Nitrosyl ion, solvation

Species 3.6 is therefore indeed a complex which, in classical terms, may be called a nitrosyl ion solvated with one molecule of water. The complex is calculated to be more stable than its fragments by 75 kJ mol-1. It is likely, as the authors say, that this calculated value is a little smaller than the true value. 

A speculative proposal was made thirty years ago by Schmid and Krenmayr77, namely that a nitrosyl ion solvated, but not covalently bonded, by a water molecule may be involved in these systems. This hypothesis was investigated theoretically in 1984 by Nguyen and Hegarty78 who carried out ab initio SCF calculations of structure and properties employing the minimal STO-3G basis set, a split-valence basis set plus polarization functions. Optimized geometries of six planar and two nonplanar forms were studied for the nitrosoacidium ion. The lowest minimum of molecular electrostatic potential... 

In summary, it is now more likely that the solvated nitrosyl ion, not the nitroso-acidium ion, is the nitrosating agent in diazotizations. 

In the preceding section we concentrated on the rate-limiting steps of diazotizations in aqueous sulfuric and perchloric acid. The results were the identification of dinitrogen trioxide and (solvated) nitrosyl ions as electrophilic reagents, aniline and anilinium ion as nucleophilic reagents and an interpretation of the influence of acidity. 

Nitrosyl chloride is associated in the liquid state. The nitrogen-chlorine bond is abnormally long (1.95 A) 34 and the [NO]+ ion is easily formed. This is assumed to be solvated by means of chlorine bridges i 22 and resonance between the following structures has been suggested ... 

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