ISSN:
1572-8927
Keywords:
Protonation of metal complex
;
aminopolyphosphonate complexes
;
scandium yttrium-, and lanthanoid-NTMP complexes
;
scandium-, yttrium-, and lanthanoid-EDTMP complexes
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The protonation equilibria of nitrilotris(methylenephosphonic acid) (NTMP, H6L) and ethylenediaminetetrakis(methylenephosphonic acid) (EDTMP, H8L) complexes of scandium, yttrium, and lanthanoids have been studied potentiometrically at 25°C and at an ionic strength of 0.1 mol-dm−3 KNO3. The first protonation constants of NTMP complexes of lanthanoids, K MHL , decrease with decreasing of the ionic radius of the lanthanoid [log K MHL =7.82 (La3+) −6.90 (Lu3+)] and show a so-called “Tetrad effect”. The second protonation constants, K MH 2L, change very little with the lanthanoid metal ions (logK MH 2L=5.3−5.7). These results suggest that, in the first protonation process in ML, the proton attacks the nitrogen of NTMP rupturing the M-N of M(ntmp)3−. The pattern of the change in the protonation constants of the EDTMP complexes with the atomic number of the lanthanoid is quite different from that of the NTMP complexes. This fact indicates that the manner of protonation of the EDTMP complexes differs from that of NTMP complexes. The protonation constants of yttrium complexes of NTMP and EDTMP agree with those of lanthanoid complexes, whereas those of scandium complexes deviate from the values predicted from its ionic radius.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00675114
Permalink
