The change in sign of the interaction force constant between element-hydrogen stretching modes of trans-dihydrides of the d block and p block elements is analyzed for the first time. As the transition metal M approaches group 12, the higher energy symmetric trans-H–M–H vibration ν_sym approaches the energy of the antisymmetric vibration ν_asym. Crossing to group 13 elements E, the trans-H–E–H vibration ν_sym increasingly drops below ν_asym. This reversal is attributed to the d orbital that participates in the H–M–H bonding but is nonbonding in the H–E–H compounds. DFT calculations are used to probe the energetics of isoelectronic triatomic [H–M–H]ⁿ⁺ and [H–E–H]ⁿ⁻ to reveal this trend and also to demonstrate that the magnitude of these interactions (ν_gap) increases down groups 11, 12, and 14 but remains fairly constant for group 13. They are also used to show that this reversal is seen in the transition state for hydride transfer to CO₂ from the model compounds trans-NiH₂(porphyrin) and trans-EH₂(porphyrin), E = Si and Ge in their singlet states.

中文翻译：

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反式元素-氢键：过渡金属和主族元素之间的显着区别

首次分析了d嵌段和p嵌段元素的反式二氢化物的元素-氢拉伸模式之间相互作用力常数的符号变化。随着过渡金属 M 接近第 12 族，更高能量的对称trans -H–M–H 振动 ν _sym接近反对称振动 ν _asym的能量。穿越到第 13 组元素 E，反式-H–E–H 振动 ν _sym逐渐下降到 ν _asym之下。这种反转归因于参与 H-M-H 键合但在 H-E-H 化合物中不成键的 d 轨道。DFT 计算用于探测等电子三原子 [H–M–H] ⁿ的能量学⁺和 [H–E–H] ^{n −}揭示这一趋势，并证明这些相互作用的幅度 (ν _gap ) 在第 11、12 和 14 组向下增加，但在第 13 组中保持相当稳定。它们也被使用为了表明在氢化物从模型化合物反式-NiH ₂（卟啉）和反式-EH ₂（卟啉）转移到CO ₂的过渡态中看到这种逆转，E = Si 和Ge 处于单线态。