Knowledge Bank

The infrared spectra of nickel, palladium and titanium mononitrosyl isolated in solid argon at low temperature have been reinvestigated. Two kinds of mechanisms of reactions metal-NO have been observed: In the $Ni+NO$ and $Pd+NO$ experiments, concentration and photochemical studies demonstrate the existence of two isomeric forms of NiNO and only one isomeric form of PdNO with a bent structure. In the NiNO complex case, analyses of the $\mathrm{<mrow\; data-mjx-texclass="ORD">58</mrow>}Ni/60Ni$, $\mathrm{<mrow\; data-mjx-texclass="ORD">14</mrow>}N/15N$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">16</mrow>}O/18O$ isotopic effects indicate that a first form has an end-on bent configuration (as with palladium), and a second form has a cyclic structure, in which the NO ligand is significantly more perturbed. Reversible conversion is achieved by photo selective UV-Visible excitation. In the $Ti+NO$ experiments, no side-bonded TiNO form has been observed and insertion reaction doesn't need any appreciable activation energy. All three modes of the $N-Ti-O$ insertion product are detected. Comparisons between the $Ni+NO$, $Pd+NO$ and $Ti+NO$ systems are presented. Density Functional calculations of the geometrical, electronic and vibrational properties of these isomers are also presented and compared to the experimental values. Isomerization energies have been estimated.