Isocyanide versus nitrile ligands and methyl versus trifluoromethyl substituents in metal carbonyl chemistry

The relative energies of the nitrile and isocyanide metal carbonyl complexes LM(CO)n (L = RCN and RNC; R = CH3 and CF3; M = Cr, n = 5; M = Ni, n = 3; M = Fe, n = 4) have been compared using density functional theory. For the ligand pair CH3CN/CH3NC the acetonitrile complexes have consistently lower energies than the isomeric methyl isocyanide complexes. This relative energy order is reversed for the perfluorinated ligand pair CF3CN/CF3NC.