Synthesis, Structure, and Bonding of Novel Homodinuclear Cobalt and Nickel Borylene Complexes

Abstract

Herein we report for the first time full details on the synthesis and structural characterization of novel homodinuclear bridging cobalt and nickel borylene complexes containing bridging carbonyl ligands, an unusual coordination motif rarely before observed for homodinuclear borylene complexes. Furthermore, the homodinuclear nickel complex represents the first instance of a nickel borylene complex. Quantum chemical analyses of charge-density topology, electron localization function (ELF) and natural charges indicate the absence of direct metal-metal bonds in both the cobalt and nickel systems, in contradiction with electron counting. The topology of the Laplacian of the electron density and of the ELF around the bridging boron atom is consistent with a bis-metallo-substituted borane situation for the dicobalt system, but with a three-center-bonding borylene for the dinickel complex.

Boranediyl‐ and Diborane(4)‐1,2‐diyl‐Bridged Platinum A‐Frame Complexes

“…Calculations based on the quantum theory of atoms in molecules (QTAIM) and on the electron‐localization function (ELF) revealed that the calculated bonding situation—that is, borylene versus boranediyl—strongly depends on the choice of exchange‐correlation functional . Similar calculations on homodinuclear nickel ( II ) and cobalt ( III ) μ ‐borylene complexes suggested that the dinickel complex should be described as a true bridging borylene whereas bonding in the dicobalt complex is closer to the boranediyl model, irrespective of the choice of density functional . Additionally, complexes I – III are all stabilized by delocalization of the metal–metal bonding molecular orbital over the empty orbitals of the boron bridge and thus fulfil the 18 valence electron rule.…”

“…[5] Similarc alculations on homodinuclear nickel (II)a nd cobalt (III) m-borylenec omplexes suggested that the dinickel complex shouldb ed escribed as at rue bridging borylene whereasb onding in the dicobalt complex is closer to the boranediylm odel,i rrespective of the choice of density functional. [7] Additionally,c omplexes I-III are all stabilized by delocalization of the metal-metal bonding molecular orbital over the empty orbitals of the boron bridgea nd thusf ulfil the 18 valencee lectron rule.…”

Silylene–Nickel Promoted Cleavage of B−O Bonds: From Catechol Borane to the Hydroborylene Ligand

“…The molecular structure of 3 (Figure ) reveals that it is a terminal hydroborylene nickel complex, with a HB: moiety coordinated by two NHC ligands which have migrated from nickel. As such, 3 is the first example of any metal complex containing a terminal :BH ligand . Notably, the Ni II center of 3 adopts a highly distorted trigonal‐planar geometry (∡(Cl‐Ni‐Si)=149.80(7)°, ∡(B‐Ni‐Si)=78.21(7) o ), due to attractive interactions between the silyl and borylene moieties (d(Si⋅⋅⋅B)=2.624(2) Å; sum of van der Waal's radii=3.90 Å).…”

Analysis of Tertiary Phosphanes, Arsanes, and Stibanes as Bridging Ligands in Dinuclear Group 9 Complexes

“…For carbene (or analogous borylene) bridges, the number of attractors is known to depend sensitively on details of the actual bonding situation 53. 57…”