Dinuclear Oxovanadium(IV) N-(Phosphonomethyl)iminodiacetate Complexes: Na4[V2O2{(O)2P(O)CH2N(CH2COO)2}2]&
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- 作者：Debbie C. Crans ; Feilong Jiang ; Oren P. Anderson ; and Susie M. Miller
- 刊名：Inorganic Chemistry
- 出版年：1998
- 出版时间：December 28, 1998
- 年：1998
- 卷：37
- 期：26
- 页码：6645 - 6655
- 全文大小：190K
- 年卷期：v.37,no.26(December 28, 1998)
- ISSN：1520-510X
文摘
The dioxovanadium(IV) complexes with pida4- ligands (H4pida) = N-(phosphonomethyl)iminodiacetic acid),Na4[V2O2{(O)2P(O)CH2N(CH2COO)2}2]·10H2O (1) and Na8[V2O2{(O)2P(O)CH2N(CH2COO)2}2]2·16H2O (2), wereisolated from reactions of H4pida with either oxovanadium(V) (i.e., NaVO3) or oxovanadium(IV) precursors withinthe pH range of 2-8. The structures of complexes 1 and 2 were investigated by X-ray diffraction methods andin contrast to expectation were both found to be dinuclear. Complex 1 crystallized in the monoclinic system:P21/n, a = 10.5632(1) Å, b = 11.1868(1) Å, c = 12.6921(1) Å, 
= 106.45
, V = 1438.44(2) Å3, Z = 4, and R(wR2) = 0.0781 (0.2017). Complex 2 crystallized in the monoclinic system P21/c: a = 13.9822(2) Å, b = 11.1888(2) Å, c = 18.6519(3) Å, = 100.88, V = 2865.51(8) Å3, Z = 4, and R (wR2) = 0.046 (0.125). Both complexes1 and 2 have similar dimeric frameworks where two vanadium centers are linked by two phosphonate groups oftwo pida4- ligands (quadridentate binucleating), bridging through their four oxygen atoms to form a V2O4P2eight-membered ring which possesses a crystallographic inversion center. In contrast to their solid-state features,in aqueous solution both dinuclear crystalline compounds immediately dissociate to monomeric species, as observedby EPR and UV/vis spectroscopy. Both solution-state EPR and NMR spectroscopy confirmed that redox chemistryis involved in the reaction between vanadate and H4pida. Studies in mixed solvent systems showed that the dinuclearcomplex would remain intact in the presence of sufficient organic solvent. In the absence of oxygen the mononuclearand the dinuclear complexes will reversibly interconvert, whereas, in the presence of oxygen, the complexes willoxidize. These studies document the existence of higher oligomeric vanadium compounds and surprisingly, ingeneral, lend credibility to several emerging mechanistic proposals involving oligomeric species of vanadiumcompounds in catalytic processes.
= 106.45, V = 1438.44(2) Å3, Z = 4, and R(wR2) = 0.0781 (0.2017). Complex 2 crystallized in the monoclinic system P21/c: a = 13.9822(2) Å, b = 11.1888(2) Å, c = 18.6519(3) Å, = 100.88, V = 2865.51(8) Å3, Z = 4, and R (wR2) = 0.046 (0.125). Both complexes1 and 2 have similar dimeric frameworks where two vanadium centers are linked by two phosphonate groups oftwo pida4- ligands (quadridentate binucleating), bridging through their four oxygen atoms to form a V2O4P2eight-membered ring which possesses a crystallographic inversion center. In contrast to their solid-state features,in aqueous solution both dinuclear crystalline compounds immediately dissociate to monomeric species, as observedby EPR and UV/vis spectroscopy. Both solution-state EPR and NMR spectroscopy confirmed that redox chemistryis involved in the reaction between vanadate and H4pida. Studies in mixed solvent systems showed that the dinuclearcomplex would remain intact in the presence of sufficient organic solvent. In the absence of oxygen the mononuclearand the dinuclear complexes will reversibly interconvert, whereas, in the presence of oxygen, the complexes willoxidize. These studies document the existence of higher oligomeric vanadium compounds and surprisingly, ingeneral, lend credibility to several emerging mechanistic proposals involving oligomeric species of vanadiumcompounds in catalytic processes.