Synthesis and Structures of Ruthenium Carbonyl Complexes Bearing Pyridine-Alkoxide Ligands and Their Catalytic Activity in Alcohol Oxidation

Abstract

Reaction of Ru 3 (CO) 12 with two equiv of 6-bromopyridine alcohols 6-bromopyCHROH [(R = C 6 H 5 ( L1 ); R = 4-CH 3 C 6 H 4 ( L2 ); R = 4-OMeC 6 H 4 ( L3 ); R = 4-ClC 6 H 4 ( L4 ); (R = 4-CF 3 C 6 H 4 ( L5 ); R = 2-OMeC 6 H 4 ( L6 ); R = 2-CF 3 C 6 H 4 ( L7 )] and 6-bromopyC(Me) 2 OH ( L8 ) in refluxing xylene afforded novel trinuclear ruthenium complexes [6-bromopyCHRO] 2 Ru 3 (CO) 8 ( 1a-1g ) and [6-bromopyC(Me) 2 O] 2 Ru 3 (CO) 8 ( 1h ). These complexes were characterized by FT-IR and NMR spectroscopy as well as elemental analysis. The structures of all the complexes were further confirmed by X-ray crystallographic analysis. In the presence of tert -butyl hydroperoxide (TBHP) as the source of oxidant, complexes 1a - 1h displayed high catalytic activities for oxidation of primary and secondary alcohols and most of oxidation reactions could be completed within 1 h at room temperature.

Synthesis and Characterization of 3‐(Aryl azo)‐4‐hydroxy‐1,2‐naphthoquinone Ruthenium(III) Complexes as Catalysts for Benzyl Alcohol Oxidation

“…It is always important to compare the results of the new work with those already published work to evaluate the novelty of the work. Therefore, efforts are made to compare the results of this article with those already published papers [15–28,42] . In this protocol, the yields of acids were comparable with those reported by Sarkar et al [42] .…”

“…It is interesting to mention here that among them ruthenium‐based catalysts are considered as the best ones because of their significant activities, [15–20] high efficiency and selectivity [21–23] . A series of substituted benzyl alcohol are catalytically oxidized to their acids by refluxing them with Ru 3 (CO) 8 (C 5 H 4 NCO 2 ) 2 complex in the aqueous isopropanol at 98 °C for 14 h [17] . Thangavel et al [24] .…”

“…As per the authors, the reported method showed many advantages such as the requirement of a small amount of catalyst and selectivity. Yan et al [27] . synthesized 6‐bromopyCHRO] 2 Ru 3 (CO) 8 and [6‐bromopyC(Me) 2 O] 2 Ru 3 (CO) 8 complexes and characterized by FT‐IR, NMR and X‐ray crystallography.…”

Selective oxidation of C (sp3)—H bonds enabled by ruthenium clusters containing pyridine‐alkoxide ligands

“…[ 29 ] Recently, our group found the carbonyl ruthenium complexes bearing pyridine‐alkoxide ligands, obtained by chelating Ru 3 (CO) 12 with 6‐bromopyridine alcohols, exhibited excellent catalytic activity in the oxidation of both primary and secondary alcohols. [ 30 ]…”

“…[29] Recently, our group found the carbonyl ruthenium complexes bearing pyridine-alkoxide ligands, obtained by chelating Ru 3 (CO) 12 with 6-bromopyridine alcohols, exhibited excellent catalytic activity in the oxidation of both primary and secondary alcohols. [30] The chelation effect of pyridine-alcohol ligands motivated us to explore the structural modification of the triruthenium unit by varying the nature and length of the side chain of the pyridine-alkoxide ligands. Herein, we report four…”