Molecular Structure of Nitro- and Nitrito-Copper Complexes as Reaction Intermediates in Electrochemical Reduction of Nitrite to Dinitrogen Oxide
作者:Nobutoshi Komeda、Hirotaka Nagao、Yoshinori Kushi、Gin-ya Adachi、Masatatsu Suzuki、Akira Uehara、Koji Tanaka
DOI:10.1246/bcsj.68.581
日期:1995.2
Copper-nitrito and -nitro isomers, [Cu(ONO)(tpa)]PF6 and [Cu(NO2)(tpa)]PF6 (tpa = tris[(2-pyridyl)methyl]amine) were isolated and the molecular structures were determined by X-ray analysis. [Cu(ONO)(tpa)]PF6 (C18H18N5O2PF6Cu) crystallizes in the monoclinic space group P21/a with a = 13.374(2), b = 14.033(2), c = 13.455(2) Å, β = 119.10(1)°, V = 2206.5(6) Å3, and Z = 4. [Cu(NO2)(tpa)]PF6 (C18H18N5O2PF6Cu) crystallizes in the orthorhombic space group I/ba2 with a = 16.718(3), b = 17.554(3), c = 14.785(3) Å, V = 4338(1) Å3, and Z = 8. Those nitrito- and nitro-complexes exist as an equilibrium mixture in solutions. Electrochemical reduction of NO2− in the presence of [Cu(H2O)(tpa)](ClO4)2 at −0.4 V in H2O (pH 7.0) catalytically produced N2O with concomitant evolution of a small amount of NO via the nitro and nitrito adducts.
铜氮王与硝基异构体 [Cu(ONO)(tpa)]PF6 和 [Cu(NO2)(tpa)]PF6(tpa = 三[(2-吡啶基)甲基]胺)被分离,并通过 X 射线分析确定了其分子结构。[Cu(ONO)(tpa)]PF6 (C18H18N5O2PF6Cu) 结晶于单斜晶系 P21/a 空间组,参数为 a = 13.374(2) Å, b = 14.033(2) Å, c = 13.455(2) Å, β = 119.10(1)°, V = 2206.5(6) Å3,Z = 4。[Cu(NO2)(tpa)]PF6 (C18H18N5O2PF6Cu) 则结晶在正交晶系 I/ba2 空间组,参数为 a = 16.718(3) Å, b = 17.554(3) Å, c = 14.785(3) Å, V = 4338(1) Å3,Z = 8。这些氮酸盐和硝酸盐复合物在溶液中以平衡混合物存在。在 H2O (pH 7.0) 中存在 [Cu(H2O)(tpa)](ClO4)2 的情况下,NO2− 在 -0.4 V 处的电化学还原催化产生 N2O,同时通过硝酸和氮酸加成物伴随生成少量 NO。