  The reliability of the recently proposed natural orbital functional
supplemented with second-order M{\o}ller-Plesset calculations, (NOF-MP2), has
been assessed for the mechanistic studies of elementary reactions of transition
metal compounds by investigating the dehydrogenation of water by the scandium
cation. Both high- and low-spin state potential energy surfaces have been
searched thoroughly. Special attention has been paid to the assessment of the
capability of the NOF-MP2 method to describe the strong, both static and
dynamic, electron correlation effects on the reactivity of Sc+(3D,1D) with
water. In agreement with experimental observations, our calculations correctly
predict that the only exothermic products are the lowest-lying ScO+(1\Sigma)
and H2(1\Sigma_g+) species. Nevertheless, an in-depth analysis of the reaction
paths leading to several additional products was carried out, including the
characterization of various minima and several key transition states. Our
results have been compared with the highly accurate multiconfigurational
supplemented with quasi degenerate perturbation theory, MCQDPT,
wavefunction-type calculations, and with the available experimental data. It is
observed that NOF-MP2 is able to give a satisfactorily quantitative agreement,
with a performance on par with that of the MCQDPT method.
