Pyridyl-Based Pentadentate Ligands: Base-Catalyzed Hydrolysis of asym-[Co(dmptacn)Cl]2+
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- 作者：W. Gregory Jackson ; Alistair J. Dickie ; Rajumati Bhula ; Josephine A. McKeon ; Leone Spiccia ; Suzanne J. Brudenell ; David C. R. Hockless ; and Anthony C. Willis
- 刊名：Inorganic Chemistry
- 出版年：2004
- 出版时间：October 18, 2004
- 年：2004
- 卷：43
- 期：21
- 页码：6549 - 6556
- 全文大小：151K
- 年卷期：v.43,no.21(October 18, 2004)
- ISSN：1520-510X
文摘
The [Co(dmptacn)Cl]2+ (dmptacn = 1,4-bis(pyridylmethyl)-1,4,7-triazacyclononane) complex has been shown to bethe asym isomer through 1D and 2D NMR studies, its optical resolution, and the single-crystal X-ray structure ofits perchlorate salt. The kinetics of base-catalyzed hydrolysis establishes the usual [OH-] dependence (kOH =0.040 M-1 s-1, 25 
C, I = 1.0 M, NaCl), but D-exchange experiments reveal that substantial if not completereaction proceeds via the new pseudoaminate mechanism, i.e., via deprotonation at an 
rs/alpha.gif" BORDER=0>-CH2 center rather thanthe NH. The significant kinetic isotope effect (kH/kD = 2.1) is interpreted in terms of rate-limiting deprotonationfollowed by reprotonation of the conjugate base at a rate competitive with loss of Cl-. NMR and polarimetricstudies establish geometric and optical retention for the hydrolysis reaction and exclude even the transient formationof a sym isomer intermediate.
C, I = 1.0 M, NaCl), but D-exchange experiments reveal that substantial if not completereaction proceeds via the new pseudoaminate mechanism, i.e., via deprotonation at an rs/alpha.gif" BORDER=0>-CH2 center rather thanthe NH. The significant kinetic isotope effect (kH/kD = 2.1) is interpreted in terms of rate-limiting deprotonationfollowed by reprotonation of the conjugate base at a rate competitive with loss of Cl-. NMR and polarimetricstudies establish geometric and optical retention for the hydrolysis reaction and exclude even the transient formationof a sym isomer intermediate.