Transition Metal – Boron Complexes B n M : From Bowls ( n 5 8 – 14 ) to Tires ( n 5 14 )

Transition metal–boron complexes BnM have been predicted at density functional theory level to be molecular bowls (n 1⁄4 8–14) hosting a transition metal atom (M) inside or molecular tires (n 1⁄4 14) centered with a transition metal atom. Small Bn clusters prove to be effective inorganic ligands to all the VB–VIIIB transition metal elements in the periodic table. Density functional evidences obtained in this work strongly suggest that bowl-shaped fullerene analogues of Bn units exist in small BnM complexes and the bowl-to-tire structural transition occur to the first-row transition metal complexes BnM (M 1⁄4 Mn, Fe, Co) at n 1⁄4 14, a size obviously smaller than n 1⁄4 20 where the 2D-3D structural transition occurs to bare Bn. The half-sandwich-type B12Cr (C3v), full sandwich-type (B12)2Cr (D3d), bowl-shaped B14Fe (C2), and tire-shaped B14Fe (D7d) and B14Fe (C7v) are the most interesting prototypes to be targeted in future experiments. These BnM complexes may serve as building blocks to form extended boron-rich BnMm tubes or cages (m 2) or as structural units to be placed inside carbon nanotubes with suitable diameters. q 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1858–1865, 2006