Syntheses, structures, and reactivities of heterobimetallic bridging dinitrogen complexes containing group 6 and group 4 or 5 transition metals

A series of heterobimetallic dinitrogen complexes containing group 6 and gr oup 4 or 5 transition metals were synthesized by the reaction of the tungst en or molybdenum dinitrogen complexes cis-[W(N-2)(2)(PMe2Ph)(4)] (1) and tr ans-[M(N-2)(2)(dppe)(2)] (2) (M = W, Mo) with group 4 or group 5 compounds such as [CpTiCl3], [Cp2M'Cl-2] (M' = Ti, Zr, Hf), or [Cp'M'Cl-4] (Cp' = Cp, Cp*; M' = Nb, Ta). Crystallographic studies of the complexes thus obtained including [WCl(PMe2Ph)(4)(mu -N-2)TiCpCl2] and [WCl(PMe2Ph)(4)(mu -N-2)NbC pCl3] revealed that the M-N-N-M' core is essentially linear, and the N-N bo nd is regarded to have the formal bond order of 2. Several mu -N-2 complexe s with methyl ligands at the group 4 or 5 metal center were also obtained t hrough the reaction of dinitrogen complexes 1 and 2a (M = W) with the methy l complexes [Cp2ZrMeCl], [TaMe3Cl2], and [NbMe3Cl3]. The reaction of the co mplex [WCl(dppe)(2)(mu -N-2)TiCpCl2] with Li2S5 afforded the eta (2)-pentas ulfido complex [WCl(dppe)(2)(mu -N-2)TiCpS5], where the eta (2)-S-5 ligand forms a six-membered chelate ring with the chair conformation. Protonation of the mu -N-2 complexes having PMe2Ph ligands gave NH3 in moderate yield, concurrent with the formation of a small amount of NH2NH2.