Hi, Thorsten! Could this *very short* article be of interest?

"Spectrophotometric determination of rhodium with EDTA and CDTA", Z. Anal. Chem. 276, 72 (1975).

It reports that "(the) log stability constants of the 1:1 complexes formed (Rh: reagent) were found to be 3.62 and 3.82 and the molar absorbance coefficients amount to 602 and 830 cm2 mol-1, with EDTA and CDTA respectively."

Regards,

Daniel

Hi again! You may also find this crystallographic report interesting, as it seems that rhodium(III) prefers to be pentacoordinate with respect to EDTA:

"The crystal and molecular structure of aquo(ethylenediaminetriacetatoacetic acid)rhodium(III)", Acta Cryst. (1973). B29, 1023-1030.

It refers specifically to additional references (see link below).

Regards,

Daniel

http://scripts.iucr.org/cgi-bin/paper?S0567740873003791

Thanks a lot. Great

to Thorsten Klawonn

is what your complex is colorful?

Mr. Klawonn,

Please find the data about ihermodynamic stability constant K, and the related reference:

lgK = 13.86 (RuIII-EDTA) [1]

[1] J. Byegtrd, G. Skarnemark, M. Skhlberg, The stability of some metal EDTA, DTPA and DOTA complexes: Application as tracers in groundwater studies, J. Radioanal. Nucl. Chem. 241 (1999) 281-290

@Thorsten: A structural study with EDTA-like ligands can be found here: U. Rychlewska et al. (2002) Inorg. Chim. Acta, 328 (1), 218-228. These complexes are, however, hexadentate whereas the EDTA complex is pentadentate as mentioned above.

@Bojidarka: Thorsten's request was for the EDTA complex formation constant of *rhodium(III)*, not *ruthenium(III)*. By the way, two of the names of the researchers in your reference are misspelled. They should be: (Johan) Byegård and (Mats) Skålberg. The third one, (Gunnar) Skarnemark, was correctly spelled.

http://www.sciencedirect.com/science/article/pii/S0020169301007277