Anhydrous Metal Nitrates

Hence dinitrogen tetroxide (sometimes mixed with an organic solvent) can be used to prepare anhydrous metal nitrates (many heavy metal nitrates are hydrated when prepared in aqueous solution, and they cannot be dehydrated without decomposition). 

N2O4 has been extensively studied as a nonaqueous solvent system and it is uniquely useful for preparing anhydrous metal nitrates and nitrato complexes (p. 468). Much of the chemistry can be rationalized in terms of a selfionization equilibrium similar to that observed for... 

Such reactions provide an excellent route to anhydrous metal nitrates, particularly when metal bromides or iodides are used, since then the nitrosyl halide decomposes and this prevents the possible... 

Anhydrous metal nitrates. C. C. Addison and N. Logan, Prep. Inorg. React., 1964,1,141-164 (62). 

Several publications on anhydrous metal nitrate chemistry describe the properties and reactions of these and related compounds. ... 

The paper discusses two types of reaction involving metal complexes, and it is postulated that each proceeds by an initial free-radical step. In reactions between metal carbonyls and N2O4—NO2 mixtures, the nature of the product depends upon the phase in which the reaction is carried out. In the liquid phase, where the predominant equilibrium is N204 N0+ + NO3-, metal nitrates or carbonyl nitrates are formed in the gas phase, where the equilibrium is N2O4 2NO2/ nitrites or their derivatives are produced. Reactions of Mn2(CO) o Fe(CO)5, Co2(CO)3, and Ni(CO)4 are discussed. Anhydrous metal nitrates in which the nitrate group is covalently bonded to the metal have enhanced reactivity. This is believed to result from the dissociation M—O—N02 M—O + NO2 This can explain the solution properties of beryllium nitrates, and the vigorous (even explosive) reaction of anhydrous copper nitrate with diethyl ether. 

Covalent bonding of the nitrate group to a metal atom normally occurs only in the absence of water. Recent work on anhydrous metal nitrates has been concerned with both structure and chemical reactivity and it is now coming to be realized that these two aspects are closely interlinked. Generalizing, we may say that the stronger the covalent bond, the more reactive is the metal nitrate. Furthermore, extreme covalency leads to volatility (as with the volatile copper nitrate) and those nitrates which display volatility are also the most reactive chemically. 

Just as hydrolysis of a compound may occur in water (see Section 6.7), solvolysis such as reaction 8.76 can take place in liquid N2O4. Such reactions are of synthetic importance as routes to anhydrous metal nitrates. 

The spectra of anhydrous metal nitrates such as Zn(N03)2 [719] and U02(N03)2 [720] can be interpreted in terms of C2V symmetry since the NO3 group is covalently bonded to the metal. Raman spectra of metal nitrates in the molten state [721,722] indicate that the degeneracy of the V3 vibration is lost and the Raman-inactive V2 vibration appears. Apparently, the D3 , selection rule is violated because of cation-anion interaction. 

Nitrate Compounds and Complexes Addison, C. C., and N. Logan, Adv. Inorg. Chem. Radiochem., 1964, 6, 72 (anhydrous metal nitrates). 

The general area of anhydrous metal nitrates has been surveyed by Addison (10). The anhydrous tetranitrate has been prepared (176) by the reaction of dinitrogen pentoxide on zirconium tetrachloride at 30°C. Nitryl chloride is evolved and an initial product of composition Zr(NO3)4-0.4N2O5 0.6N2O4 is obtained. The nitrogen oxides can be... 

The use of far-infraired spectra to distinguish unidentate and bidentate nitrato coordination has been controversial. Nuttall and Taylor " suggested that unidentate and bidentate complexes exhibit one and t vo MO stretching bands, respectively, in the 350-250 cm" region. Bullock and Parrett sho ved, however, that such a simple rule is not applicable to many known nitrato complexes. Ferraro and Walker assigned the MO stretching bands of anhydrous metal nitrates such as Cu(N03)2 and PrCNOa),. 

When metals or metal compounds react with N2O4 in the synthesis of anhydrous metal nitrates the first products which usually separate out, frequently in crystalline form, are metal nitrate-N204 adducts. Much speculation has centred around the role of the N2O4 in the crystal lattice, A preliminary report has now appeared of the crystal structure of the copper... 

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