abstract36
Inorg. Chem., 40 (8), 1790 -1801, 2001. 10.1021/ic000844j S0020-1669(00)00844-2
Web Release Date: March 3, 2001
Copyright © 2001 American Chemical Society
Empirical and ab Initio Energy/Architectural Patterns for 73 nido-6<V>-Carborane Isomers, from B6H9– to C4B2H6#
Matthias Hofmann, Mark A. Fox, Robert Greatrex, Paul v. R. Schleyer, and Robert E. Williams*
Loker Hydrocarbon Research Institute, University of Southern California, University Park, Los Angeles, California 90089-1661, Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany, Department of Chemistry, Durham University Science Laboratories, South Road Durham, DH1 3LE, U.K., School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K., Center for Computational Quantum Chemistry, University of Georgia, 1004 Cedar Street, Athens, Georgia 30602, and Institut für Organische Chemie der Universität Erlangen-Nürnberg, Henkestrasse 42, D-91054 Erlangen, Germany
Received July 26, 2000
Abstract:
Qualitative rules governing carbon and bridge-hydrogen placement permit the prediction of the most stable isomeric structures for the various carboranes. Seventy-three isomeric boron hydride and carborane structures, from B6H9– to C4B2H6, were computed at the ab initio MP2(fc)/6-31G* level to determine their relative stabilities quantitatively. Specific architectural features, recognized to be unfavorable, were assigned “energy penalty” values that allow the projection of comprehensive thermodynamic stability values via a simple additivity procedure. These values match the ab initio results with surprising precision. Our study includes Siebert’s nido-2,3,5-C3B3H7 and Wrackmeyer’s nido-2,4-C2B4H8 nido-6<V> carboranes, which contain “unusual” CH-B-bridge hydrogens.