Structures and stabilities of heteroatom-substituted disilenes and related compounds: Four-center π systems

The geometries of (H₂X)HE=EH(XH₂), (H₂X)HE=EH(XH₂)²⁺, and HX=EHHE=XH (E = Si, C; X = Al, B, P, N) have been studied using ab initio molecular orbital calculations. Relative stabilities of the stereoisomers of the four-center π systems were explained by the orbital-phase continuity of the terminal atoms. Isodesmic reaction energies show that π conjugation is effective for stabilization of compounds with AlH₂ and BH₂ substituents on the unsaturated silicon, and therefore, aluminum- and boron-substituted disilenes can be potential synthetic targets.