Stability Constants: A New Twist in Transition Metal Bispidine Chemistry

详细信息    查看全文

• 作者：Karin Born ; Peter Comba ; Rosana Ferrari ; Geoffrey A. Lawrance ; Hubert Wadepohl
• 刊名：Inorganic Chemistry
• 出版年：2007
• 出版时间：January 22, 2007
• 年：2007
• 卷：46
• 期：2
• 页码：458 - 464
• 全文大小：164K
• 年卷期：v.46,no.2(January 22, 2007)
• ISSN：1520-510X

文摘

Transition metal complexes with 2,4-substituted tetradentate, 2,3,4- and 2,4,7-substituted pentadentate, and 2,3,4,7-substituted hexadentate bispidine ligands (bispidine = 3,7-diazabicyclo[3.3.1]nonane) with two tertiary amine andtwo, three, or four pyridine donors are relatively stable (10 < log K_CuL < 18). Interestingly, the two isomeric pentadentateligands have very different stabilities with a variety of metal ions and, depending on the metal ion, one of theisomers leads to more stable complexes than the hexadentate and the other to less stable complexes than thetetradentate ligand. Another interesting observation is that the complex stabilities of all bispidine ligands reportedhere do not follow the Iriving-Williams series since the stability constants of the cobalt(II) complexes are up to 4log units larger than those of the corresponding nickel(II) complexes. All these observations are analyzed on thebasis of subtle distortions of the coordination geometries, and these have been related previously to Jahn-Teller-derived distortions for the copper(II) complexes. However, similar but less pronounced structural properties areobserved with other metal centers, as shown, e.g., with the experimental structures of the two zinc(II) complexeswith the isomeric pentadentate ligands reported here. The structural properties and the related stabilities are alsodiscussed on the basis of force field calculations.