Collect. Czech. Chem. Commun. 1999, 64, 767-782

Connections Between 11B NMR Chemical Shifts and Electronic Structure in Metallaboranes. A Précis

Thomas P. Fehlner

Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, U.S.A.


An analysis of selected sets of metallaboranes in terms of a molecular orbital (MO) model of 11B chemical shift change is used to demonstrate the origin of transition metal effects on boron shifts for: (i) M-B edge protonation; (ii) replacement of direct B-B by M-B interactions; (iii) encapsulation of B in a metal cluster; (iv) change in metal identity; and (v) change in vertex coordination number. Metal effects on both filled and unfilled MO's are important but changes in the latter appear to dominate. Consequently, models based solely on filled orbital properties, e.g., electronic charge, are inadequate. A short review with 56 references.

Keywords: Boranes; Metallaboranes; NMR spectroscopy, 11B; Clusters; Molecular orbitals; Review.