The reactivity of the reduced Zr/Co and Ti/Co complexes (THF)Zr(MesNPⁱPr₂)₃CoN₂ (1, Mes = 2,4,6-trimethylphenyl) and (THF)Ti(XylNPⁱPr₂)₃CoN₂ (7, Xyl = 3,5-dimethylphenyl) toward diaryl ketones is explored in an effort to gain mechanistic insight into C═O bond cleavage processes. Complex 1 reacts with 4,4′-dimethoxybenzophenone to generate ((p-OMeC₆H₄)₂CO)Zr(MesNPⁱPr₂)₃CoN₂ (2), which exists as a mixture of valence tautomers in solution that interconvert via electron transfer from Co^–I to the Zr-bound ketone in 2^S to form a Zr-bound ketyl radical in 2^T. The geometry of 2 in the solid state is most consistent with the singlet ketone adduct tautomer 2^S. Upon removal of the Co-bound N₂ under vacuum, complex 2 cleanly coverts to the μ-oxo carbene product (η²-MesNPⁱPr₂)Zr(MesNPⁱPr₂)₂(μ-O)Co═C(C₆H₄p-OMe)₂ (5) at room temperature in solution. A diamagnetic intermediate, tentatively assigned as ketone-bridged species (η²-MesNPⁱPr₂)Zr(MesNPⁱPr₂)₂Co(μ₂,η¹η²-OC(p-OMeC₆H₄)₂) (6), is observed spectroscopically during the transformation of 1 to 5. Similar reactions between the Ti/Co analogue 7 and diaryl ketones reveal no evidence for electron-transfer to form triplet ketyl radical species. Complex 7 reacts with 4,4′-dimethoxybenzophenone to afford diamagnetic ((p-OMeC₆H₄)₂CO)Ti(XylNPⁱPr₂)₃CoN₂ (8). In contrast, addition of benzophenone to 7 under N₂ generates a mixture of (η²-XylNPⁱPr₂)Ti(XylNPⁱPr₂)₂Co(η²-OCPh₂) (9) and (Ph₂CO)Ti(XylNPⁱPr₂)₃CoN₂ (10) in solution, and C₃-symmetric 10 is found to be favored in the solid state. Complex 9 can be generated exclusively and isolated in the absence of N₂. Ti/Co complexes 8–10 are thermally stable and do not undergo C═O bond cleavage even at elevated temperature, in stark contrast to their Zr/Co congeners.

中文翻译：

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异双金属Zr / Co和Ti / Co三（膦酰胺）配合物对酮C═O键活化过程的研究

还原的Zr / Co和Ti / Co络合物（THF）Zr（MesNP ⁱ Pr ₂）₃ CoN ₂（1，Mes = 2,4,6-三甲基苯基）和（THF）Ti（XylNP ⁱ Pr ₂）的反应性探索了对二芳基酮的₃ CoN ₂（7，Xyl = 3,5-二甲基苯基），以期获得对C═O键断裂过程的机械理解。配合物1与4,4'-二甲氧基二苯甲酮反应生成（（p -OMeC ₆ H ₄）₂ CO）Zr（MesNP ⁱ Pr ₂）₃ CoN₂（2），它是价互变异构体在溶液中的混合物，它们通过电子转移从Co ^–I转移到2 ^S中与Zr结合的酮上，从而在2 ^T中形成Zr结合的酮基。固态的2的几何形状与单线态酮加合物互变异构体2 ^S最一致。在移除共同结合的N-的₂在真空下，复杂的2个干净覆羽到μ氧代卡宾产物（η ² -MesNP^我镨₂基）Zr（MesNP^我镨₂）₂（μ-O）Co═C（C在室温下在溶液中为₆ H ₄ p -OMe）₂（5）。反磁性中间，暂定为酮桥接物种（η ² -MesNP^我镨₂基）Zr（MesNP^我镨₂）₂的Co（μ ₂，η ¹ η ² -OC（p -OMeC ₆ ħ ₄）₂）（6），是在1到5的转变过程中用光谱法观察到的。Ti / Co类似物7之间的相似反应二芳基酮和二芳基酮未显示出电子转移形成三重态酮基自由基的证据。配合物7与4，4'-二甲氧基二苯甲酮反应，得到抗磁性的（（p -OMeC ₆ H ₄）₂ CO）Ti（XylNP ⁱ Pr ₂）₃ CoN ₂（8）。相反，除了以二苯甲酮的7氮气下₂产生的混合物（η ² -XylNP^我镨₂）的Ti（XylNP^我镨₂）₂的Co（η ² -OCPh ₂）（9）和（Ph ₂ CO）Ti（XylNP ⁱ Pr ₂）₃ CoN ₂（10）的溶液中，发现C ₃对称的10呈固态。可以仅在没有N ₂的情况下生成并分离复合物9。钛/钴络合物8 - 10是热稳定的，甚至在升高的温度下不发生C = O键断裂，形成鲜明对比，其的Zr / Co的同类物。