Two octahedral σ-borane metal (MnI and RuII) complexes containing a tripod κ3N,H,H-ligand: Synthesis, structural characterization, and theoretical topological study of the charge density

Theoretical electron density (QTAIM) studies in the gas-phase have shown that the attachment of the BH3 group to the metal atom in complexes [Mn(κ3N,H,H-iPr2bzamBH3)(CO)3] (1) and [Ru(η5-C5Me5)(κ3N,H,H-iPr2bzamBH3)] (2) (HiPr2bzamBH3 = N-trihydridoborane-N,N′-bis(isopropyl) benzamidine) is symmetric in the latter but asymmetric in the former, and involves two B–H–metal interactions that are intermediate between κ1H (Shimoi type) and κ2H,B (agostic type). The herein reported results, coupled to previous ones on related complexes having a similar tripod κ3N,H,H-borane ligand, show that the bonding similarities and differences within each particular M(μ-H)2B moiety are not related to the type of metal atom, nor even to its coordination geometry, but mainly to the molecular symmetry. [Display omitted] •No Metal-Boron bond paths have been found in any of the two complexes.•All Metal-Hydrogen bonds are intermediate between agostic and σ-terminal types.•Two 3c-2e bonding interactions are present within each MH2B moiety.•Other Metal-Ligand interactions follow the Dewar-Chatt-Duncanson model.•The presence of a plane of symmetry is essential for obtaining equivalent M-H-B bonds.