The thermodynamically preferred conformations of the five-co-ordinate trigonal-bipyramidal complexes SbPh3Cl21 and BiPh3Cl2 2, determined via van der Waals energy calculations, have been found to be in good agreement with the corresponding correlated propeller arrangements which are observed in the solid state. However, similar calculations upon the corresponding diesters SbPh3(O2CR)2 3 and BiPh3(O2CR)2 4 [R = C(OH)Ph2 a or C6H4OH-o b] were at variance with the solid state, thereby indicating the participation of stabilising secondary bonding interactions between the metal centre and the carbonyl oxygen atom of the ester moiety. In accord with current Lewis acid–base bonding models, a strong correlation was found to exist between the pKa of the parent acid and the magnitude of the M⋯OC interaction. The complexes 3a,3b and 4a,4b were prepared in order to probe the effect of strong intramolecular hydrogen bonding upon the ability of ester ligands to stabilise sterically disfavoured conformations via
σnb donation. Single crystal X-ray analyses of 3a,3b and 4a demonstrate that although significant attenuation of the M⋯OC interaction is achieved via strong intramolecular hydrogen bonding, sterically disfavoured arrangements predominate in the solid state.
通过范德华能量计算确定的五配位三方双锥配合物 SbPh3Cl21 和 BiPh3Cl2 2 的热力学优选构象与在固态中观察到的相应相关螺旋桨排列非常一致。然而,对相应二酯 SbPh3(O2CR)2 3 和 BiPh3(O2CR)2 4 [R = C(OH)Ph2 a 或 C6H4OH-o b] 的类似计算与固态存在差异,从而表明稳定化的参与
金属中心和酯部分的羰基氧原子之间的二次键合相互作用。根据当前的
路易斯酸碱键合模型,发现母体酸的 pKa 与 M⋯OC 相互作用的强度之间存在很强的相关性。制备配合物 3a,3b 和 4a,4b 是为了探究强分子内氢键对酯
配体稳定空间不利构象的能力的影响
σnb 捐赠。 3a、3b 和 4a 的单晶 X 射线分析表明,尽管 M⋯OC 相互作用的显着减弱是通过强分子内氢键实现的,但空间不利的排列在固态中占主导地位。