Coupling of Terminal Alkynes and Isonitriles by Organoactinide Complexes: Scope and Mechanistic Insights

The coupling reaction of terminal alkynes with several isonitriles, catalyzed by the neutral organoactinide complexes Cp* 2 AnMe 2 (Cp* = C 5 Me 5, An = Th, U) or the cationic complex [(Et 2 N) 3 U][BPh 4 ], yielded substituted α,β-acetylenic aldimines, in good to excellent yields. The reaction proceeded via a 1,1-insertion of the isonitrile carbon into a metal−acetylide bond, followed by a protonolysis by the acidic proton of the terminal alkyne. Additional insertion products were obtained by altering the catalyst and the reactant ratios. A plausible mechanism for the catalytic reaction is also presented, based on kinetics measurements and thermodynamic studies of the coupling reaction with Cp* 2 ThMe 2 or [(Et 2 N) 3 U][BPh 4 ] as catalysts. The reaction is first-order in catalyst and isonitrile and zero-order in alkyne.