) 2(CH 3CN) 4][BF 4] 2, 2, which crystallized in two different forms. The first form, 2·CH 2Cl 2·CH 3CN, 2a, showing one BF 4 - 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, 2·0.5CH 2Cl 2 · 0.5CH 3CN, 2b, involves two independent molecules. While one [Mo–Mo = 2.1432(8) Å] of the two molecules shows axial interaction by CH 3CN [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 Mo 2(μ 2-L) 2(CH 3CN) 4 core, where L is the anionic, cationic or neutral form of a formamidine ligand. Reaction of 2 with NaOCH 3 in CH 3OH produced the tetranuclear complex cis-[Mo 2(DmAniF) 2] 2(μ-OCH 3) 4, 3. The molecule of 3 bears four bridging CH 3O − groups that link two quadruply bonded moieties and the ligands adopts the s- trans, s- trans conformation.