Synthesis, structure, and electrochemical studies of molybdenum and tungsten dinitrogen, diazenido, and hydrazido complexes that contain aryl-substituted triamidoamine ligands

One-electron reduction of [ArN3N]MoCl complexes (Ar = C6H5, 4-FC6H4, 4-t-Bu C6H4, 3,5-Me2C6H3) yields complexes of the type [ArN3N]Mo-N=N-Mo[ArN3N], wh ile two-electron reduction yields {[ArN3N]Mo-N= N}(-) derivatives (Ar = C6H 5, 4-FC6H4, 4-t-BuC6H4, 3,5-Me2C6H3, 3,5-Ph2C6H3, and 3,5-(4-t-BuC6H4)(2)C6 H3)Compounds that were crystallographically characterized include {[t-BuC6H 4N3N]Mo}(2)(N-2), Na(THF)(6){[PhN3N]MoN=N}(2)Na(THF)(3), [t-BuC6H4N3N]Mo-N= N-Na(15-crown-5), and {[Ph2C6H3N3N]MoNN}(2)Mg(DME)(2). Compounds of the typ e [ArN3N]Mo-N=N-Mo[ArN3N] do not appear to form when Ar = 3,5-Ph2C6H3 or 3, 5-(4t-BuC6H4)(2)C6H3, presumably for steric reasons. Treatment of diazenido complexes (e.g., [ArN3N]Mo-N=NNa(THF)(x)) with electrophiles such as Me3Si Cl or MeOTf yielded [ArN3N]Mo-N=NR complexes (R = SiMe3 or Me). These speci es react further to yield {[ArN3N]Mo-N=NMe2}(+) species in the presence of methylating agents. Addition of anionic methyl reagents to {[ArN3N]Mo-N=NMe 2}(+) species yielded [ArN3N]Mo(N=NMe2)-(Me) complexes. Reduction of [4-t-B uC6H4N3N]WCl under dinitrogen leads to a rare {[t-BuC6H4N3N]W}(2)(N-2) spec ies that can be oxidized by two electrons to give a stable dication (as its BPh4- salt). Reduction of hydrazido species leads to formation of Mo dropN in low yields, and only dimethylamine could be identified among the many p roducts. Electrochemical studies revealed expected trends in oxidation and reduction potentials, but also provided evidence for stable neutral dinitro gen complexes of the type [ArN3N]Mo(N-2) when Ar is a relatively bulky terp henyl substituent.