Chalcogen (S/Se) Ligated Palladium(II) Complexes of Bulky Ligands: Application in O‐Arylation of Phenol

Abstract

Two N-pyrene based ligands L1 (1-pyrene-CH=N(CH 2 ) 2 -SPh) and L2 (1-pyrene-CH=N(CH 2 ) 2 -SePh) with an imine functionality and a chalcogen donor have been synthesized and characterized using 1 H as well as 13 C NMR spectral techniques. Palladium(II) complexes (1; PdCl 2 À ĸ 2 À L1 and 2; PdCl 2 À ĸ 2 À L2) of L1 and L2 have been prepared, isolated and characterized using NMR and single crystal X-ray diffraction studies. The geometry around Pd is nearly square planar in these complexes and ligands are coordinated to the metal centre in a bidentate (S/ Se, N) mode. The molecular complexes 1 and 2 have been explored as potential catalysts in O À arylation reaction between substituted aryl halides and phenol. Both the complexes showed excellent efficiency towards this coupling and a TON of 990 (maximum TOF 310) has been achieved using 0.1 mol% of catalyst 2. The effect of the nature of chalcogen donor atom (S/Se) on catalytic efficiency of the complexes has been observed as selenium congener was more efficient than sulphur counterpart.

Catalytically active nanosized Pd9Te4(telluropalladinite) and PdTe (kotulskite) alloys: first precursor-architecture controlled synthesis using palladium complexes of organotellurium compounds as single source precursors

“…This Pd–Cl bond length in the 1 is consistent with the literature reports. 34 The Pd–Te bond length in both the complexes are similar i.e. 2.5057(6) and 2.5002(4) Å in complexes 1 and 2 respectively.…”

Molecular Organosulphur, Organoselenium and Organotellurium Complexes as Homogeneous Transition Metal Catalytic Systems for Suzuki Coupling

“…Geometry around the metal is also affected by the ligands. The lability of the metal‐donor bond is also a crucial characteristic of metal complexes [88] . The electronic and steric properties of the ligand influence the catalytic features of the metal [112] .…”

“…These ligands have been used in the development of homogeneous catalytic systems [18–102] . All such ligands behave as Lewis bases due to the presence of chalcogen (S/Se/Te) donor sites, and form a coordinate (i. e. dative) bond with the metal through such sites.…”

“…Moisture‐insensitivity is an extra advantage. In addition to Suzuki coupling, they show catalytic potential for several other chemical transformations [10,11,87–107] too. In the recent past, some of such systems have also been used for its green catalysis in water and room temperature [20,21,27,33,34,44,48,49,50,55,61,63,66,73,74] .…”

Functionalization of graphene oxide with a hybrid P, N ligand for immobilizing and stabilizing economical and non-toxic nanosized CuO: an efficient, robust and reusable catalyst for the C–O coupling reaction inO-arylation of phenol

“…This method requires harsh reaction conditions such as a high temperature (>200 °C), excessive use of phenol, a long reaction time and use of a stoichiometric amount of copper. 59,60 To overcome these limitations, a variety of homogeneous, 61–64 heterogeneous and nanocatalytic 1–7 (nanoparticles of Pd, Cu, CuO, CuI, Ni, and Fe) systems have been developed. Among such systems, the use of noble transition metal (such as palladium) based catalysts is avoided in large scale or industrial applications due to their high cost and toxicity.…”