Hydrogenation of 1-Octene Using Homogenous Pyrazolyl Nickel(II) Complexes as Pre-Catalysts: Experimental and Computational Studies

We present the synthesis, characterization, and catalytic activities of four bis(pyrazolyl)nickel(II) complexes (1–4) in the hydrogenation of 1-octene. Characterization techniques, such as Fourier-transform infrared spectroscopy, electrospray ionization-mass spectrometry, elemental analysis, single-crystal X-ray diffraction, and density functional theory calculations (DFT) were employed. These complexes exhibited significant catalytic activities for olefin hydrogenation under mild experimental conditions. The tert-butyl-substituted bis(pyrazolyl)nickel(II) complex 2 demonstrated the highest conversion of 1-octene to n-octane. The catalyst's recyclability was demonstrated over multiple cycles with minimal activity loss. Catalytic evaluations involved optimizing parameters such as temperature, pressure, and reaction time. Homogeneity tests confirmed the homogeneous nature of these catalytic systems. The reaction mechanism was studied using DFT calculations. The results demonstrate the efficacy of the nickel(II) complexes in enabling the hydrogenation of 1-octene.