title: Conversion of azomethine moiety to carboxamido group at cobalt(III) center in model complexes of Co-containing nitrile hydratase.
abstract: The Co(III) complex of the Schiff base ligand N-2-mercaptophenyl-2'-pyridylmethyl-enimine (PyASH), namely, [Co(PyAS)(2)]Cl (1), has been synthesized via an improved method and its structure has been determined by X-ray crystallography. The two deprotonated ligands are arranged in mer configuration around the Co(III) center and the overall coordination geometry is octahedral. The coordinated azomethine function in 1 is rapidly converted into carboxamido group upon reaction with OH(-). The product is the bis carboxamido complex (Et(4)N)[Co(PyPepS)(2)] (2), reported by us previously. Reaction of H(2)O(2) with 1 in DMF affords [Co(PyASO(2))(PyPepSO(2))] (3), a species with mixed imine and carboxamido-N donor centers as well as S-bound sulfinates. Further reaction with H(2)O(2) in the presence of NaClO(4) converts 3 into the previously reported bis carboxamido/sulfinato complex Na[Co(PyPepSO(2))(2)] (4). The reaction conditions for the various transformation reactions for complexes 1-4 and the structure of 3 are also reported. The mechanism of the -CH=NR + [O] --> -C(=O)NHR transformation has been discussed. The reactions reported here provide convenient alternate routes for the syntheses of Co(III) complexes with coordinated carboxamide, thiolate, and/or sulfinate donors as models for the Co-site in the Co-containing nitrile hydratase(s).
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Tyler
authors.forename: M M
authors.initials: MM
authors.lastname: Olmstead
authors.forename: P K
authors.initials: PK
authors.lastname: Mascharak
mesh_terms: D001665:Binding Sites; D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006836:Hydro-Lyases / Q000737:chemistry* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D018716:Molecular Mimicry; D015394:Molecular Structure; D009282:Naphthalenesulfonates / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction; D013882:Thiosemicarbazones / Q000737:chemistry*
chemical_list: D009282:Naphthalenesulfonates; D009942:Organometallic Compounds; D013882:Thiosemicarbazones; C097966:azomethine H; D003035:Cobalt; D006836:Hydro-Lyases; C048831:nitrile hydratase