Dinitrogen functionalization at a ditantalum center. Balancing N-2 displacement and N-2 functionalization in the reaction of coordinated N-2 with CS2

The reaction of carbon disulfide (CS2) with the side-on end-on dinitrogen complex ({[}NPNSi]Ta)(2)(-(1):(2)-N-2)(-H)(2) (1) (where {[}NPNSi] = {[}PhP(CH2SiMe2NPh)(2)]) has been studied and shown to generate two products, the ratio of which depends on the concentration of added carbon disulfide. At high concentrations of CS2, N-N bond cleavage and functionalization occur to generate a ditantalum complex with an isothiocyanato ligand N-bound to Ta along with bridging sulfido and nitrido moieties. At lower concentrations of CS2, less dinitrogen functionalization is observed; instead, N-2 is displaced and the CS2 molecule is completely disassembled to generate a ditantalum derivative with bridging methylene and two sulfide moieties. Kinetic and DFT studies have been performed and provide clues about the product ratio and mechanistic information and shed light on why N-2 functionalization is challenging.