Cobalt 1,3-Diisopropyl-1H-imidazol-2-ylidene Complexes: Synthesis, Solid-State Structures, and Quantum Chemistry Calculations

[Image: see text] The reaction of (η(5)-C(5)H(5))Co(PPh(3))(2) (1) with 1,3-bis(isopropyl)imidazol-2-ylidene (Im(i)Pr(2), 17) leads to the formation of (η(5)-C(5)H(5))Co(PPh(3))(Im(i)Pr(2)) (5) in 69% yield. N-Heterocyclic carbene 17 also undergoes reaction with (η(5)-C(5)H(5))Co(CO)(2) (9) to give (η(5)-C(5)H(5))Co(Im(i)Pr(2))(CO) (6) in 30% yield. The barrier to rotation about the Co−C(carbene) bond in 6 has been determined by variable-temperature (1)H 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(5)H(5))Co(Im(i)Pr(2))(SPh) (7), which is oxidized to the metallosulfone complex (η(5)-C(5)H(5))Co(Im(i)Pr(2))(SO(2)Ph) (8). The solid-state structures of 5−8 were determined by X-ray crystallography. The structural and dynamic properties of 6, (η(5)-C(5)H(5))Co(ImMe(2))(CO) (ImMe(2) = 1,3-dimethylimidazol-2-ylidene), and (η(5)-C(5)H(5))Co(ImAr(2))(CO) (ImAr(2) = 1,3-dimesityl-2-ylidene) were examined by quantum chemistry calculations.