Benzonitrile extrusion from molybdenum(IV) ketimide complexes obtained via radical C-E (E = O, S, Se) bond formation: toward a new nitrogen atom transfer reaction

Beta-elimination is explored as a possible means of nitrogen-atom transfer into organic molecules. Molybdenum(IV) ketimide complexes of formula (Art-Bu]N)3Mo(N=C(X)Ph), where Ar = 3,5-Me2C6H3 and X = SC6F5, SeC6F5, or O2CPh, are formally derived from addition of the carbene fragment :C(X)Ph] to the terminal nitrido molybdenum(VI) complex (Art-Bu]N)3Mo identical with N in which the nitrido nitrogen atom is installed by scission of molecular nitrogen. Herein the pivotal (Art-Bu]N)3Mo(N=C(X)Ph) complexes are obtained through independent synthesis, and their propensity to undergo beta-X elimination, i.e., conversion to (Art-Bu]N)3MoX + PhC identical with N, is investigated. Radical C-X bond formation reactions ensue when benzonitrile is complexed to the three-coordinate molybdenum(III) complex (Art-Bu]N)3Mo and then treated with 0.5 equiv of X2, leading to facile assembly of the key (Art-Bu]N)3Mo(N=C(X)Ph) molecules. Treated herein are synthetic, structural, thermochemical, and kinetic aspects of (i) the radical C-X bond formation and (ii) the ensuing beta-X elimination processes. Beta-X elimination is found to be especially facile for X = O2CPh, and the reaction represents an attractive component of an overall synthetic cycle for incorporation of dinitrogen-derived nitrogen atoms into organic nitrile (R-C identical with N) molecules.