Neutral Zr^IV and Hf^IV alkyl/amido complexes stabilized by a tridentate N ligand that contains a “rolling” heterodentate benzoimidazole fragment have been prepared and characterized. The ultimate nature of the ligand denticity, the electronic properties of the ligand binding pocket and the metal coordination environment are controlled by the protection/deprotection of the benzoimidazole NH group. The metal precursor used [M^IV(Bn)₄ or M^IV(NMe₂)₄] also has an influence on the final coordination sphere of the complex; indeed, a permanent central pyridine dearomatization occurs in the presence of dimethylamido ancillary groups. DFT calculations on the real system have been used to elucidate the mechanism. Selected alkyl species from this series have been scrutinized for the tandem hydrosilylation of CO₂ to CH₄ in combination with the strong Lewis acid B(C₆F₅)₃ using a variety of hydrosilanes. A positive effect of the hardness modification of the ligand donor atom set is observed in the catalytic outcomes. Indeed, κ³{N⁻,N,N⁻}Zr^IV(Bn)₂ catalyzes the process to methane selectively with a turnover frequency as high as 272 h⁻¹ (at 96 % substrate conversion) almost twice as much as that claimed for the benchmark κ³{O⁻,O,O⁻}Zr^IV(Bn)₂ complex under similar experimental conditions.

中文翻译：

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苯并咪唑-吡啶基酰胺基锆和Ha烷基络合物作为均相催化剂将二氧化碳串联硅烷化为甲烷

已制备并表征了由三齿N配体稳定的中性Zr ^IV和Hf ^IV烷基/酰胺配合物，该三齿N配体包含“滚动”异齿苯并咪唑片段。配体密度的最终性质，配体结合口袋的电子性能和金属配位环境由苯并咪唑NH基团的保护/脱保护来控制。使用的金属前体[M ^IV（Bn）₄或M ^IV（NMe ₂）₄]也影响了综合大楼的最终协调范围；实际上，在二甲基酰胺基辅助基团的存在下，永久性的中央吡啶脱芳香化作用发生。实际系统上的DFT计算已用于阐明该机制。从这一系列选择的烷基物种经过仔细审查并CO的氢化硅烷化串联₂至CH ₄结合的强路易斯酸B（C ₆ ˚F ₅）₃使用各种氢硅烷的。在催化结果中观察到配体供体原子组的硬度改性的积极作用。事实上，κ ³ { ñ ^- ，Ñ，ñ ^-}锆^IV（BN）_2个催化的过程中甲烷选择性地与转换频率高达272ħ ^-1（在96％的底物转化）几乎两倍，所要求保护为基准κ ³ { ø ^- ，Ö，ö ^- }锆^IV（BN）₂类似的实验条件下复合物。