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

Abstract

1-Benzyl-4-((phenylthio)-/(phenylseleno)methyl)-1H-1,2,3-triazole (L1/L2) and 4-phenyl-1-((phenylthio)-/(phenylseleno)methyl)-1H-1,2,3-triazole (L3/L4) synthesized using the click reaction have been reacted for the first time with [{(η6-C6H6)RuCl(μ-Cl)}2] and NH4PF6 to design the half-sandwich complexes [(η6-benzene)RuLCl]PF6 (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 RuIV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.

Computational investigations of click-derived 1,2,3-triazoles as keystone ligands for complexation with transition metals: a review

“…In conclusion, the electronic stability of complexes involving N(1) in coordination was greater than in those involving N(2) and so their reactivity is less. 37,56,126,208 It should be noted that the crystallographical structural data for complexes 46, 47, and 48 were in good agreement with the calculated values.…”

“…57 It was shown that in the following Pd complexes, the calculated electron densities at Se, Pd, and N(3) of the triazole ring were higher in complex 16 than in complex 15, mainly due to the strong metal-ligand interaction in complex 16 and its subsequent higher stability and lower reactivity relative to complex 15. 37,56,126 Moreover, in these complexes, there was a good agreement between the experimentally observed and calculated bond distances and angles. However, some of calculated Pd-M bond distances (M ¼ S/Se) deviated from the corresponding observed ones.…”

“…This electronic feature can be interpreted as due to a strong coordination between N(1) of triazole and Ru in complexes 52 and 53, which leads to greater electronic stability in comparison with 54 and 55. 37 In another work, the crystal structure of Ru(II) complexes with NNN, NCN, NCN-NO 2 , NCN-F, and NCN-Tph ligands were determined via the X-ray diffraction method and some considerable changes were observed attributed to the packing effects, such as a strong distortion within RuNCN-F.…”

On Water Cu@g‐C3N4 Catalyzed Synthesis of NH‐1,2,3‐Triazoles via [2+3] Cycloadditions of Nitroolefins/Alkynes and Sodium Azide

“…Development of sustainable protocols for the synthesis of 1,2,3‐triazole scaffolds have emerged one of the thrust area of research for organic chemist due to their exclusive pharmaceutical, agrochemical, medicinal and many other applications . Several strategies have been reported for the synthesis of 1,2,3‐triazoles and Huisgen's dipolar cycloaddition of organic azides and alkynes is the most straightforward route .…”

1H‐1,2,3‐Triazole: From Structure to Function and Catalysis

“…Singh and co‐workers prepared a series of ruthenium catalysts ( 44–47 ), which they used for the oxidation of primary and secondary alcohols (in the presence of N ‐methylmorpholine N ‐oxide) and for the hydrogenation of ketones (Scheme ) . The catalysts, in which the N2 atom is bound to ruthenium ( 46 , 47 ), were shown to be more efficient than those involving N3–metal coordination.…”