Reversible Base Coordination to a Disilene

摘要

During the last few decades, alkene and alkyne analogues of the heavier Group 14 elements have attracted considerable interest. Their isolation as stable derivatives has become possible by the use of carefully designed bulky substituents that provide kinetic (and to some extent thermodynamic) stabilization. The considerable differences in structure, bonding, and reactivity of such compounds in comparison to the carbon-based species have prompted various experimental and theoretical studies. By and large, the lower electronegativity of heavier elements and the increasing spatial extension of their valence electron shells are responsible for many of these differences. One of several rationalizations for structure and reactivity of such doubly and triply bonded species is based on zwitterionic (Ib and IIb in Scheme 1) and diradical contributions (Ic and IIc in Scheme 1) to the ground state structures, which illustrate both the weakness and the trans-bent structure of heavier multiple bonds. Such contributions are, however, more prominent in compounds of germanium, tin, and lead, and less pronounced in compounds of silicon.