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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Bond lengths in organic and metal-organic compounds revisited: X - H bond lengths from neutron diffraction data
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Bond lengths in organic and metal-organic compounds revisited: X - H bond lengths from neutron diffraction data

机译：再谈有机和金属有机化合物中的键长：中子衍射数据的X-H键长

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摘要

The number of structures in the Cambridge Structural Database (CSD) has increased by an order of magnitude since the preparation of two major compilations of standard bond lengths in mid-1985. It is now of interest to examine whether this huge increase in data availability has implications for the mean bond-length values published in the late 1980s. Those compilations reported mean X - H bond lengths derived from rather sparse information and for rather few chemical environments. During the intervening years, the number of neutron studies has also increased, although only by a factor of around 2.25, permitting a new analysis of X - H bond-length distributions for (a) organic X = C, N, O, B, and (b) a variety of terminal and homometallic bridging transition metal hydrides. New mean values are reported here and are compared with earlier results. These new overall means are also complemented by an analysis of X - H distances at lower temperatures (T ≤ 140 K), which indicates the general level of librational effects in X - H systems. The study also extends the range of chemical environments for which statistically acceptable mean X - H bond lengths can be obtained, although values from individual structures are also collated to further extend the chemical range of this compilation. Updated default neutron-normalization distances for use in hydrogen-bond and deformation-density studies are also proposed for C - H, N - H and O - H, and the low-temperature analysis provides specific values for certain chemical environments and hybridization states of X.
机译：自1985年中期编写标准键长的两个主要汇编以来，剑桥结构数据库（CSD）中的结构数量已增加了一个数量级。现在令人感兴趣的是，检查数据可用性的这种巨大增长是否对1980年代末发布的平均键长值有影响。这些汇编报告说，X-H键的平均长度来自稀疏信息，并且化学环境很少。在随后的几年中，中子研究的数量也有所增加，尽管仅增加了约2.25倍，这使得对（a）有机X = C，N，O，B， （b）各种末端和同金属桥接的过渡金属氢化物。在此报告新的平均值，并将其与早期结果进行比较。这些新的总体方法还可以通过在较低温度（T≤140 K）下分析X-H距离来补充，这表明X-H系统中的解放作用的一般水平。这项研究还扩大了化学环境的范围，在该环境中可以获得统计学上可接受的平均X-H键长度，尽管还整理了各个结构的值，以进一步扩大该化学信息的范围。还提出了用于C-H，N-H和O-H的氢键和变形密度研究中使用的更新的默认中子标准化距离，低温分析为某些化学环境和杂化状态提供了特定的值。 X。

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