Zur Redoxchemie und Struktur von Oxovanadium(IV,V)-KompIexen mit substituierten Dibenzotetraaza[14]annulen Liganden Redox Chemistry and Structure of Oxovanadium(IV.V) Complexes Containing Substituted Dibenzotetraaza[14]annulene Ligands
نویسنده
چکیده
The oxovanadium(IV) complexes LVO and L'VO (L = dianion of 5,14-dihydro-6,8,15.17tetramethyldibenzo[b.i][l,4.8,ll]tetraazacyclotetradecine. H2L. and L' = dianion of 5.14-dihydro-6,15-dimethyl-8,17-diphenyldibenzo[b,i][l,4,8,1 l]tetraazacyclotetradecine, H2L') are redox active as indicated by cyclovoltammetric measurements and confirmed by preparative methods: Reversible oxidation to the corresponding oxovanadium(V) cations is observed at ca. 0.35 V vs. SCE in CH2C12, and these cations are prepared in high yield by oxidation of the oxovanadium(IV) precursors with [(CsH5)2Fe]SbF6 (reversible by addition of cobaltocene). Irreversible reduction waves are observed for both complexes in the range -1 .9 to 2.1 V vs. SCE in CH2C12. Preparative reduction of LVO with Na/K alloy affords very unstable anionic oxovanadium(IV) complexes containing a deprotonated or reduced ligand, while with Li[B(C2H5)3H] in THF the Lewis acid/Lewis base adduct L V O xB(C 2H3)3 is isolated. Spec troscopic data including ESR [vanadium(IV)] and 51V NMR [vanadium(V)] are given and discussed. The complexes LVO and [LVO]SbF6 have been characterized by single crystal Xray structure determinations.
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