Synthesis, Structure, and Electrochemical Studies of Molybdenum and Tungsten Dinitrogen, Diazenido, and Hydrazido Complexes That Contain Aryl-Substituted Triamidoamine Ligands

Abstract

One-electron reduction of [ArN(3)N]MoCl complexes (Ar = C(6)H(5), 4-FC(6)H(4), 4-t-BuC(6)H(4), 3,5-Me(2)C(6)H(3)) yields complexes of the type [ArN(3)N]Mo-N=N-Mo[ArN(3)N], while two-electron reduction yields ([ArN(3)N]Mo-N=N)(-) derivatives (Ar = C(6)H(5), 4-FC(6)H(4), 4-t-BuC(6)H(4), 3,5-Me(2)C(6)H(3), 3,5-Ph(2)C(6)H(3), and 3,5-(4-t-BuC(6)H(4))(2)C(6)H(3)). Compounds that were crystallographically characterized include ([t-BuC(6)H(4)N(3)N]Mo)(2)(N(2)), Na(THF)(6)([PhN(3)N]Mo-N=N)(2)Na(THF)(3), [t-BuC(6)H(4)N(3)N]Mo-N=N-Na(15-crown-5), and ([Ph(2)C(6)H(3)N(3)N]MoNN)(2)Mg(DME)(2). Compounds of the type [ArN(3)N]Mo-N=N-Mo[ArN(3)N] do not appear to form when Ar = 3,5-Ph(2)C(6)H(3) or 3,5-(4-t-BuC(6)H(4))(2)C(6)H(3), presumably for steric reasons. Treatment of diazenido complexes (e.g., [ArN(3)N]Mo-N=N-Na(THF)(x)) with electrophiles such as Me(3)SiCl or MeOTf yielded [ArN(3)N]Mo-N=NR complexes (R = SiMe(3) or Me). These species react further to yield ([ArN(3)N]Mo-N=NMe(2))(+) species in the presence of methylating agents. Addition of anionic methyl reagents to ([ArN(3)N]Mo-N=NMe(2))(+) species yielded [ArN(3)N]Mo(N=NMe(2))(Me) complexes. Reduction of [4-t-BuC(6)H(4)N(3)N]WCl under dinitrogen leads to a rare ([t-BuC(6)H(4)N(3)N]W)(2)(N(2)) species that can be oxidized by two electrons to give a stable dication (as its BPh(4)(-) salt). Reduction of hydrazido species leads to formation of Mo=N in low yields, and only dimethylamine could be identified among the many products. Electrochemical studies revealed expected trends in oxidation and reduction potentials, but also provided evidence for stable neutral dinitrogen complexes of the type [ArN(3)N]Mo(N(2)) when Ar is a relatively bulky terphenyl substituent.

Die katalytische Reduktion von Distickstoff zu Ammoniak mit Molybdän: Theorie und Experiment

“…[27][28][29] 3À , in denen R eine gewöhnliche Arylgruppe ist, am einfachsten durch eine Buchwald-HartwigArylierung von Triethylentetramin erhalten. [31,32] Wir wendeten uns dann Molybdänkomplexen mit dem [HIPTN 3 N] 3À -Liganden zu (HIPT = 3,5-(2,4,6-iPr 3 C 6 H 2 ) 2 C 6 H 3 , Hexaisopropylterphenyl; Schema 1), [33,34] Für eine hypothetische "lineare" Reduktion von N 2 wurden Intermediate vorgeschlagen (Schema 2), von denen die folgenden acht synthetisiert und kristallographisch und mit anderen Verfahren charakterisiert wurden: [33][34][35][36] 3À leicht modifiziert waren, [40,41] und neuere Befunde bei der Reduktion von Distickstoff zusammengefasst. [42][43][44] Die eingesetzte Säure beeinflusst den Erfolg der Reduktion sehr stark.…”

Activation of Molecular Nitrogen: Coordination, Cleavage and Functionalization of N2 Mediated By Metal Complexes

“…[112] A new report has shown that modifying the ligand with various aryl-based substituents changes the observed reactivity slightly. As shown in Scheme 7, the [113] While the end-on dinitrogen complexes discussed above used alkali metals to promote reactivity, the slight polarity of the side-on end-on dinitrogen complex Scheme 5. …”

Portability of the RNNMo(3+) core — Application to the synthesis of dinitrogen-derived trialkoxymolybdenum organodiazenido complexes

“…3 There has long been interest in the conversion of dinitrogen-derived hydrazido systems to amines, and it has been shown that treatment of cationic hydrazido complexes with LiAlH 4 can effect the conversion (37). Although not a clean transformation, it has been shown that [{ArN 3 N}MoNNMe 2 ]OTf upon reduction with Na-Hg in THF undergoes N-N bond cleavage producing nitride [ArN 3 N]MoN together with dimethylamine and other products (38), implying that neutral dimethylhydrazido complex [ArN 3 N]MoNNMe 2 lacks sufficient stability for isolation. Presumably, fragmentation of the latter neutral system leads to nitride along with the [NMe 2 ] radical, the latter being (7).…”