Tritopic (Cascade) and Ditopic Complexes of Halides with an Azacryptand

详细信息    查看全文

• 作者：Md. Alamgir Hossain ; Paula Morehouse ; Douglas Powell ; and Kristin Bowman-James
• 刊名：Inorganic Chemistry
• 出版年：2005
• 出版时间：April 4, 2005
• 年：2005
• 卷：44
• 期：7
• 页码：2143 - 2149
• 全文大小：174K
• 年卷期：v.44,no.7(April 4, 2005)
• ISSN：1520-510X

文摘

Structural aspects of the binding of halides in the octaaza cryptand (1,4,11,14,17,24,29,36-octa-azapentacyclo[12.12.12.2^6,9.2^19,22.2^31,34]-tetratetraconta-6(43),7,9(44),19(41),20,22(42),31(39),32,34(40)-nonaene, N(CH₂CH₂NHCH₂-p-xylyl-CH₂NHCH₂CH₂)₃N), L¹, were examined for fluoride, chloride, and bromide. Crystallographic results for twodifferent fluoride complexes indicated cascade-like coordination, with two fluoride ions inside the tren-based cavity,bridged by a water molecule. In the two different chloride structures, a single chloride and a water molecule occupiedthe cavity. The bromide structure contained two crystallographically independent cationic cryptands. Unit A consistedof a bromide on one side of the cavity and three disordered water molecules situated between the cryptand armson the other side. Unit B also had a bromide inside the cavity at one side, but a single molecule of water wascentered at the other side of the cavity. Association constants for the three ions, determined by NMR titrations inaqueous solution at pH 5, revealed log K_a = 3.15(5), 3.37(3), and 3.34(4) for fluoride, chloride, and bromide,respectively.