Coupling of fluoroborylene ligands in manganese carbonyl chemistry to give a difluorodiborene ligand

Abstract

The geometries and energetics of the binuclear fluoroborylene manganese carbonyls Mn₂(BF)₂(CO)_n (n = 8, 7, 6) have been investigated using density functional theory. Coupling of two fluoroborylene ligands to give a bridging difluorodiborene μ-B₂F₂ ligand with a relatively long ∼1.9 Å B–B bond has been observed in two of the three lowest energy Mn₂(BF)₂(CO)₇ structures as well as the lowest energy Mn₂(BF)₂(CO)₆ structure. Higher energy Mn₂(BF)₂(CO)₆ structures have two separate bridging BF groups and short MnMn distances of ∼2.3 Å suggesting the formal triple bond required by the 18-electron rule.