SIGMA-ELECTRONS IN SILANES AND PHOSPHANES - GEMINAL BOND INTERACTION, ANGLE STRAIN, AND DELOCALIZABILITY

Bond-to-bond delocalization of sigma-electrons in silanes and phosphanes was analyzed. Sigma-electrons in the Si-Si and P-P bonds were numerically shown to delocalize more than those in the C-C bonds and less than pi-electrons in C=C bonds. The delocalization between the geminal bonds is antibonding as was previously reported for the C-C bonds. As the bond angle is acute, the antibonding property increases in the silanes and decreases in the phosphanes. This implies that the three-membered ring is more strained in the silanes and less strained in the phosphanes. The concept of antibonding delocalization was substantiated. The correlation between the antibonding property of the geminal delocalization and angle strain was confirmed.