872993-25-4Relevant articles and documents
Hexanickel enediolate cluster generated in an acireductone dioxygenase model reaction
Rudzka, Katarzyna,Grubel, Katarzyna,Arif, Atta M.,Berreau, Lisa M.
, p. 7623 - 7625 (2010)
A nickel(II) enediolate cluster (2) forms upon treatment of [(6-Ph 2TPA)Ni(PhC(O)C(OH)C(O)Ph)]ClO4 (1) with Me4NOH 5H2O in CH3CN. Crystallographic studies of 2 revealed a hexanuclear structure of S6 symmetry with a formula of {[Ni(PhC(O)C(O)C(O)Ph)(CH3OH)] 1.33CH3OH}6. Because isolation of bulk amounts of 2 from the reaction involving 1 proved impossible, a solvation analogue of 2 (labeled 5) was generated from admixture of Ni(ClO4)2 6H2O, 2-hydroxy-1,3- diphenylpropane-1,3-dione, and Me4NOH 5H2O in CH 3OH/CH3CN. Complex 5 is formulated as {[Ni(PhC(O)C(O)C(O) Ph)(H2O)] H2O 0.25CH3CN}6 based on elemental analysis, a molecular weight determination, UV-vis, and a magnetic moment measurement. Treatment of 5 with O2 and 6-Ph2TPA (6 equiv) results in the formation of CO and [(6-Ph2TPA)Ni(O 2CPh)2(H2O)] (3), the latter of which was isolated in 69% yield. The level of 18O incorporation in this reaction matches that for a reaction wherein 2 is generated from 1. These results provide evidence that a nickel(II) enediolate cluster is the O 2 reactive species in a previously reported model reaction for nickel(II)-containing acireductone dioxygenase.
Carboxylate coordination chemistry of a mononuclear Ni(II) center in a hydrophobic or hydrogen bond donor secondary environment: Relevance to acireductone dioxygenase
Szajna-Fuller, Ewa,Chambers, Bonnie M.,Arif, Atta M.,Berreau, Lisa M.
, p. 5486 - 5498 (2008/10/09)
A series of Ni(II) carboxylate complexes, supported by a chelate ligand having either secondary hydrophobic phenyl groups (6-Ph2TPA, N,N-bis((6-phenyl-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine) or hydrogen bond donors (bnpapa, N,N-bis((6-neopentylamino-2-pyridyl)methyl)-N-((2-pyridyl) methyl)amine), have been prepared and characterized. X-ray crystallographic studies of [(6-Ph2TPA)Ni(O2C(CH2) 2SCH3)]ClO4·CH2Cl 2 (4-CH2Cl2) and [(6-Ph2TPA) Ni(O2-CCH2SCH3)]ClO4·1. 5CH2Cl2 (5·1.5CH2Cl2) revealed that each complex contains a distorted octahedral Ni(II) center and a bidentate carboxylate ligand. A previously described benzoate complex ([(6-Ph2TPA)Ni(O2CPh)]ClO4 (3)) has similar structural characteristics. Recrystallization of dry powdered samples of 3, 4·0.5CH2Cl2, and 5 from wet organic solvents yielded a second series of crystalline Ni(II) carboxylate complexes having a coordinated monodentate carboxylate ligand ([(6-Ph2TPA)Ni(H 2O)(O2CPh)]ClO4 (6), [(6-Ph2TPA) Ni(H2O)(O2C(CH2)2SCH 3)]ClO4·0.2CH2Cl2 (7·0.2CH2Cl2), [(6-Ph2TPA)Ni(H 2O)(O2CCH2SCH3)]ClO4 (8)) which is stabilized by a hydrogen-bonding interaction with a Ni(II)-bound water molecule. In the cationic portions of 7·0.2CH2Cl2 and 8, weak CH/π interactions are also present between the methylene units of the carboxylate ligands and the phenyl appendages of the 6-Ph2TPA ligands. A formate complex of the formulation [(6-Ph2TPA)Ni(H 2O)(O2CH)]ClO4 (9) was isolated and characterized. The mononuclear Ni(II) carboxylate complexes [(bnpapa)Ni(O 2CPh)]ClO4 (10), [(bnpapa)Ni(O2C(CH 2)2SCH3)]ClO4 (11), [(bnpapa)Ni(O2CCH2SCH3)]ClO4 (12), and [(bnpapa)Ni(O2CH)]ClO4 (13) were isolated and characterized. Two crystalline solvate forms of 10 (10·CH3CN and 10·CH2Cl2) were examined by X-ray crystallography. In both, the distorted octahedral Ni(II) center is ligated by a bidentate benzoate ligand, one Ni(II)-bound oxygen atom of which accepts two hydrogen bonds from the supporting bnpapa chelate ligand. Spectroscopic studies of 10-13 suggest that all contain a bidentate carboxylate ligand, even after exposure to water. The combined results of this work enable the formulation of a proposed pathway for carboxylate product release from the active site Ni(II) center in acireductone dioxygenase.
