Herein, a new pincer-like amino phosphine donor ligand, H2L1, and its phosphine-oxide analog, H2L2, were synthesized. Subsequently, cobalt(II) complexes 1 and 2 were synthesized by the reaction of anhydrous Co(II)Cl2 with ligands H2L1 and H2L2, respectively. The ligands and complexes were fully characterized by various physicochemical and spectroscopic characterization techniques. Finally, the identity of the complexes 1 and 2 was confirmed by single crystal X-ray structure determination. The phosphine ligand containing complex 1 was converted to the phosphine oxide ligand containing complex 2 in air in acetonitrile solution. Both complexes 1 and 2 were investigated as precatalysts for alcohol dehydrogenation-triggered synthesis of imines in air. The phosphine-oxide complex 2 was more efficient than the phosphine complex 1. A wide array of alcohols and amines were successfully reacted in a mild condition to result in imines in good to excellent yields. Precatalyst 2 was also highly efficient for the synthesis of varieties of quinolines in air. As H2L2 in 2 has side arms that can be deprotonated, we investigated complex 2 for its base (KOtBu) promoted deprotonation events by various spectroscopic studies and DFT calculations. These studies have shown that mono deprotonation of the amine side arm attached to the pyridine is quite feasible, and deprotonation of complex 2 leads to a dearomatized pyridyl ring containing complex 2a. The mechanistic investigations of the catalytic reaction, by a combination of experimental and computational studies, have suggested that the dearomatized complex, 2a acted as an active catalyst. The reaction proceeded through the hydride transfer pathway. The activation barrier of this step was calculated to be 26.5 kcal/mol, which is quite consistent with the experimental reaction temperature under aerobic conditions. Although various pincer-like complexes are explored for such reactions, phosphine oxide ligand-containing complexes are still unexplored.