Group-Transfer Reactions of Nickel−Carbene and −Nitrene Complexes with Organoazides and Nitrous Oxide that Form New C═N, C═O, and N═N Bonds

Abstract

1-Adamantyl- and mesitylazide react with (dtbpe)Ni=CPh(2) (1; dtbpe = 1,2-bis(di-tert-butylphosphino)ethane) at ambient temperature to give the ketimines RN=CPh(2) (2a, R = Mes; 2b, R = Ad) in high yield. Kinetic studies for the reaction of 1 with N(3)Ad yield activation parameters of DeltaH(double dagger) = +8(+/-1) kcal/mol and DeltaS(double dagger) = -44(+/-3) cal/(mol.K). Treatment of 1 with N(2)O at low temperature results in clean conversion to the benzophenone complex (dtbpe)Ni(eta(2)-OCPh(2)) (5) upon elimination of N(2). The nickel-imido complexes (dtbpe)Ni=NR (4a, R = Mes; 4b, R = Ad) react with N(3)Mes and N(3)Ad at ambient temperature to give the diazenes RN=NR (6a, R = Mes; 6b, R = Ad) in good yield. B3LYP/6-311+G(d) calculations support a mechanism for all three reactions that features 1,3-dipolar cycloaddition to give five-membered ring (Huisgen) intermediates, followed by N(2) elimination to give the products. Calculated activation parameters for the reaction of (dhpe)Ni=CH(2) (dhpe = 1,2-bis(dihydridophosphino)ethane) with N(3)Me compare well with the experimental values.