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Complex formation of vanadium(IV) with 1,3,5-triamino-1,3,5-trideoxy-cis-inositol and related ligands

Morgenstern, Bernd and Steinhauser, Stefan and Hegetschweiler, Kaspar and Garribba, Eugenio and Micera, Giovanni and Sanna, Daniele and Nagy, László (2004) Complex formation of vanadium(IV) with 1,3,5-triamino-1,3,5-trideoxy-cis-inositol and related ligands. Inorganic Chemistry, Vol. 43 (10), p. 3116-3126. eISSN 1520-510X. Article.

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DOI: 10.1021/ic0352046

Abstract

The complex formation of vanadium(IV) with 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci) and 1,3,5-trideoxy-1,3,5-tris(dimethylamino)-cis-inositol (tdci) was studied in aqueous solution and in the solid state. The formation constants of [VIVO(taci)]2+, [VIVO(tdci)]2+, and [VIV(tdci)2]4+ and of the deprotonation product [VIV(tdci)2H-1]3+ were determined (25 °C, 0.1 M KNO3). Cyclic voltammetry measurements established a reversible one-electron transfer for the [VIV(tdci)2H-m](4-m)/[VIII(tdci)2H-n](3-n) couple (0 ≤ n, m ≤ 6) with a strongly pH-dependent E1/2 obs (+0.15 V at pH 5, −0.57 V at pH 13.5). Slightly more negative potentials were measured for the taci complexes. An additional quasi-reversible electron transfer at strongly positive potentials (1.2−0.5 V) was assigned to the [VV(taci)2H-m](5-m)/[VIV(taci)2H-n](4-n) couple. The structures of [VIV(taci)2](SO4)2•12H2O (1), [VIV(tdci)2][V4VO12]•14.5H2O (2), and [VIV(tdci)2H-1]Cl3•15H2O (3) were determined by single-crystal X-ray analysis. The cations of 1−3 exhibit a structure of approximate D3d symmetry. The vanadium centers have an almost regular octahedral geometry. The coordinated oxygen donors are deprotonated, and their protons are transferred to the amino groups which act as internal bases. For both ligands, EPR measurements support the formation of non-oxo VIV complexes, with a dz2 ground state, in aqueous solution above pH 7. The spectral features are indicative of hexacoordinated complexes with a geometry distorted toward a trigonal prism. Finally, a mechanism is proposed for the decomposition of [VIVL2H-x](4-x) (L = taci and tdci) in strongly alkaline media (pH ≈13).

Item Type:Article
ID Code:1476
Status:Published
Refereed:Yes
Uncontrolled Keywords:Vanadium(IV), cyclic voltammetry, X-ray analysis
Subjects:Area 03 - Scienze chimiche > CHIM/03 Chimica generale e inorganica
Divisions:001 Università di Sassari > 01 Dipartimenti > Chimica
002 Altri enti e centri di ricerca del Nord Sardegna > CNR-Consiglio Nazionale delle Ricerche > Istituto di chimica biomolecolare, Sassari
Publisher:American Chemical Society
eISSN:1520-510X
Deposited On:18 Aug 2009 10:05

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