Zhuo Hongying, Li Qingzhong
The Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Yantai University, Yantai 264005, People's Republic of China.
Phys Chem Chem Phys. 2015 Apr 14;17(14):9153-60. doi: 10.1039/c5cp00187k. Epub 2015 Mar 11.
An analogue of carbene, singlet silylene (H3P=N)2Si, was paired with the mono-substituted phosphines XH2Y (X = P, As, and Sb; Y = F, Cl, Br, and I) to form unconventional pnicogen-bonded complexes. All structures have Cs symmetry except the Sb complex, showing a deviation from this symmetry due to the coexistence of H···H interactions. The P and As complexes have different geometries from conventional pnicogen-bonded ones because the Y-X···Si line shows a large deviation from the molecular plane composed of two N atoms and one Si atom of (H3P=N)2Si. This deviation can be attributed to a new formation mechanism of the pnicogen bond due to the combined result of the LPSi→ BDX-Y and LPX→ LPSi orbital interactions. Generally, the pnicogen bond becomes stronger in the order of F < Cl < Br < I and weaker in the order of P > As > Sb, exhibiting an unexpected substitution effect and dependence on the nature of the pnicogen atom. These orders are inconsistent with the MEP on the X atom but can be better explained by the above orbital interactions. The Si···X interaction displays a character of covalent or partially covalent interaction, evidenced by the high interaction energy of -59.9 to -105.4 kJ mol(-1) as well as the negative energy density and the great charge transfer.
卡宾类似物单线态甲硅烯（H3P=N）2Si与单取代膦XH2Y（X = P、As和Sb；Y = F、Cl、Br和I）配对，形成非常规的氮族元素键合配合物。除了Sb配合物外，所有结构都具有Cs对称性，由于H···H相互作用的共存，Sb配合物显示出偏离这种对称性的情况。P和As配合物具有与传统氮族元素键合配合物不同的几何结构，因为Y-X···Si线与由（H3P=N）2Si的两个N原子和一个Si原子组成的分子平面有很大偏差。这种偏差可归因于LPSi→ BDX-Y和LPX→ LPSi轨道相互作用的综合结果导致的氮族元素键的新形成机制。一般来说，氮族元素键按F < Cl < Br < I的顺序变强，按P > As > Sb的顺序变弱，表现出意想不到的取代效应以及对氮族元素原子性质的依赖性。这些顺序与X原子上的分子静电势（MEP）不一致，但可以用上述轨道相互作用更好地解释。Si···X相互作用表现出共价或部分共价相互作用的特征，这由-59.9至-105.4 kJ mol(-1)的高相互作用能以及负能量密度和大量电荷转移所证明。
