This paper reports a density functional theory study of 3d transition-metal methoxide complexes with potentially redox-noninnocent pincer supporting ligands for methane C–H bond activation to form methanol (L_nM-OMe + CH₄ → L_nM–Me + CH₃OH). The three types of tridentate pincer ligands [terpyridine (NNN), bis(2-pyridyl)phenyl-C,N,N′ (NCN), and 2,6-bis(2-phenyl)pyridine-N,C,C′ (CNC)] and different first-row transition metals (M = Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) are used to elucidate the reaction mechanism as well as the effect of the metal identity on the thermodynamics and kinetics of a methane activation reaction. Spin-density analysis indicates that some of these systems, the NNN and NCN ligands, have redox-noninnocent character. A four-centered, kite-shaped transition state, σ-bond metathesis, or oxidative hydrogen migration has been found for methane activation for the complexes studied. Calculations suggest that the d electron count is a more significant factor than the metal formal charge in controlling the thermodynamics and kinetics of C–H activation and late 3d metal methoxides, with high d counts preferred. Notably, early-to-middle metals tend toward oxidative hydrogen migration and late metals undergo a pathway that is more akin to σ-bond metathesis, suggesting that metal methoxide complexes that favor σ-bond metathesis pathways for methane activation will yield lower barriers for C–H activation.

中文翻译：

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通过具有潜在的氧化还原-非无损钳形配体的3d金属甲醇络合物活化甲烷C-H：密度泛函理论研究

本文报道了密度泛函理论研究的3d过渡金属甲醇盐配合物，该配合物具有潜在的氧化还原-非无损钳位配体，可通过甲烷配体CH键活化形成甲醇（L _n M-OMe + CH ₄ →L _n M-Me + CH ₃ OH）。三种类型的三齿钳状配体[吡啶（NNN），双（2-吡啶基）苯基-C，N，N '（NCN）和2,6-双（2-苯基）吡啶-N，C，C'（CNC）]和不同的第一行过渡金属（M = Ti，V，Cr，Mn，Fe，Co，Ni和Cu）用于阐明反应机理以及金属身份对金属的影响。甲烷活化反应的热力学和动力学。自旋密度分析表明，其中一些系统，即NNN和NCN配体，具有氧化还原非清纯的特性。已经发现了四中心，风筝状的过渡态，σ键易位或氧化氢迁移，可用于所研究的配合物的甲烷活化。计算表明，在控制C–H活化和后期3d金属甲醇盐的热力学和动力学方面，d电子计数比金属形式电荷更重要，其中较高的d计数是可取的。尤其，