Multiconfiguration self-consistent-field and configuration interaction calculations of the potential energy surfaces were performed for the mildly exoergic reaction, Ti+NO-->TiO+N and the largely exoergic reaction, Ti+O-2-->TiO+O. The end-on approach appears to be most efficient for the Ti+NO reaction, while the side-on one is favored for the Ti+O-2 reaction. Both reactions have activation barriers in the initial collision phase. Two stable forms of the intermediates were found for the first reaction in agreement with a recent density functional study, which can be represented as NTiO with an obtuse NTiO angle and Ti[NO] with an acute NTiO angle. The former isomer is calculated to be more stable than the latter. Similarly, two stable isomers were found for the second reaction, namely OTiO and Ti[O-2], the former being more stable than the latter. We describe here the general shape of the potential energy surfaces involving these intermediates and their implication on reaction mechanism. The electron transfer from the metal atom to the ligand occurs at short intermolecular distances.