5. Kartik Chandra Mondal, Sudipta Roy, Susmita De, Pattiyil Parameswaran, Birger Dittrich, Serhiy Demeshko, Fabian Ehret, Wolfgang Kaim, Herbert W. Roesky. Stabilization of a Two Coordinate Mono-Atomic Cobalt(0).
(Me2-cAAC:)2Co(0) (2) (Me2-cAAC: = cyclic (alkyl) amino carbene; :C(CH2)(CMe2)2N-2,6-iPr2C6H3)) was synthesized via the reduction of the precursor (Me2-cAAC:)2Co(I)Cl (1) with KC8 in THF. The cyclic voltammogram of 1 exhibits one electron reduction which rationalizes synthesis of a bent 2-metallaallene (2) from 1. Compound 2 contains one cobalt atom in the formal oxidation state zero which is stabilized by two Me2-cAAC: ligands. The Co-C bond distances are 1.871(2) and 1.877(2) Å with C-Co-C angle of 170.12(8)°. The EPR spectrum of 2 exhibits a broad resonance attributed to the unique quasi-linear structure which favors near degeneracy and gives rise to very rapid relaxation conditions. The cAAC–Co bond in 2 can be considered as a typical Dewar-Chatt-Duncanson type of bonding which in turn retains 2.5 electron pairs on the Co-atom as non-bonding electrons..