Solid-phase cyclopalladation in S,C,S′-pincer systems: rising alternative for synthesis in solution

Abstract

In pursuit of a new and simple approach to complex organometallic systems, the possibility of formation of a palladium-carbon bond in the solid state via direct cyclopalladation has been studied toward several S,C,S'-pincer ligands with thione sulfur donors of different nature. It is found that mixtures of the ligand and PdCl2(NCPh)2 obtained by the manual grinding of reactants in a mortar efficiently undergo solid-phase cyclometalation upon heating in open test tubes without the addition of a solvent to afford the desired pincer-type products in high yields. In the case of the most active bis(thiocarbamoyl) ligand, solid-phase cyclopalladation proceeds even at room temperature. For the challenging bis(thiophosphoryl) derivative, the preformed non-metallated complexes can be successfully used as a starting material to essentially enhance the yield of the desired pincer complex compared to the conventional synthesis in solution. The solid-phase transformation is followed by IR spectroscopy and SEM analysis. The results obtained show that the suggested solid-phase methodology can serve as a powerful alternative to conventional synthesis of pincer complexes in solution.

Design of pincer complexes based on (methylsulfanyl)acetic/propionic acid amides with ancillary S‐ and N‐donors as potential catalysts and cytotoxic agents

“…Recently we have shown that simple heating of homogenized mixtures of a pincer‐type ligand and appropriate Pd(II) precursor, obtained by grinding of the reactants in a mortar, can become a powerful alternative to conventional synthesis of complex organometallic systems in solution . The suggested solid‐phase methodology appeared to be efficient for production of several series of C‐metallated pincer complexes combining thiophosphoryl donor groups with ancillary benzothiazole (compounds XVII – XIX ; Scheme ),[10b] thioamide (compounds XX , XXI ) and thiophosphorylamino ( XXII ) moieties [10a]. In the case of the highly reactive hybrid bis(thioamide) derivative, the formation of pincer complex XXIII was observed even at room temperature [10a].…”

“…The suggested solid‐phase methodology appeared to be efficient for production of several series of C‐metallated pincer complexes combining thiophosphoryl donor groups with ancillary benzothiazole (compounds XVII – XIX ; Scheme ),[10b] thioamide (compounds XX , XXI ) and thiophosphorylamino ( XXII ) moieties [10a]. In the case of the highly reactive hybrid bis(thioamide) derivative, the formation of pincer complex XXIII was observed even at room temperature [10a]. Not long ago the synthesis of an organometallic Pd(II) pincer complex XXIV was accomplished for the first time via CH bond activation of a bis(thiocarbamate) ligand with PdCl 2 (NCPh) 2 under mechanochemical conditions both by grinding of the reactants in a mortar and in a vibration ball mill at gram scale .…”

Pincer Complexes with Thione Sulfur Donors

“…These reactions appeared to be the first examples of solid-phase synthesis of pincer complexes. Recently, the solid-phase strategy has been successfully used for synthesis of S,C,S 0 -pincer systems with different thione sulfur donors [99].…”

Synthesis, Photophysical Properties and Catalytic Activity of Ƙ3-SCS Pincer Palladium (II) Complex of N,N'-Di-Tert-Butylbenzene-1,3-Dicarbothioamide Supported by DFT Analysis

“…Extensive studies have been carried out on several pincer ligands with various combinations of C, N, S and P donors and related palladium/platinum complexes have been investigated for their photophysical and catalytic properties [7][8][9][10][11][12]. Amongst the well-known pincer complexes, the thioamide based ligands with SCS type are relatively less explored compared to the others [13,14]. Therefore, in order to examine the binding properties and associated photophysical and catalytic properties of these complexes, one of the methyl groups of each side of N,N,N',N'-tertamethylbenzene 1,3-dicarbothioamide are replaced by bulky tert-butyl group and another by hydrogen atom and employed for the complexation with Pd(II).…”