Comparison of hypoelectronic deltahedral ditechnetaboranes having eight to twelve vertices with their rhenium analogues: Examples of polyhedral surface metal–metal multiple bonds

Abstract

The lowest energy structures for the ditechnetaboranes Cp2Tc2Bn−2Hn−2 (n=8, 9, 10, 11, 12) are shown by density functional theory to be flattened oblate deltahedral structures analogous to their experimentally known rhenium analogues. These ditechnetaboranes typically have Tc–Tc distances ∼0.05Å shorter and Tc–Tc Wiberg bond indices 0.05 smaller than those in the analogous dirhenaboranes. Higher energy ditechnetaboranes are found with short Tc–Tc distances and closo or isocloso structures analogous to higher energy dirhenaboranes found in a previous theoretical study. These include 8-, 9-, 10-, and 12-vertex most spherical closo structures with formal TcTc polyhedral surface quadruple bonds as well as 10- and 11-vertex isocloso structures with formal TcTc polyhedral surface triple bonds.