J. Am. Chem. Soc., ASAP Article 10.1021/ja0575934 S0002-7863(05)07593-1
Web Release Date: April 7, 2006
Copyright © 2006 American Chemical Society
A Strategy for the Analysis of Chiral Polyoxotungstates by Multinuclear (31P, 183W) NMR Spectroscopy Applied to the Assignment of the 183W NMR Spectra of 1-[P2W17O61]10- and 1-[YbP2W17O61]7-
Géraldine Lenoble, Bernold Hasenknopf, and René Thouvenot*
Contribution from the Université Pierre et Marie Curie - Paris 6, Institut de Chimie Moléculaire FR 2769, Laboratoire de Chimie Inorganique et Matériaux Moléculaires (UMR CNRS 7071), Case Courrier 42, 4 place Jussieu, 75252 Paris Cedex 05, France
Received November 21, 2005
This paper describes the complete assignment of the 183W NMR spectra of the chiral polyoxometalates 1-[P2W17O61]10- and 1-[YbP2W17O61]7- in aqueous solution. These spectra display each 17 lines of equal intensity with a relatively narrow chemical shift distribution. The identification of signals is based on selective 31P-183W decoupling and recognition of particular sets of coupling constants for tungsten atoms around the lacunary site. Further assignment is obtained by 183W 2D-COSY NMR experiments. We demonstrate herewith a new way for the unambiguous assignment of 183W NMR spectra of polyoxotungstates without any symmetry elements or tungsten atoms in special positions. This way relies on the correlation of the magnitude of 2JW-W coupling constants with the geometry of oxo-bridges in polyoxotungstates. These results open the way to monitor interaction sites of chiral polyoxotungstates with organic ligands.