title: Influence of water on the formation of O2-reactive divalent metal enolate complexes of relevance to acireductone dioxygenases.
abstract: Reaction conditions were evaluated for the preparation of [(6-PhTPA)Ni(PhC(O)C(OH)C(O)Ph)]ClO(4) (3) and [(6-Ph(2)TPA)Co(PhC(O)C(OH)C(O)Ph)]ClO(4) (7), two complexes of structural relevance to the enzyme/substrate (ES) adduct in Ni(II)- and Co(II)-containing forms of acireductone dioxygenase. The presence of water in reactions directed at the preparation of 3 and 7 was found to result in isomerization of the enolate precursor 2-hydroxy-1,3-diphenylpropane-1,3-dione to give the ester 2-oxo-2-phenylethylbenzoate. Performing synthetic procedures under dryer conditions reduced the amount of ester production and enabled the isolation of 3 in high yield. This complex was comprehensively characterized, including by X-ray crystallography. Using similar conditions for the 6-Ph(2)TPACo-containing system, the amount of ester generated was only modestly affected, but the formation of a benzoate complex ([(6-Ph(2)TPA)Co(O(2)CPh)]ClO(4), 10) resulting from ester hydrolysis was prevented. The best preparation of 7 was found to involve dry conditions and short reaction times. The approach outlined herein toward determining appropriate reaction conditions for the preparation of 3 and 7 involved the preparation and characterization of several air-stable (6-PhTPA)Ni- and (6-Ph(2)TPA)Co-containing analog complexes having enolate, solvent, and benzoate ligands. These complexes were used as paramagnetic (1)H NMR standards for evaluation of reaction mixtures containing 3 and 7.
authors.affiliation: Department of Chemistry & Biochemistry, Utah State University, Logan, UT, USA.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Grubel
authors.forename: Gajendrasingh K
authors.initials: GK
authors.lastname: Ingle
authors.forename: Amy L
authors.initials: AL
authors.lastname: Fuller
authors.forename: Atta M
authors.initials: AM
authors.lastname: Arif
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Berreau
mesh_terms: D003035:Cobalt / Q000737:chemistry; D056831:Coordination Complexes / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D049308:Dioxygenases / Q000378:metabolism*; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry* / Q000378:metabolism; D013379:Substrate Specificity; D014867:Water / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D011725:Pyridines; D014867:Water; D003035:Cobalt; D009532:Nickel; D049308:Dioxygenases; C083734:aci-reductone oxidase (CO-forming); D010100:Oxygen