Department of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, Republic of South Africa.
Inorg Chem. 2010 Feb 1;49(3):952-9. doi: 10.1021/ic901676e.
The synthesis of the first rhodium(I) cyclooctadiene complexes containing tetrathiafulvalene (TTF) groups substituted on a beta-diketonato ligand in either the methine position (3 position), [Rh(cod)(H(3)CCOC{S-TTF-(MeS)(3)}COCH(3))] (3), or terminal position (1 position), [Rh(cod){(Me(3)-TTF)COCHCOCH(3)}] (4), is reported. The effect of the beta-diketonato substitution position on the kinetics of substitution of the TTF-containing beta-diketonato ligand with 1,10-phenanthroline from 3 and 4 to give Rh(cod)(phen), as well as on the electrochemical properties of 3 and 4, was investigated. Second-order substitution rate constants, k(2), in methanol were found to be almost independent of the substitution position, with 4 (k(2) = 2.09 x 10(3) dm(3) mol(-1) s(-1)) reacting only about twice as fast as 3. An appreciable solvent pathway in the substitution mechanism was only observed for 4 with k(s) = 42 s(-1). A complete mechanism for both substitution reactions is proposed. The electrochemistry of 3 and 4 in CH(2)Cl(2)/0.10 mol dm(-3) [N((n)Bu)(4)][B(C(6)F(5))(4)] showed three redox processes. Two of these were electrochemically reversible and are associated with the redox-active TTF group. For 3, TTF-based formal reduction potentials, E degrees', were observed at 0.082 and 0.659 V vs Fc/Fc(+), respectively; 4 exhibited them at -0.172 and 0.703 V vs Fc/Fc(+) at a scan rate of 100 mV s(-1). A Rh(II)/Rh(I) redox couple was observed at E degrees' = 0.89 V for 3, after both TTF oxidations were completed, and at 0.51 V for 4; this is between the two TTF redox processes. The more difficult oxidation of the Rh(I) center of 3 indicates more effective electron-withdrawing from the Rh(I) center to the first-oxidized TTF(+) group at the methine position of the beta-diketonato ligand of 3(+) than to the terminal-substituted TTF(+) group in 4(+).
首次报道了含有噻吩[2,3-b]噻吩（TTF）基团的铑（I）环辛二烯配合物的合成，β-二酮配体在亚甲基（3 位）或末端位置（1 位）取代，[Rh(cod)(H(3)CCOC{S-TTF-(MeS)(3)}COCH(3))]（3）和[Rh(cod){(Me(3)-TTF)COCHCOCH(3)}]（4）。研究了β-二酮配体取代位置对 3 和 4 与 1,10-菲咯啉取代 TTF 含β-二酮配体形成Rh(cod)(phen)的动力学以及 3 和 4 的电化学性质的影响。在甲醇中，发现二级取代速率常数 k(2)几乎与取代位置无关，4（k(2) = 2.09 x 10(3) dm(3) mol(-1) s(-1)）的反应速度仅比 3 快约两倍。只有 4 观察到明显的溶剂途径，k(s) = 42 s(-1)。对两种取代反应都提出了完整的机制。3 和 4 在 CH(2)Cl(2)/0.10 mol dm(-3)[N((n)Bu)(4)][B(C(6)F(5))(4)]中的电化学研究表明有三个氧化还原过程。其中两个是电化学可逆的，与氧化还原活性的 TTF 基团有关。对于 3，TTF 基形式还原电位 E degrees'分别在 0.082 和 0.659 V 相对于 Fc/Fc(+)；4 在 100 mV s(-1)的扫描速率下，它们在-0.172 和 0.703 V 相对于 Fc/Fc(+)。在 3 中，在完成两个 TTF 氧化后观察到 Rh(II)/Rh(I)氧化还原对，E degrees'= 0.89 V，在 4 中观察到 0.51 V；这介于两个 TTF 氧化还原过程之间。3 中 Rh(I)中心更难氧化表明，与 4(+)中末端取代的 TTF(+)基团相比，Rh(I)中心对β-二酮配体亚甲基位置上第一个氧化的 TTF(+)基团的电子吸引力更大。
