Planar Four-Coordinate Boron: A Single, Flat Boron Atom as a Ligand for Four Metals

摘要

One of the consequences of valence-shell electron pair repulsion (VSEPR) theory is that when the main-group elements nitrogen, carbon, and boron are four-coordinate (that is, NR4~+, CR4, or BR4~-), the absence of extra electrons at the central atom means the four substituents attempt to get as far away from each other as possible, thus forming a tetrahedron.In the face of an overwhelming majority of molecules with tetrahedral carbon atoms, researchers have long taken a theoretical and synthetic interest in preparing compounds with planar tetracoordinate carbon atoms—a seemingly unlikely geometrical extreme.