Mohri F
Institute for Fundamental Chemistry, 34-4 Takano-Nishihiraki-cho, Sakyoku, Kyoto 606-8103, Japan.
Acta Crystallogr B. 2000 Aug;56(Pt 4):626-38. doi: 10.1107/s0108768100005401.
A new empirical relationship s = s0(R0 - lambda)3/(R - lambda)3 between bond distances and bond valences is proposed, where s is the bond valence for the bond distance R, s0 is the reference bond valence for the reference system with the reference bond distance R0 and lambda is the sum of the cation radii of bonding atoms defined by Pauling. Since lambda is the size of the inner electron region, R - lambda represents the valence electron region between bonding atoms. The new relationship was derived based on the following three hypotheses. (i) The number of electrons (p) in the volumes of (R - lambda)3 in a coordination polyhedron are equal, even if the bond distances are not equal to each other. (ii) The average electron density p/(R - lambda)3 is a measure of covalent bond strength. (iii) The sum of the average electron densities around the central atom is conserved, even if the coordination number changes. The new relationship is applicable not only to polyhedra with one type of ligand atom, but also to polyhedra with two or more types of ligand atoms and explains why the Brown-Shannon formula [Brown & Shannon (1973). Acta Cryst. A29, 266-282] and the Brown-Altermatt formula [Brown & Altermatt (1985). Acta Cryst. B41, 244-247] work well. The new relationship was applied to a penta-coordinated silicon compound, strong hydrogen-bond systems and some organic compounds with carbon-carbon bonds.
提出了一种新的键长与键价之间的经验关系(s = s_0(R_0 - \lambda)^3/(R - \lambda)^3)，其中(s)是键长为(R)时的键价，(s_0)是键长为(R_0)的参考体系的参考键价，(\lambda)是由鲍林定义的成键原子的阳离子半径之和。由于(\lambda)是内层电子区域的大小，(R - \lambda)代表成键原子之间的价电子区域。新关系基于以下三个假设推导得出。(i) 即使键长彼此不相等，配位多面体中体积为((R - \lambda)^3)的电子数((p))也是相等的。(ii) 平均电子密度(p/(R - \lambda)^3)是共价键强度的一种度量。(iii) 即使配位数改变，中心原子周围平均电子密度的总和也是守恒的。新关系不仅适用于具有一种配体原子的多面体，也适用于具有两种或更多种配体原子的多面体，并解释了为什么布朗 - 香农公式[Brown & Shannon (1973). Acta Cryst. A29, 266 - 282]和布朗 - 阿尔特马特公式[Brown & Altermatt (1985). Acta Cryst. B41, 244 - 247]效果良好。新关系被应用于一种五配位硅化合物、强氢键体系以及一些含有碳 - 碳键的有机化合物。
