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

Identifier:  imarina:9242328

Handle: https://hdl.handle.net/20.500.11797/imarina9242328

Authors:  Alvarez-Ruiz, Elena; Carbo, Jorge J; Gomez, Manuel; Hernandez-Prieto, Cristina; Hernan-Gomez, Alberto; Martin, Avelino; Mena, Miguel; Ricart, Josep M; Salom-Catala, Antoni; Santamaria, Cristina

Abstract:
The reaction of [TaCpRX4] (CpR = ?5-C5Me5, ?5-C5H4SiMe3, ?5-C5HMe4; X = Cl, Br) with SiH3Ph resulted in the formation of the dinuclear hydride tantalum(IV) compounds [(TaCpRX2)2(?-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(?5-C5Me5)X2}2(?-H)2] derivatives and the cyclic diazo reagent benzo[c]cinnoline afford the biphenyl-bridged (phenylimido)tantalum complexes [{Ta(?5-C5Me5)X2}2(?-NC6H4C6H4N)] along with the release of molecular hydrogen. When the compounds [(TaCpRX2)2(?-H)2] (CpR = ?5-C5H4SiMe3, ?5-C5HMe4; X = Cl, Br) were employed, we were able to trap the side-on-bound diazo derivatives [(TaCpRX)2{?-(?2,?2-NC6H4C6H4N)}] (CpR = ?5-C5H4SiMe3, ?5-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. © 2021 The Authors. Published by American Chemical Society.