Cerón-Camacho Ricardo, Morales-Morales David, Hernandez Simon, Le Lagadec Ronan, Ryabov Alexander D
Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Coyoacán, 04511 México DF, Mexico.
Inorg Chem. 2008 Jun 2;47(11):4988-95. doi: 10.1021/ic800251t. Epub 2008 May 6.
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.
在乙腈中，氯桥联的锇（II）二聚体[OsCl(μ-Cl)(η6-C6H6)]2对2-苯基吡啶和N,N-二甲基苄胺进行温和的亲电C(sp2)-H环金属化反应，以良好至优异的产率得到环金属化的拟四面体OsII配合物[Os(C≡N)(η6-C6H6)(NCMe)]PF6（C≡N分别为邻-C6H4py-κC,N (2)和邻-C6H4CH2NMe2-κC,N (5)）。环金属化反应对外部碱的性质极为敏感。氢氧化钠对于2-苯基吡啶的环金属化是必不可少的，但NaOH会阻碍N,N-二甲基苄胺的金属化，叔胺本身作为碱就足够了。化合物2和5与1,10-菲咯啉或2,2'-联吡啶（N≡N）进一步反应，导致η6-键合的苯被取代，分别在乙腈或甲醇作为溶剂的情况下生成八面体物种[Os(C≡N)(N≡N)(NCMe)2]PF6或[Os(C≡N)(N≡N)2]PF6。通过X射线晶体学研究证实了[Os(C≡N)(phen)(NCMe)2]PF6中MeCN配体的顺式构型。通过循环伏安法对八面体锇（II）环进行电化学研究表明，在水中和乙腈中，相对于Ag/AgCl，在(-50)-(+109)和190-300 mV处分别出现了一个准可逆的MIII/II氧化还原特征。作为这些化合物的一种可能应用，已证明黑曲霉葡萄糖氧化酶还原活性位点与电化学产生的OsIII物种之间存在快速电子交换。在25℃和pH 7下，相应的二级速率常数范围为(0.7-4.8)×10(6) M(-1) s(-1)。
