Synthesis and Characterization of Octa- and Hexanuclear Polyoxomolybdate Wheels: Role of the Inorganic Template and of the Counterion
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- 作者：Anne Dolbecq ; Laurent Lisnard ; Pierre Mialane ; Jé ; rô ; me Marrot ; Marc Bé ; nard ; Marie-Madeleine Rohmer ; and Francis Sé ; cheresse
- 刊名：Inorganic Chemistry
- 出版年：2006
- 出版时间：July 24, 2006
- 年：2006
- 卷：45
- 期：15
- 页码：5898 - 5910
- 全文大小：485K
- 年卷期：v.45,no.15(July 24, 2006)
- ISSN：1520-510X
文摘
Eight new compounds based on [O3PCH2PO3]4- ligands and {MoV2O4} dimeric units have been synthesized andstructurally characterized. Octanuclear wheels encapsulating various guests have been isolated with differentcounterions. With NH4+, a single wheel was obtained, as expected, with the planar CO32- guest, (NH4)12[(MoV2O4)4(O3PCH2PO3)4(CO3)2]·24H2O (1a), while with the pyramidal SO32- guest, only the syn isomer (NH4)12[(MoV2O4)4(O3PCH2PO3)4(SO3)2]·26H2O (2a) was characterized. The corresponding anti isomer was obtained with Na+ ascounterions, Na12[(MoV2O4)4(O3PCH2PO3)4(SO3)2]·39H2O (2b), and with mixed Na+ and NH4+ counterions,Na+(NH4)11[(MoV2O4)4(O3PCH2PO3)4(SO3)2]·13H2O (2d). With [O3PCH2PO3]4- extra ligands, the octanuclear wheelLi12(NH4)2[(MoV2O4)4(O3PCH2PO3)4(HO3PCH2PO3)2]·31H2O (4a) was isolated with Li+ and NH4+ counterions andLi14[(MoV2O4)4(O3PCH2PO3)4(HO3PCH2PO3)2]·34H2O (4c) as a pure Li+ salt. A new rectangular anion, formed byconnecting two MoV dimers and two MoVI octahedra via methylenediphosphonato ligands with NH4+ as counterions,(NH4)10[(MoV2O4)2(MoVIO3)2(O3PCH2PO3)2(HO3PCH2PO3)2]·15H2O (3a), and Li9(NH4)2Cl[(MoV2O4)2(MoVIO3)2(O3PCH2PO3)2(HO3PCH2PO3)2]· 22H2O (3d) as a mixed NH4+ and Li+ salt have also been synthesized. The structuralcharacterization of the compounds, combined with a study of their behavior in solution, investigated by 31P NMR,has allowed a discussion on the influence of the counterions on the structure of the anions and their stability.Density functional theory calculations carried out on both isomers of the [(MoV2O4)4(O3PCH2PO3)4(SO3)2]12- anion(2), either assumed isolated or embedded in a continuum solvent model, suggest that the anti form is favored by~2 kcal mol-1. Explicit insertion of two solvated counterions in the molecular cavity reverses this energy differenceand reduces it to less than 1 kcal mol-1, therefore accounting for the observed structural versatility.