Coia G M, Demadis K D, Meyer T J
Department of Chemistry, Venable and Kenan Laboratories, CB 3290, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA.
Inorg Chem. 2000 May 15;39(10):2212-23. doi: 10.1021/ic0000505.
The oxidations of cis- and trans-OsIII(tpy)(Cl)2(NH3), cis-OsII(bpy)2(Cl)(NH3), and OsII(typ)(bpy)(NH3)2 have been studied by cyclic voltammetry and by controlled-potential electrolysis. In acetonitrile or in acidic, aqueous solution, oxidation is metal-based and reversible, but as the pH is increased, oxidation and proton loss from coordinated ammonia occurs. cis- and trans-OsIII(tpy)(Cl)2(NH3) are oxidized by four electrons to give the corresponding OsVI nitrido complexes, [OSVI(typ)(Cl)2(N)]+. Oxidation of Os(typ)(bpy)(NH3)2 occurs by six electrons to give Os(tpy)(bpy)(NO)3. Oxidation of cis-OsII(bpy)2(Cl)(NH3) at pH 9.0 gives cis-OsII(bpy)2(Cl)(NO)2 and the mixed-valence form of the mu-N2 dimer [cis-[Os(bpy)2(Cl)2mu-N2)3. With NH4+ added to the electrolyte, cis-OsII(bpy)2(Cl)(N2) is a coproduct. The results of pH-dependent cyclic voltammetry measurements suggest OsIV as a common intermediate in the oxidation of coordinated ammonia. For cis- and trans-[OsIII(tpy)(Cl)2(NH3)]+, OsIV is a discernible intermediate. It undergoes further pH-dependent oxidation to [OsVI(tpy)(Cl)2(N)]+. For [OsII(tpy)(bpy)(NH3)]2+, oxidation to OsIV is followed by hydration at the nitrogen atom and further oxidation to nitrosyl. For cis-[OsII(bpy)2(Cl)-(NH3)]+, oxidation to OsIV is followed by N-N coupling and further oxidation to [cis-[Os(bpy)2(Cl)2(mu-N2)]3+. At pH 9, N-N coupling is competitive with capture of OsIV by OH- and further oxidation, yielding cis-[OsII(bpy)2(Cl)(NO)]2+.
通过循环伏安法和控制电位电解法研究了顺式和反式-OsIII(tpy)(Cl)2(NH3)、顺式-OsII(bpy)2(Cl)(NH3)以及OsII(typ)(bpy)(NH3)2的氧化过程。在乙腈或酸性水溶液中，氧化是基于金属的且可逆，但随着pH值升高，配位氨会发生氧化和质子损失。顺式和反式-OsIII(tpy)(Cl)2(NH3)被四电子氧化生成相应的OsVI氮化物配合物[OSVI(typ)(Cl)2(N)]+。Os(typ)(bpy)(NH3)2被六电子氧化生成Os(tpy)(bpy)(NO)3。顺式-OsII(bpy)2(Cl)(NH3)在pH 9.0时氧化生成顺式-OsII(bpy)2(Cl)(NO)2以及μ-N2二聚体的混合价态形式[顺式-[Os(bpy)2(Cl)2μ-N2)3。向电解质中添加NH4+时，顺式-OsII(bpy)2(Cl)(N2)是副产物。pH依赖的循环伏安法测量结果表明OsIV是配位氨氧化过程中的常见中间体。对于顺式和反式-[OsIII(tpy)(Cl)2(NH3)]+，OsIV是可辨别的中间体。它会进一步发生pH依赖的氧化生成[OsVI(tpy)(Cl)2(N)]+。对于[OsII(tpy)(bpy)(NH3)]2+，氧化生成OsIV后，氮原子处会发生水合作用并进一步氧化生成亚硝酰基。对于顺式-[OsII(bpy)2(Cl)-(NH3)]+，氧化生成OsIV后会发生N-N偶联并进一步氧化生成[顺式-[Os(bpy)2(Cl)2(μ-N2)]3+。在pH 9时，N-N偶联与OH-捕获OsIV并进一步氧化存在竞争，生成顺式-[OsII(bpy)2(Cl)(NO)]2+。
