Structural and Dynamic Studies of Zinc, Gallium, and Cadmium Complexes of a Dicarboxylate Pendant-Armed Cross-Bridged Cyclen

✍ Scribed by Weijun Niu; Edward H. Wong; Gary R. Weisman; Yijie Peng; Carolyn J. Anderson; Lev N. Zakharov; James A. Golen; Arnold L. Rheingold

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 143 KB
• Volume: 2004
• Category: Article
• ISSN: 1434-1948
• DOI: 10.1002/ejic.200400075

✦ Synopsis

Abstract

Zn^II^, Ga^III^, and Cd^II^ complexes of a dicarboxylate pendant‐armed derivative of an important new cross‐bridged cyclen ligand were prepared and characterized spectrally. Crystal structures of the Zn^II^ and Ga^III^ complexes both feature pseudo‐octahedral metal centers, fully enveloped by the ligand’s cis‐N~4~O~2~ donor set with the zinc coordination sphere less distorted. All Ga−N and Ga−O bonds are significantly shorter than the corresponding values in the zinc structure. Solution NMR spectral studies revealed dynamic enantiomerization for the Zn^II^ complex with Δ__G__^≠^ = 12.3(1) kcal/mol (24 °C). By contrast, the Ga^III^ complex gave only slow‐exchange limit spectra up to the highest temperature measured [87(2) °C; Δ__G__^≠^ > 21.1(2) kcal/mol]. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)