Lutterman Daniel A, Degtyareva Natalya N, Johnston Dean H, Gallucci Judith C, Eglin Judith L, Turro Claudia
Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA.
Inorg Chem. 2005 Jul 25;44(15):5388-96. doi: 10.1021/ic048377j.
Various substituted dirhodium tetraformamidinate complexes, Rh(2)(R-form)(4) (R = p-CF(3), p-Cl, p-OCH(3), m-OCH(3); form = N,N'-diphenylformamidinate), and the new complex Rh(2)(tpgu)(4) (tpgu = 1,2,3-triphenylguanidinate) have been investigated as potential agents for the photoremediation of saturated halogenated aliphatic compounds, RX (R = alkyl group). The synthesis and characterization of the complexes is reported, and the crystal structure of Rh(2)(tpgu)(4) is presented. The lowest energy transition of the complexes is observed at approximately 870 nm and the complexes react with alkyl chlorides and alkyl bromides under low energy irradiation (lambda(irr) > or = 795 nm), but not when kept in the dark. The metal-containing product of the photochemical reaction with RX (X = Cl, Br) is the corresponding mixed-valent Rh(2)(II,III)X (X = Cl, Br) complex, and the crystal structure of Rh(2)(p-OCH(3)-form)(4)Cl generated photochemically from the reaction of the corresponding Rh(2)(II,II) complex in CHCl(3) is presented. In addition, the product resulting from the dimerization of the alkyl fragment, R(2), is also formed during the reaction of each dirhodium complex with RX. A comparison of the dependence of the relative reaction rates on the reduction potentials of the alkyl halides and their C-X bond dissociation energies are consistent with an outer-sphere mechanism. In addition, the relative reaction rates of the metal complexes with CCl(4) decrease with the oxidation potential of the dirhodium compounds. The mechanism of the observed reactivity is discussed and compared to related systems.
已对多种取代的四甲脒基二铑配合物Rh₂(R - form)₄（R = p - CF₃、p - Cl、p - OCH₃、m - OCH₃；form = N,N'-二苯基甲脒基）以及新配合物Rh₂(tpgu)₄（tpgu = 1,2,3 - 三苯基胍基）作为饱和卤代脂肪族化合物RX（R = 烷基）光修复潜在试剂进行了研究。报道了这些配合物的合成与表征，并给出了Rh₂(tpgu)₄的晶体结构。配合物的最低能量跃迁在约870 nm处观测到，并且这些配合物在低能量辐射（λirr≥795 nm）下与烷基氯和烷基溴发生反应，但在黑暗中保存时则不反应。与RX（X = Cl、Br）光化学反应的含金属产物是相应的混合价Rh₂(II,III)X（X = Cl、Br）配合物，给出了由相应的Rh₂(II,II)配合物在CHCl₃中光化学反应生成的Rh₂(p - OCH₃ - form)₄Cl的晶体结构。此外，在每个二铑配合物与RX反应过程中还形成了烷基片段R₂二聚产生的产物。相对反应速率对烷基卤化物还原电位及其C - X键解离能依赖性的比较与外层球机制一致。此外，金属配合物与CCl₄的相对反应速率随二铑化合物的氧化电位降低。讨论了观察到的反应性机制并与相关体系进行了比较。
