Dinitrogen Cleavage and Multicoupling with Isocyanides in a Dititanium Dihydride Framework.

Dinitrogen (N) activation and functionalization through N-N bond cleavage and N-C bond formation are of great interest and importance but remain highly challenging. We report here for the first time N cleavage and selective multicoupling with isocyanides in a dititanium dihydride framework. The reaction of a dinitrogen dititanium dihydride complex [{(PNP)Ti}(μ-η:η-N)(μ-H)] () with an excess (four or more equivalents) of -methoxyphenyl isocyanide at room temperature gave a novel amidoamidinatoguanidinate complex [(PNP)Ti{NC(═NR)NC(═NR)CHNR}Ti(PNP)(CNR)] (, PNP = 4,5-bis(diisopropylphosphino)-2,7,9,9-tetramethyl-9-acridin-10-ide; R = -MeOCH) through N splitting and coupling with three isocyanide molecules. When 1 equiv of -methoxyphenyl isocyanide was used to react with at -30 °C, the hydrogenation of the isocyanide unit by the two hydride ligands in took place, affording an amidomethylene-bridged dititanium dinitrogen complex [{(PNP)Ti}(μ-η:η-N){μ-η:η-CHN(-MeOCH)}] (), which upon reaction with another equivalent of -methoxyphenyl isocyanide at room temperature gave an amidomethylene/nitrido/carbodiimido complex [(PNP)Ti(N═C═NR)(μ-N)(μ-η:η-CHNR)Ti(PNP)] () through N cleavage and N═C bond formation. Further reaction of with 1 equiv of -methoxyphenyl isocyanide led to an unprecedented four-component (carbodiimido, nitrido, isocyanide, and amidomethylene) coupling, yielding an amidoamidinatoguanidinate complex [{(PNP)Ti}{NC(═NR)NC(═NR)CHNR}] (), which on reaction with another equivalent of -methoxyphenyl isocyanide afforded the isocyanide-coordinated analogue . The reaction of with 2-naphthyl isocyanide also took place in a similar multicoupling fashion. Moreover, the cross-coupling reactions of the -methoxyphenyl isocyanide-derived amidomethylene/nitrido/carbodiimido complex with 2-naphthyl isocyanide, cyclohexyl isocyanide, and -butyl isocyanide were also achieved, which afforded the corresponding amidoamidinatoguanidinate products consisting of two different isocyanides. Density functional theory (DFT) calculations further elucidated the mechanistic details.