New low-spin Co(II) complexes with novel tripodal 1,1,1-tris(dimethylphosphinomethyl)ethane ligand: electron transfer kinetics and spectroscopic characterization of Co(II)P-6 and Co(II)P3S3 ions in aqueous solution

Citation
S. Iwatsuki et al., New low-spin Co(II) complexes with novel tripodal 1,1,1-tris(dimethylphosphinomethyl)ethane ligand: electron transfer kinetics and spectroscopic characterization of Co(II)P-6 and Co(II)P3S3 ions in aqueous solution, CAN J CHEM, 79(9), 2001, pp. 1344-1351
Citations number
36
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry
Journal title
CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE
ISSN journal
0008-4042 → ACNP
Volume
79
Issue
9
Year of publication
2001
Pages
1344 - 1351
Database
ISI
SICI code
0008-4042(200109)79:9<1344:NLCCWN>2.0.ZU;2-3
Abstract
Substitution-inert Co(II) complexes with tripodal 1,1,1-tris(dimethylphosph inomethyl)ethane were produced in aqueous solution by the controlled-potent ial electrolysis. EPR studies indicated that the Co(II)P-6 and Co(II)P3S3 s pecies are in the low-spin t(2g)(6)e(g)(1) state. The analyses of the absor ption spectra of the Co(II) species in solution indicated significant Jahn- Teller distortion in Co(II)P-6 and Co(II)P3S3 ions as expected for the low- spin d(7) electronic configuration, while less distortion was observed for the Co(II)S-6 ion. Kinetic studies of the redox reactions involving these C o(III/II) species confirmed that the electron self-exchange reactions for t he Co(III/II)P-6 and Co(III/II)P3S3 couples are relatively fast (k(ex) simi lar to 1 x 10(4) dm(3) mol(1) s(1)), which is consistent with the results f or other low-spin - low-spin Co(III/II) couples. It was concluded that the nephelauxetic effect of the P-donor atom stabilizes the low-spin state in C o(II), and that the rather rapid electron exchange rates for these Co(III/I I) couples were explained by the lack of the spin reorganization process re quired for the ordinary low-spin - high-spin Co(III/II) couples.