(+)589-[CoSCH(CH3)COO}(tren)]+, (−)589-[CoCH3SCH(CH3)COO}(tren)]2+, and (+)589-[CoS(O)2CH(CH3)COO}(tren)]+ (tren=tris(2-aminoethyl)amine) were prepared and assigned to the trans(tertiary amine nitrogen, S) isomer with the R carbon atom on the basis of the absorption, CD, and 1H NMR spectra. Racemization of the complexes was studied in aqueous solutions with ionic strength of 0.1, 0.2, or 1.0 (NaClO4) in the pH and temperature ranges of 5.96–6.86 and 19.9–49.5 °C, respectively. The CH3SCH(CH3)COO− and −O2SCH(CH3)COO− complexes follow the rate law, R=kr[OH−][complex]. The second-order rate constants (kr) for the former and the latter complexes are 4.6×103 (35.3 °C) and 7.8×103 (35.2 °C) mol−1 dm3s−1, respectively. The −SCH(CH3)COO− complex did not racemize under these conditions. Deuteration of the methine protons in the complexes was found to proceed simultaneously with the racemization. The differences in reactivity to racemization and proton exchange among three complexes were accounted for by the difference in electron-withdrawing effect of the −S–, S(CH3)–, and −S(O)2– groups, and by the difference in net charge of the complex ions.
合成并指认了(+)589-[CoSCH(
CH3)COO}(tren)]+、(−)589-[Co SCH( )COO}(tren)]2+和(+)589-[CoS(O)2CH( )COO}(tren)]+ (tren=tris(2-aminoethyl)胺)为trans(叔胺氮、
硫)异构体和R碳原子, 依据的是吸收、CD和1H核磁谱。在
水溶液中研究了这些配合物的消旋过程, 离子强度为0.1、0.2或1.0 (NaClO4), pH值和温度范围分别为5.96–6.86和19.9–49.5 °C。 SCH( )COO−和−O2SCH( )COO−配合物遵循速率定律, R=kr[OH−][配合物]。上述和下述配合物的二级速率常数(kr)分别为4.6×103 (35.3 °C)和7.8×103 (35.2 °C) mol−1 dm3s−1。在这些条件下, −SCH( )COO−配合物没有发生消旋。配合物中的次甲基质子
氘代过程是与消旋同时发生的。三种配合物在消旋和质子交换反应性上的差异可归结为−S–、S( )–和−S(O)2– 的吸电子效应不同以及配合物离子的净电荷不同。