Unifying chemical bonding models for boranes

Abstract

We demonstrate, based on first-principles calculations, that chemical bonding in deltahedral boron hydrides, BnHn���{�z also known as closo boranes, can be understood within the three-center two-electron (3c2e) bonding model in line with other families of boranes. We show that bonding in the triangular lattice of BnHn���{ cages can be described by delocalized resonant 3c2e bonding of �� electrons, giving rise to ���naromaticity. Such delocalization, in the case of B12H122�{, leads to well-defined electronic shell structure. We also find that the reason for all the BnHn���{ to be dianions can be attributed to the reduction of boron coordination number in the deltahedral cage structure from that of boron sheet with triangular lattice.