Nitrile RC≡N Triple Bond Cleavage by a Dicopper Nitrite Complex with N ₂ Elimination and Formation of RCO ₂ – Carboxylate Ligands

This contribution showcases the complete scission of nitrile RC≡N bonds by [Cu 2 ( μ − κ 1 : κ 1 -O 2 N)DPFN][NTf 2 ] ( 1-NTf 2 ; DPFN = 2,7-bis(fluoro-di(2-pyridyl)methyl)-1,8-naphthyridine, NTf 2 – = N(SO 2 CF 3 ) 2 – ), with dinitrogen elimination. These reactions produce dicopper(I,I) carboxylate complexes, [Cu 2 ( μ − κ 1 : κ 1 -O 2 CR)DPFN][NTf 2 ] ( 4 R -NTf 2 ). A fleeting N -nitrosamide intermediate, [Cu 2 ( μ –N(NO)C(O)R)DPFN][NTf 2 ] ( 3 R -NTf 2 ), was detected by NMR spectroscopy and observed to decompose to the final products. While none of these novel N -nitrosamide-ligated dicopper complexes could be isolated due to their thermal instability, complex 3 Ph -NTf 2 was crystallographically characterized, and its bonding metrics were analyzed. Furthermore, kinetic studies on the in situ formation of 3 Ph -NTf 2 revealed first-order dependence on both 1-NTf 2 and PhCN. Quantum mechanical modeling was employed to develop a mechanistic scenario and elucidate other key intermediates in this unprecedented reaction. The nucleophilicity of the di-Cu(I) nitrite complex was further probed through its reaction with an aryl isocyanate to yield a diazotate complex, [Cu 2 ( μ − κ 1 : κ 1 -ONNXenyl)DPFN][NTf 2 ] ( 2-NTf 2 ; Xenyl = C 6 H 4 C 6 H 5 ), and CO 2 .