Half-Sandwich Ruthenium(II) Complexes of Click Generated 1,2,3-Triazole Based Organosulfur/-selenium Ligands: Structural and Donor Site Dependent Catalytic Oxidation and Transfer Hydrogenation Aspects

1-Benzyl-4-((phenylthio)-/(phenylseleno)methyl)-1 H -1,2,3-triazole ( L1 / L2 ) and 4-phenyl-1-((phenylthio)-/(phenylseleno)methyl)-1 H -1,2,3-triazole ( L3 / L4 ) synthesized using the click reaction have been reacted for the first time with [{(η 6 -C 6 H 6 )RuCl(μ-Cl)} 2 ] and NH 4 PF 6 to design the half-sandwich complexes [(η 6 -benzene)Ru L Cl]PF 6 ( 1 – 4 for L = L1 – L4 ), which have been characterized by single-crystal X-ray diffraction and explored for the catalytic oxidation of alcohols with N -methylmorpholine N -oxide (NMO) and transfer hydrogenation of ketones with 2-propanol. There is a pseudo-octahedral “piano-stool” disposition of donor atoms around Ru in 1 – 4. In 1 and 2, N(3) of the triazole skeleton coordinates with Ru, whereas in other complexes the nitrogen involved is N(2). The Ru–S and Ru–Se bond distances are 2.3847(11)/2.3893(10) and 2.497(5)/2.4859(9) Å, respectively. The catalytic processes are more efficient with 3 and 4 (compared to 1 and 2 ), in which N(2) of the triazole is involved in coordination with Ru. The nature of the chalcogen and steric factors together also appear to affect the efficiency of complexes. HOMO–LUMO energy gaps are lower for 3 and 4 than for 1 and 2 . The formation of Ru IV ═O species probably results in oxidation and transfer hydrogenation involves an intermediate containing Ru–H. Bond distances and angles based on DFT calculations are generally consistent with experimental values.