1/1 METAL-COMPLEXES OF BIVALENT COBALT, NICKEL, COPPER, ZINC, AND CADMIUM WITH THE TRIPODAL LIGAND TRIS[2-(DIMETHYLAMINO)ETHYL]AMINE - THEIR STABILITIES AND THE X-RAY CRYSTAL-STRUCTURE OF ITS COPPER(II) COMPLEX SULFATE

被引:61
作者
ANDEREGG, G [1 ]
GRAMLICH, V [1 ]
机构
[1] ETH ZENTRUM,INST CRYSTALLOG & PETROG,CH-8092 ZURICH,SWITZERLAND
关键词
D O I
10.1002/hlca.19940770312
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The complex formation by Co2+, Ni2+, Cu2+, Zn2+, and Cd2+ with tris[2-(dimethylamino)ethyl]amine (N(CH(2)CH(2)NMe(2))(3), Me(6)tren) was investigated at 25 degrees and at an ionic strength of 1, using VIS spectroscopy and potentiometric measurements. The stability constants of these complexes are compared with those of tris(2-aminoethyl)amine (N(CH2CH2NH2)(3), tren), obtained under the same conditions. The values of the constants for Me(6)tren are much lower than those for tren, due to the bulky Me substituents. The values of the constants can be correlated with the ability of the individual metal ions to adopt coordination number 5. This appears to be easier for Cu2+ and Co2+ than for Cd2+ and Zn2+ and is very difficult for Ni2+. The 1:1 complexes [ML(H2O)](2+) are monoprotonic acids whose pK(s), values are similar or lower than those of the corresponding aquametal ions. The X-ray crystal structure of the copper(II) complex [Cu(SO4)(Me(6)tren)].8H(2)O reveals pentacoordination at the central ion. The UV/VIS spectra of the aqueous solutions of the Co2+, Ni2+, and Cu2+ 1:1 complexes confirm that the same coordination number is present also in these complexes.
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页码:685 / 690
页数:6
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