Molybdatricarbaboranes as examples of isocloso metallaborane deltahedra with three carbon vertices.

Density functional theory shows that the lowest energy CpMoC3B n−4H n−1 ( n = 8, 9, 10, 11) structures are based on isocloso or similar deltahedra with the molybdenum atom at a degree 6 vertex. Such deltahedra include the capped pentagonal bipyramid for the 8-vertex system. Among such geometries the lowest energy structures have the carbon atoms at the lowest degree vertices (typically degree 4 vertices), no pairs of adjacent carbon atoms (i.e., no C-C edges), and the maximum number of Mo-C edges. Optimizing these factors favoring low-energy CpMoC3B n−4H n−1 ( n = 8, 9, 10, 11) structures leads to a unique lowest energy structure lying more than 10 kcal/mol below the next lowest energy structure for the 8-, 10-, and 11-vertex systems. However, the 9-vertex CpMoC3B5H8 system has three structures within 8 kcal/mol including a structure based on the closo tricapped trigonal prism rather than the isocloso 9-vertex deltahedron. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]