ISSN:
0009-2940
Keywords:
Vanadium
;
Haloperoxidase
;
Schiff bases
;
Diethanolamine
;
Water ligation
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Reaction of vanadyl sulfate with the Schiff base H2L1 derived from o-vanillin and glycine leads to [VIVO(H2O)L1 (1), treatment of which with acetyl chloride affords cis-[VIVCl2L1] (2). Reaction of [VO(acac)2] with the Schiff base H2L2 derived from o-hydroxynaphthaldehyde and o-hydroxyaniline under aerobic conditions yields [{VVO(L2)}2μ-O] (3), which undergoes methanolysis in excess methanol to form [VVO(MeOH)(OMe)L2] (5a). Complex 5a is also obtained via [VVOCl(L2)] (4) and MeOH. On treatment of 3 with an equimolar amount of ethanol, [VVOCl(L2)] (4) and MeOH. On treatment of 3 with an equimolar amount of ethanol. [VVO(OEt)L2] (5b) is obtained. With the chiral tertiary bis(ethanol)amine (S)- or (R)-(HOCH2CH2)2NCH(Ph)Me, H2L3, [VO(acac)2] loses only one acetylacetonate (1-) ligand, and the complexes (S)- and (R)-[VVO(acac)L3] (6a) are formed. As is evident for the corresponding reaction with (HOCH2CH2)2NPh, H2L4, which affords [VVO(acac)L4 (6b), the substitution is a second-order process (rate constant 0.013 M-1 h-1). 5a…MeOH, 5b, (R)-6a, and (S)-6a have been structurally characterized by single crystal X-ray diffraction analysis. The molecular connectivities have also been established for 1-H2O. All of the structurally characterized complexes contain an O*O3N donor set (O* denotes a doubly-bonded oxo group) and thus model the coordination environment of the active site in vanadate-dependent haloperoxidases. This model character is particularly pronounced in 5b, the coordination geometry of which is half-way to trigonal-bipyramidal. 5a and 6a contain, in addition to the O*O3N set, a labile V-O or V-N bond, respectively, which may mimic substrate binding to the active centre. 6a is also of relevance to the enantioselective peroxide oxidation of sulfides to sulfoxides by catalyst systems containing vanadium and H2L3.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19971300517
