Co(III) Complexes with N2(SO)2-Type Equatorial Planar Ligands Similar to the Active Center of Nitrile Hydratase: Role of the Sulfenate Group in the Enzymatic Reaction

In order to gain an understanding of the role of the sulfenyl group of nitrile hydratase (NHase), a new Co(III) complex with a sulfenyl-type ligand (LCO:N2(SO)2), Na[CoIII(LC=O:N2(SO)2)(tBuNC)2] (2), was synthesized. The compound includes two amide groups, two sulfenate sulfurs in the equatorial plane, and two tBuNC molecules in the axial positions. Characterization of the compound was performed by UV−vis spectroscopic, IR spectral, thermogravimetric (TG), and X-ray structure analytical methods. The results are discussed in the context of Co(III) complexes containing the corresponding sulfur-type (LCO:N2S2) (1) and sulfinyl-type ligands (LCO:N2(SO2)2) (3). Complex 2 crystallized with the formula Na[CoIII(LC=O:N2(SO)2)(tBuNC)2]·urea·2H2O·0.5EtOH. The X-ray structure revealed that the Co(III) complex has an octahedral geometry with Co−S = av. 2.221 A, Co−N = av. 1.998 A, and Co−C = av. 1.87 A. The sulfenyl oxygen and amidate carbonyl oxygen are linked to urea, water, EtOH, and Na+ and participate in a hydro...