Lewis Acidity and Reactivity of Transition Metal Oxo Complexes. A Comparative Density Functional Study of CH3ReO3, CH3TcO3, and Their Base Adducts
Lewis Acidity and Reactivity of Transition Metal Oxo Complexes. A Comparative Density Functional Study of CH3ReO3, CH3TcO3, and Their Base Adducts
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过渡金属氧配合物的路易斯酸度和反应性。
DOI：
10.1021/om9608317
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
N. Rösch
中科院分区：
文献类型：
--
作者：
S. Köstlmeier;V. Nasluzov;W. Herrmann;N. Rösch
本文对甲基三氧-铼及其较低同系物甲基三氧-锝的密度泛函进行了研究，研究了相对论效应对两种金属中心反应性的影响。为了量化中心金属原子的路易斯酸度，研究了以NH3为探针分子的加合物的形成。在Re - N距离为2.50 a （exp 2.40 - 2.50 a）时，甲基三氧-铼可形成稳定的碱加合物。对Tc配合物的计算（以及在非相对论理论水平上对Re配合物的计算）得出了更长的M - N距离（0.1 a）和更低的M - N键拉伸频率，这与相当小的结合能是一致的。根据计算的NH3加合物形成能和电荷分布的分析，可以得出结论：在MO3部分，Re是比Tc更强的刘易斯酸中心。MO3片段的极化率（硬度）由HOMO - LUMO分裂和M - O位移导数来量化。
A density functional investigation of methyltrioxo−rhenium and its lower homologue methyltrioxo−technetium studying the influence of relativistic effects on the reactivity of the two metal centers is presented. In order to quantify the Lewis acidity of the central metal atom, the adduct formation with NH3 as a probe molecule is investigated. Methyltrioxo−rhenium is calculated to form a stable base adduct at a Re−N distance of 2.50 A (exp 2.40−2.50 A). The calculations for the Tc complex (and for the Re complex at a nonrelativistic level of theory) yield longer M−N distances (by 0.1 A) and lower stretching frequencies for the M−N bond in line with the fairly small association energies. From the calculated NH3 adduct formation energies supported by an analysis of the charge distribution, one concludes that Re is a somewhat stronger Lewis acid center than Tc in the MO3 moiety. The polarizability (hardness) of the MO3 fragment is quantified by the HOMO−LUMO splitting as well as by the M−O displacement derivat...