The <i>isocloso</i> capped pentagonal bipyramid versus the <i>closo</i> bisdisphenoid in hypoelectronic eight‐vertex metallaboranes having 16 skeletal electrons

AbstractThe lowest energy structures for all of the eight‐vertex [M]CB6H7 {[M] = CpFe, CpRu. Co(CO)2, Rh(CO)2, (Me3P)2Fe(H), (Me3P)2Ru(H)}, [M]C2B5H7 {[M] = CpMn, CpRe, Cr(CO)3, Mo(CO)3}, and [M]2C2B4H6 [M] = CpFe, CpRu systems having 16 skeletal electrons were found by density functional theory to be capped pentagonal bipyramids providing a degree 6 vertex for a metal atom. Thus the capped pentagonal bipyramid plays a similar role for eight‐vertex metallaboranes with 16 skeletal electrons as the isocloso deltahedra play in 9‐ and 10‐vertex metallaboranes with 18 and 20 skeletal electrons, respectively. Furthermore, in all of these metallaborane systems the closo bisdisphenoidal structures were always found to be higher energy structures than their capped pentagonal bipyramidal isomers. For the bimetallic systems Cp2M2C2B4H6 M = Fe, Ru even higher energy hexagonal bipyramid structures with degree 6 vertices for both metal atoms were also found.