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 (Ar[<i>t</i>-Bu]N)<sub>3</sub>Mo(NC(X)Ph), where Ar = 3,5-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub> and X = SC<sub>6</sub>F<sub>5</sub>, SeC<sub>6</sub>F<sub>5</sub>, or O<sub>2</sub>CPh, are formally derived from addition of the carbene fragment [<b>:</b>C(X)Ph] to the terminal nitrido molybdenum(VI) complex (Ar[<i>t</i>-Bu]N)<sub>3</sub>Mo≡N in which the nitrido nitrogen atom is installed by scission of molecular nitrogen. Herein the pivotal (Ar[<i>t</i>-Bu]N)<sub>3</sub>Mo(NC(X)Ph) complexes are obtained through independent synthesis, and their propensity to undergo beta-X elimination, i.e., conversion to (Ar[<i>t</i>-Bu]N)<sub>3</sub>MoX + PhC≡N, is investigated. Radical C−X bond formation reactions ensue when benzonitrile is complexed to the three-coordinate molybdenum(III) complex (Ar[<i>t</i>-Bu]N)<sub>3</sub>Mo and then treated with 0.5 equiv of X<sub>2</sub>, leading to facile assembly of the key (Ar[<i>t</i>-Bu]N)<sub>3</sub>Mo(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 = O<sub>2</sub>CPh, and the reaction represents an attractive component of an overall synthetic cycle for incorporation of dinitrogen-derived nitrogen atoms into organic nitrile (R−C≡N) molecules.