Bond Homolysis of Metal Nitrites and Nitrates

Metal nitrates readily undergo bond homolysis to form metal oxides. A survey of the CID reactions of metal nitrate anions, [Metal (N03)x+i] , with different oxidation states (x = 1-3) revealed the following competing fragmentation pathways NO2 loss to form a metal oxide (Eq. (6.85)), NO3 loss with reduction of the metal center (Eq. (6.86)), formation of the nitrate anion, N03 (Eq. (6.87)), and loss of two NO2 neutrals (Eq. (6.88)). An examination of Table 6.2 reveals that the types of reactions observed depend on both the metal and its oxidation state. For the two metals (Cu and Fe) that were studied in two different oxidation states, CID of the higher oxidation state results in NO3 loss with reduction of the metal to the lower oxidation state (Eq. (6.86)). This reaction does not occur for the lower oxidation state, which instead gives N—O bond homolysis via loss of NO2 (Eq. (6.85)). 

Although the ion-molecule reactions of the metal-oxo anions were not examined, the CID reactions of [Fe(0)(N03)3] and [Ee2(O)(N03)5] were examined. Both of these anions undergo multiple losses of NO2 (Eqs. (6.89)-(6.93)), representing access to anions with multiple 0x0 ligands.  

ESI/MS of uranium nitrate produces a wide range of cations and anions [95]. CID of anions with coordinated nitrates proceeds via sequential NO2 loss (Eqs. (6.94) and (6.95)). The only CID product that reacts with D2O is [U02(0)(N03)2] (Eq. (6.96)). 

Finally, the route to metal oxide cations from metal nitrate complexes can involve multistep reactions. For example, under harsh electrospray conditions (raised cone voltages) of aqueous iron nitrate solutions, FeO can be formed [98]. CID reactions of various precursor ions suggest that the likely reactions that lead to this ion involve NO2 loss to form the dihydroxide (Eq. (6.115)), which then undergoes water loss (Eq. (6.116)). 

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