First water soluble Mo24+ compounds spanned by four α-hydroxycarboxylate anions

The preparation of three water soluble compounds having quadruply bonded dimolybdenum units bridged by the biologically relevant glycolate, glycerate and glyoxalate anions is reported here. All three compounds are diamagnetic, as shown by the sharp signals in the 1H NMR spectra which are consistent with the presence of multiple metal–metal bonds. The simplicity of these spectra is indicative of the presence of very symmetrical molecules in solution. Indeed, Mo2(glycolate)4·2H2O,1·2H2O, has a paddlewheel structure with a Mo–Mo distance of 2.103(1) Å. In the solid state, this compound is stabilized by an extensive array of hydrogen bonded interactions in which all hydroxyl hydrogen atoms participate.