五齿环戊二烯(四齿环丁二烯)镍(Ⅰ)衍生络合阳离子[Ni(C5R5)(C4R′4)]+的电化学还原反应

用循环伏安法, 计时电位法和计时电流法, 在二氯甲烷、乙腈、四氢呋哺和丙瞵撑碳酸酯等不同溶剂中, 在铂电极上研究了五齿环戊二稀(四齿环丁二稀)镍(Ⅰ)夹心络合阳离子, Ni(h~5-C_5R_5)(h~4-C_4R'_4)~+, (R=H,CH_3,R'=CH_3,C_6H_5)的电化学行为。实验结果表明: 对于R=H, R'=C_6H_5; R=CH_3, R'=C_6H_5的镍络离子为单电子的可逆还原反应, 产物为“19价电子壳层”的镍中性络合物。但是, 对于R=H, R'=CH_3; R=CH_3, R'=CH_3的镍络离子则因伴随有化学后置反应-二聚化反应而为不可逆的电极反应, 电化学还原反应的可逆性在四氢呋喃中有减小的趋势。此外, 用电解的方法对还原反应产物作了进一步的研究, 并对二聚分子的结构式提出建议。

ELECTROCHEMICAL REDUCTION OF h5-CYCLOPENTADIENYL-h4-CYCLOBUTADIENE-NICKEL-CATIONS,Ni(h5-C5R5)(h4-C4R4′)+

Electrochemical reduction of nickel sandwich complex-cations Ni(h~5-C_5eR_5) (h~4-C_4R'_4)~+, where R=H, CH_3; R'=CH_3, C_6H_5 was investigated at a Pt-electrode by means of cyclic voltametry, chronopotentiometry and chronoamperometry in dichloromethane, acetonitrile, tetrahydrofuran and propylenecarbonate (PC). The reduction are reversible and single electron processes for the compounds with R=H, R'=C_6H_5; R=CH_3, R'=C_6H_5 and the products are characteristic of “19-electron” nickel complexes. The complex cations exhibit an irreversible processes with coupled chemical reaction when R=H, R′=CH_3; R=CH_3, R′=CH_3. The stability of the reduction products was investigated further by bulk electrolysis. The reversibility of the electrochemical reduction tend to be reduced in THF.