Here it is demonstrated that there is a linear relationship between the terminal 3d metal hydride stretching wavenumber ν_MH and the metal hydride distance d_MH reported to date: ν_MH ∼ (−1.05d_MH + 3.35) × 10³ cm^–1. That is, upon moving from Group 3 to Group 10 metals in complexes and binary molecules, ν_MH (cm^–1) increases as the metal–hydrogen distance d_MH (Å) decreases as determined by X-ray diffraction, molecular spectroscopy, and, in one case, neutron diffraction. This trend contrasts with the relatively constant bond dissociation free energy (BDFE) of the diamagnetic complexes and the usually smaller BDFE (by as much as −20 kcal/mol) of paramagnetic ones, thus showing that there is no correlation between either ν_MH or its force constant with the BDFE. If a positive charge is added to the complex by metal-ion oxidation, ν_MH may increase or decrease depending on the coordination number and spin state of the complex.

中文翻译：

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过渡金属氢化物键长与拉伸波数之间的关系


这里证明，末端 3d 金属氢化物拉伸波数 ν_MH 与迄今为止报道的金属氢化物距离 _{d MH} 之间存在线性关系：ν_MH ∼ （−1.05d_MH + 3.35） × 10³ cm^–1。也就是说，当复合物和二元分子中的金属从第 3 族移动到第 10 族金属时，ν_MH （cm^–1） 随着金属-氢距离 d_MH （Å） 的减小而增加，这是由 X 射线衍射、分子光谱学确定的，在一种情况下，中子衍射是确定的。这种趋势与抗磁性配合物相对恒定的键解离自由能 （BDFE） 和顺磁性配合物通常较小的 BDFE（高达 -20 kcal/mol）形成鲜明对比，从而表明 ν_MH 或其力常数与 BDFE 之间没有相关性。如果通过金属离子氧化向配合物中添加正电荷，则 ν_MH 可能会增加或减少，具体取决于配合物的配位数和自旋态。