Raman and infrared spectra of aqueous solutions of vanadates have been studied from pH 8 to > 14, and assignments are proposed for the vibrational frequencies of (Vo4)3-, (HV0,)2-, (V207)4-, (HV207)3-, and (V03),,,,-. Itappears that there is tetrahedral co-firdination of the vanadium in all these tows.

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Raman and infrared spectra have been measured of solutions of oxides of metals of Groups VIA, VA, and IVA in aqueous hydrofluoric, hydrochloric, and perchloric acids. Evidence was obtained for the existence in such solutions of fluoro-and chloro-complexes of molybdenum and tungsten with cis-dioxo-ligands, of mono-oxo-pentahalogeno-species of niobium and vanadium, and of unsubstituted halogeno-complexes of tantalum, titanium, zirconium, and hafnium. Polynuclear complexes were formed in perchloric acid solutions.MOST of the highest-valency oxides of early transition metals will, when freshly prepared, dissolve easily in strong mineral acids, but little is known concerning the constitutions or structures of the solute species. The Raman technique is in principle well suited t.o the investigation of this problem as the solutions are usually colourless or pale yellow, and oxy-species give intense and characteristic Raman 1ines.l Hydrofluoric and hydrochloric acids were chosen because they do not give strong Raman spectra of their own, and fluoride and chloride ions are good ligands for the stabilising of high oxidation states; perchloric acid was used since the perchlorate ion, which has a very simple Raman spectrum, is unlikely to co-ordinate to the metals.The various species which we postulate from these

The structures of a number of Deroxvoxalates of elements of Group VIA, VA, and IVA have been studied by means of the infrared and Raman spectra of ;he solids.TRANSITION-METAL peroxy-complexes are most readily formed by the elements of Groups VIA. VA, and IVA, and for these the stablest species of this type usually involve other electronegative ligands such as oxide, hydroxide, fluoride, sulphate, or oxalate. The best characterised complexes are the peroxyfluorides, which take the form [M(O,)F,]"-[M = Ti, Zr, Nb, Ta; (0,) denotes a co-ordinated peroxide group], [MO(O,)F,I2-(M = Mo, W), and [MOO(O,),F~]~-; all of these appear to be seven co-ordinate if it is assumed that the peroxide group functions as a bidentate ligand.lJ2 The aim of this research was to ascertain whether the peroxyoxalates, a large number of which have been reported,3 are of the same form: up to now, no structural measurements on these compounds has been available.The complexes are not very soluble in water and appear to be extensively dissociated in aqueous solution 2 * 4 so that spectroscopy of the solutions was not attempted. The infrared spectra of all the reported peroxyoxalates were however measured as mulls, and by using excitation from the mercury arc a t 4358 and 5461 A, the Raman spectra of crystalline samples of all but the deeply coloured titanium and uranium salts were recorded. In all cases the spectra suggest that the oxalate ligands are bidentate by comparison with the results of infrared studies on a wide range of transition-metal oxalatocomplexes and the Raman spectra of tris-oxalatocomplexes of Group III.6 The assignments and descriptions of the oxalate modes in Table 1 follow those adopted in these publications.5r6 In addition to the oxalate bands, infrared vibrations appear near 850 and 600 cm.-l which we assign to vibrations of the coordinated peroxy group l p 2 and, in some cases, strong infrared and Raman bands appear above 900 cm.-l which we assign to metal-oxygen (double bond) stretching vibrations. The Raman-active vibrations of the oxalate groups are weak for these samples (only the v4 mode is consistently observed) and thus the (M=O) stretching vibrations are easily distinguished as these are strong in the Raman on account of the large polarisability changes involved.