Cobalt 1,3-diisopropyl-1 H -imidazol-2-ylidene complexes: Synthesis, solid-state structures, and quantum chemistry calculations

摘要

The reaction of (η~5-C_5H_5)Co(PPh _3)_2 (1) with 1,3-bis(isopropyl)imidazol-2-ylidene (Im ~iPr_2, 17) leads to the formation of (η~5- C_5H_5)Co(PPh_3)(Im~iPr_2) (5) in 69% yield. N-Heterocyclic carbene 17 also undergoes reaction with (η~5-C_5H_5)Co(CO)_2 (9) to give (η~5-C_5H_5)Co(Im~iPr _2)(CO) (6) in 30% yield. The barrier to rotation about the Co-C ~(carbene) bond in 6 has been determined by variable-temperature ~1H NMR spectroscopy (13.6 kcal/mol) and by computation (13.3 kcal/mol). Complex 5 undergoes reaction with PhSSPh to give the paramagnetic thiolato complex (η~5-C_5H_5)Co(Im ~iPr_2)(SPh) (7), which is oxidized to the metallosulfone complex (η~5-C_5H_5)Co(Im~iPr _2)(SO_2Ph) (8). The solid-state structures of 5-8 were determined by X-ray crystallography. The structural and dynamic properties of 6, (η~5-C_5H_5)Co(ImMe_2)(CO) (ImMe_2 = 1,3-dimethylimidazol-2-ylidene), and (η~5- C_5H_5)Co(ImAr_2)(CO) (ImAr_2 = 1,3-dimesityl-2-ylidene) were examined by quantum chemistry calculations.