Alkoxo Bound Monooxo- and Dioxovanadium(V) Complexes: Synthesis, Characterization, X-ray Crystal Structures, and Solution Reactivity Studies

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• 作者：Gebray Asgedom ; Alavattam Sreedhara ; Jussi Kivikoski ; Jussi Valkonen ; Erkki Kolehmainen ; and Chebrolu P. Rao
• 刊名：Inorganic Chemistry
• 出版年：1996
• 出版时间：September 11, 1996
• 年：1996
• 卷：35
• 期：19
• 页码：5674 - 5683
• 全文大小：269K
• 年卷期：v.35,no.19(September 11, 1996)
• ISSN：1520-510X

文摘

A large variety of oxovanadium(V) complexes, mononuclearVOB>2⁺ and VO³⁺ in addition tothe dinuclear VO³⁺,of the structural type (VOL)₂, (VOHL)₂, VOLHQ,K(VO₂HL), K(VO₂H₂L), or(salampr) (VO₂L) {where L =Schiff base ligand possessing alkoxo group(s); HQ =8-hydroxyquinoline; salampr = cation of reduced Schiffbase derived from salicylaldehyde and 2-amino-2-methylpropan-1-ol},bound to alkoxo, phenolate and iminegroups have been synthesized in high yields and characterized byseveral spectral and analytical methods, includingsingle crystal X-ray studies. While the mononuclearVO₂⁺ complexes have been synthesized atalkaline pH, thedinuclear VO³⁺ complexes have been synthesized underneutral conditions using alkoxo rich Schiff base ligands.The X-ray structures indicate that the cis-dioxo complexes showedlonger V-O_alkoxo bond lengths compared tothe monooxo counterparts. The plot of V-O_phen bonddistances of several VO³⁺ complexes vs the lmctshoweda near linear correlation with a negative slope. The cyclicvoltammograms revealed a reversible V(V)/V(IV)couple with the reduction potentials increasing to more negative onesas the number of alkoxo groups bound toV increases from 1 to 2. Moreover, the cis-dioxoVO₂⁺ complexes are easier to reduce thantheir monooxocounterparts. The solution stability of these complexes wasstudied in the presence of added water (1:4, water:solvent), where no decomposition was observed, unlike other Schiff basecomplexes of V. The conversion of thedioxo complexes to their monooxo counterparts in the presence ofcatalytic amounts of acid is also demonstrated.The reactivity of alkoxo bound V(V) complexes is also reported.X-ray parameters are as follows.H₄L³:monoclinic space group, P2₁/c;a = 10.480(3), b = 8.719(6),c = 12.954(8) Å; mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 101.67(4)mages/entities/deg.gif">;V = 1126(1) ų;Z = 4; R = 0.060, R_w= 0.058. Complex 1: monoclinic space group,P2₁/n; a =12.988(1), b = 9.306(2), c=19.730(3) Å; mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 99.94(1)mages/entities/deg.gif">; V =2348.9(7) ų; Z = 4; R =0.031, R_w = 0.027. Complex2: monoclinic spacegroup, P2₁/n; a =12.282(3), b = 11.664(2), c =12.971(4) Å; mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 97.89(2)mages/entities/deg.gif">; V =1840.5(8) Å; Z = 4; R =0.035, R_w = 0.038. Complex5: monoclinic space group,P2₁/c; a =17.274(2), b = 6.384(2), c =16.122(2) Å;mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 116.67(1)mages/entities/deg.gif">; V = 1588.7(7)ų; Z = 4; R = 0.039,R_w = 0.043. Complex 8:monoclinic space group,P2₁/c;a = 11.991(1), b = 11.696(4),c = 12.564(3) Å; mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 110.47(1)mages/entities/deg.gif">;V = 1650.8(8) ų; Z = 2;R = 0.045, R_w =0.049.