N═N Bond Cleavage by Tantalum Hydride Complexes: Mechanistic Insights and Reactivity

Autor: Elena Álvarez-Ruiz, Jorge J. Carbó, Manuel Gómez, Cristina Hernández-Prieto, Alberto Hernán-Gómez, Avelino Martín, Miguel Mena, Josep M. Ricart, Antoni Salom-Català, Cristina Santamaría
Přispěvatelé: Universidad de Alcalá. Departamento de Química Orgánica y Química Inorgánica
Rok vydání: 2021
Předmět:
Zdroj: e_Buah Biblioteca Digital Universidad de Alcalá
instname
Inorganic Chemistry
ISSN: 1520-510X
0020-1669
Popis: The reaction of [TaCpRX4] (CpR = η5-C5Me5, η5-C5H4SiMe3, η5-C5HMe4; X = Cl, Br) with SiH3Ph resulted in the formation of the dinuclear hydride tantalum(IV) compounds [(TaCpRX2)2(μ-H)2], structurally identified by single-crystal X-ray analyses. These species react with azobenzene to give the mononuclear imide complex [TaCpRX2(NPh)] along with the release of molecular hydrogen. Analogous reactions between the [{Ta(η5-C5Me5)X2}2(μ-H)2] derivatives and the cyclic diazo reagent benzo[c]cinnoline afford the biphenyl-bridged (phenylimido)tantalum complexes [{Ta(η5-C5Me5)X2}2(μ-NC6H4C6H4N)] along with the release of molecular hydrogen. When the compounds [(TaCpRX2)2(μ-H)2] (CpR = η5-C5H4SiMe3, η5-C5HMe4; X = Cl, Br) were employed, we were able to trap the side-on-bound diazo derivatives [(TaCpRX)2{μ-(η2,η2-NC6H4C6H4N)}] (CpR = η5-C5H4SiMe3, η5-C5HMe4; X = Cl, Br) as intermediates in the N=N bond cleavage process. DFT calculations provide insights into the N=N cleavage mechanism, in which the ditantalum(IV) fragment can promote two-electron reductions of the N=N bond at two different metal–metal bond splitting stages.
The series of dinuclear tantalum(IV) hydrides [{TaCpRX2}2(μ-H)2] (CpR = η5-C5Me5, η5-C5H4SiMe3, η5-C5HMe4; X = Cl, Br) show the ability to promote N=N bond cleavage in their reactions with azobenzene and benzo[c]cinnoline in absence of reducing reagents. Both the characterization of intermediate species and DFT studies point to a mechanism in two stages, in which the Ta−Ta bond splitting is key for the reduction of the N=N bond and its complete scission.
Databáze: OpenAIRE
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