Synthesis, Spectral and Thermo Analytical Studies of Nickel (II) and Ruthenium (II) Complexes of Schiff Base Ligands for Hydrogenation of Benzene

Abstract

Novel Nickel(II) and Ruthenium(II) complexes of schiff base ligands were synthesized and studied using various spectral and thermoanalytical techniques. One of the metal complexes [NiII (L-2)2(CH3OH)2] has been structurally characterized on the basis of X-ray data and was found to adopt a helical structure stabilized by strong intermolecular H-bonding to form a dimeric structure. The complex crystallizes in the triclinic space group P-1 with unit cell dimensions a=11.1863(13) Å, b=12.0526(16) Å, c =12.5639(14) Å, α= 112.216°, β=95.065°, γ= 105.289° and Z=2. The coordination environment around the Ni(II) ion is in distorted octahedral geometry with four donor atoms (N2O2) coming from the two ligands providing four coordination sites (two by each ligand) through two azomethine nitrogen, N1 and N2 (Ni(1)–N(1) = 2.080(5) and Ni(1)–N(2) = 2.090(5)Å and two deprotonated hydroxyl oxygen, O1 and O2 (Ni(1)–O(1) = 2.008(3) and Ni(1)–O(2) = 1.998(3)Å. The remaining two coordination sites O3 and O4 are provided by two coordinated methanol molecules (Ni(1)–O(3) = 2.093(4) and Ni(1)–O(4) = 2.154(4)Å. Stability of the complexes was determined using TG-DTA.The fluorescence quantum yield of complexes was found to be lower than that of the (L-2) (Φ=0.032). [NiII (L-2)2(CH3OH)2] was used as a catalyst in hydrogenation. Keywords: Selective hydrogenation, schiff base complex, dimeric crystal structure, hydrogen bonding network.