Acireductone dioxygenase- (ARD-) type reactivity of a nickel(II) complex having monoanionic coordination of a model substrate: product identification and comparisons to unreactive analogues.
A mononuclear Ni(II) complex ([(6-Ph2TPA)Ni(PhC(O)C(OH)C(O)Ph)]ClO4 (1)), supported by the 6-Ph2TPA chelate ligand (6-Ph2TPA = N,N-bis((6-phenyl-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine) and containing a cis-beta-keto-enolate ligand having a C2 hydroxyl substituent, undergoes reaction with O2 to produce a Ni(II) monobenzoate complex ([(6-Ph2TPA)Ni(O2CPh)]ClO4 (3)), CO, benzil (PhC(O)C(O)Ph), benzoic acid, and other minor unidentified phenyl-containing products. Complex 3 has been identified through independent synthesis and was characterized by X-ray crystallography, 1H NMR, FAB-MS, FTIR, and elemental analysis. A series of cis-beta-keto-enolate Ni(II) complexes supported by the 6-Ph2TPA ligand ([(6-Ph2TPA)Ni(PhC(O)CHC(O)Ph)]ClO4 (4), [(6-Ph2TPA)Ni(CH3C(O)CHC(O)CH3)]ClO4 (5), and [(6-Ph2TPA)Ni(PhC(O)CHC(O)C(O)Ph) (6)) have been prepared and characterized. While these complexes exhibit structural and/or spectroscopic similarity to 1, all are unreactive with O2. The results of this study are discussed in terms of relevance to Ni(II)-containing acireductone dioxygenase enzymes, as well as in the context of recently reported cofactor-free, quercetin, and beta-diketone dioxygenases.
Szajna-Fuller
Ewa
E
Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, USA.
Rudzka
Katarzyna
K
Arif
Atta M
AM
Berreau
Lisa M
LM
D001665:Binding Sites; D018360:Crystallography, X-Ray; D049308:Dioxygenases / Q000378:metabolism*; D007477:Ions / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D008958:Models, Molecular; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D011522:Protons; D013379:Substrate Specificity
D007477:Ions; D011522:Protons; D009532:Nickel; D049308:Dioxygenases; C083734:aci-reductone oxidase (CO-forming); D010100:Oxygen