Date: August 19, 2009
Creator: Harrold, Nicole D.; Waterman, Rory; Hillhouse, Gregory L. & Cundari, Thomas R., 1964-
Description: This article discusses 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=CPh2 (1; dtbpe = 1,2-bis(di-tert-butylphosphino)ethane) at ambient temperature to give the ketimines RN=CPh2 (2a, R = Mes; 2b, R = Ad) in high yield. Kinetic studies for the reaction of 1 with N3Ad yield activation parameters of ∆H‡ = +8(±1) kcal/mol and ∆S‡ = -44(±3) cal/(mol•K). Treatment of 1 with N2O at low temperature results in clean conversion to the benzophenone complex (dtbpe)Ni=NR (4a, R = Mes; 4b, R = Ad) react with N3Mes and N3Ad 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 N2 elimination to give the products. Calculated activation parameters for the reaction of (dhpe)Ni=CH2 (dhpe = 1,2-bis(dihydridophosphino)ethane) with N3Me compare well with the experimental values.
Contributing Partner: UNT College of Arts and Sciences