title: Easy access to bio-inspired osmium(II) complexes through electrophilic intramolecular C(sp2)-H bond cyclometalation.
abstract: Mild electrophilic C(sp2)-H cyclometalation of 2-phenylpyridine and N,N-dimethylbenzylamine by the chloro-bridged osmium(II) dimer [OsCl(micro-Cl)(eta6-C6H6)]2 in acetonitrile affords cyclometalated pseudotetrahedral OsII complexes [Os(C approximately N)(eta6-C6H6)(NCMe)]PF6 (C approximately N=o-C6H4py-kappa C,N (2) and o-C6H4CH2NMe2-kappa C,N (5), respectively) in good to excellent yields. The cyclometalation reactions are super sensitive to the nature of an external base. Sodium hydroxide is essential for cyclometalation of 2-phenylpyridine, but NaOH retards metalation of N,N-dimethylbenzylamine, the tertiary amine being self-sufficient as a base. Further reactions of compounds 2 and 5 with 1,10-phenanthroline or 2,2'-bipyridine (N approximately N) lead to the substitution of the eta6-bound benzene to produce octahedral species [Os(C approximately N)(N approximately N)(NCMe)2]PF6 or [Os(C approximately N)(N approximately N)2]PF6 in MeCN or MeOH as solvent, respectively. The cis configuration of the MeCN ligands in [Os(C approximately N)(phen)(NCMe)2]PF6 has been confirmed by an X-ray crystallographic study. Electrochemical investigation of the octahedral osma(II)cycles by cyclic voltammetry showed a pseudoreversible MIII/II redox feature at (-50)-(+109) and 190-300 mV versus Ag/AgCl in water and MeCN, respectively. As a possible application of the compounds, a rapid electron exchange between the reduced active site of glucose oxidase enzyme from Aspergillus niger and the electrochemically generated OsIII species has been demonstrated. The corresponding second-order rate constants cover the range (0.7-4.8)x10(6) M(-1) s(-1) at 25 degrees C and pH 7.
authors.affiliation: Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Coyoacán, 04511 México DF, Mexico.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Cerón-Camacho
authors.forename: David
authors.initials: D
authors.lastname: Morales-Morales
authors.forename: Simon
authors.initials: S
authors.lastname: Hernandez
authors.forename: Ronan
authors.initials: R
authors.lastname: Le Lagadec
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Ryabov
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry; D001234:Aspergillus niger / Q000201:enzymology; D001596:Benzylamines / Q000737:chemistry; D001665:Binding Sites; D002244:Carbon / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D004579:Electron Transport; D004583:Electrons; D005949:Glucose Oxidase / Q000737:chemistry / Q000378:metabolism; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D009942:Organometallic Compounds / Q000737:chemistry*; D009992:Osmium / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry
chemical_list: D000814:Aniline Compounds; D001596:Benzylamines; D009942:Organometallic Compounds; D011725:Pyridines; C035815:4-dimethylaminobenzylamine; D009992:Osmium; C058324:2-phenylpyridine; D002244:Carbon; D006859:Hydrogen; D005949:Glucose Oxidase