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

The reaction of (η5-C5H5)Co(PPh3)2 (1) with 1,3-bis(isopropyl)imidazol-2-ylidene (ImiPr2, 17) leads to the formation of (η5-C5H5)Co(PPh3)(ImiPr2) (5) in 69% yield. N-Heterocyclic carbene 17 also undergoes reaction with (η5-C5H5)Co(CO)2 (9) to give (η5-C5H5)Co(ImiPr2)(CO) (6) in 30% yield. The barrier to rotation about the Co−Ccarbene 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 (η5-C5H5)Co(ImiPr2)(SPh) (7), which is oxidized to the metallosulfone complex (η5-C5H5)Co(ImiPr2)(SO2Ph) (8). The solid-state structures of 5−8 were determined by X-ray crystallography. The structural and dynamic properties of 6, (η5-C5H5)Co(ImMe2)(CO) (ImMe2 = 1,3-dimethylimidazol-2-ylidene), and (η5-C5H5)Co(ImAr2)(CO) (ImAr2 = 1,3-dimesityl-2-ylidene) were examined by quantum chemistry calculations.(η⁵-环戊二烯基)双(三苯基膦)合钴[(η⁵-C₅H₅)Co(PPh₃)₂, 化合物1]与1,3-二异丙基咪唑-2-卡宾（氮杂环卡宾(N-Heterocyclic Carbene, NHC) ImiPr₂，化合物17）发生反应，以69%的产率得到(η⁵-环戊二烯基)(三苯基膦)(1,3-二异丙基咪唑-2-卡宾)合钴[(η⁵-C₅H₅)Co(PPh₃)(ImiPr₂), 化合物5]。氮杂环卡宾(N-Heterocyclic Carbene, NHC) 17同样可与(η⁵-环戊二烯基)二羰基合钴[(η⁵-C₅H₅)Co(CO)₂, 化合物9]反应，以30%的产率得到(η⁵-环戊二烯基)(1,3-二异丙基咪唑-2-卡宾)羰基合钴[(η⁵-C₅H₅)Co(ImiPr₂)(CO), 化合物6]。通过变温¹H核磁共振波谱法(variable-temperature ¹H NMR spectroscopy)与量子化学计算，测定了化合物6中钴-卡宾碳键的旋转能垒，二者结果分别为13.6 kcal/mol与13.3 kcal/mol。化合物5与二苯基二硫醚(PhSSPh)反应，生成顺磁性硫醇合钴配合物(η⁵-环戊二烯基)(1,3-二异丙基咪唑-2-卡宾)(苯硫基)合钴[(η⁵-C₅H₅)Co(ImiPr₂)(SPh), 化合物7]，该配合物可被氧化为金属磺酰基配合物(η⁵-环戊二烯基)(1,3-二异丙基咪唑-2-卡宾)(苯磺酰基)合钴[(η⁵-C₅H₅)Co(ImiPr₂)(SO₂Ph), 化合物8]。通过X射线晶体衍射法(X-ray crystallography)确定了化合物5至8的固态分子结构。通过量子化学计算，考察了化合物6、(η⁵-环戊二烯基)(1,3-二甲基咪唑-2-卡宾)羰基合钴[(η⁵-C₅H₅)Co(ImMe₂)(CO)，其中ImMe₂=1,3-二甲基咪唑-2-卡宾(1,3-dimethylimidazol-2-ylidene)]以及(η⁵-环戊二烯基)(1,3-二均三甲苯基咪唑-2-卡宾)羰基合钴[(η⁵-C₅H₅)Co(ImAr₂)(CO)，其中ImAr₂=1,3-二均三甲苯基咪唑-2-卡宾(1,3-dimesityl-2-ylidene)]的结构与动态性质。