Synthesis, characterization, photophysical properties, and catalytic activity of an SCS bis(N-heterocyclic thione) (SCS-NHT) Pd pincer complex

Abstract

Treatment of 1,3-bis(3'-butylimidazolyl-1'-yl)benzene diiodide with elemental sulfur in the presence of a base produced a bis(N-heterocyclic thione) (NHT) pincer ligand precursor. Its reaction with PdCl2(CH3CN)2 produced chloro[1,3-bis(3'-butylimidazole-2'-thione-κ-S)benzene-κ-C]palladium(ii), a 6,6-fused ring SCS-NHT palladium pincer complex. This air stable compound is, to our knowledge, the first SCS pincer complex that utilizes N-heterocyclic thione (NHT) donor groups. The molecular structures of the ligand precursor and the palladium complex were determined by X-ray crystallography and computational studies provided insight into the interconversion between its rac and meso conformations. The photophysical properties of the complex were established, and its catalytic activity in Suzuki, Heck, and Sonogashira cross-coupling reactions was evaluated.

Thiourea-Derived Chelating Ligands and Their Organometallic Compounds: Investigations into Their Anticancer Activity

“…The imidazolium-based NHC precursors can also be converted into thiourea derivatives [ 26 ], featuring a soft S-donor for metal coordination. Such thiones are good σ-donors and weak π-acceptors and a wide range of metal complexes have been synthesized, often for investigations into their catalytic properties [ 26 , 27 , 28 , 29 , 30 , 31 ]. As with thiones [ 32 , 33 , 34 , 35 ], some of their metal complexes have shown biological activity.…”

Symmetrical and Non‐symmetrical Pd (II) Pincer Complexes Bearing Mesoionic N‐heterocyclic Thiones: Synthesis, Characterizations and Catalytic Properties

“…have reported a series of bis (imidazolin‐2‐thione) analogues Btb (Table 1), [ 21 ] and a syn orientation was reported for n Bu‐ Btb . [ 21a ] The calculated C‐S bond distances up to 1.6975 Å is close to the typical C‐S partial double bond distance (1.72 Å), [ 22 ] and thus the thiocarbonyl moieties of 3a / 3b are better described as partial double bonds. In addition, the C‐S bond lengths of 3a / 3b are slightly longer than those for n Bu‐ Btb indicating a less pronounced C‐S double bond character in the former case.…”

“…have reported the cyclopalladations of Btb (Scheme 5), in which cases NaOAc was not utilized. [ 21 ] As such, 3a was used as a representative, and under Hollis's condition, the metalation reactivity in the absence of NaOAc was examined. 1 H NMR spectrum of the as‐formed product shows a very downfield singlet at 12.17 ppm, which is tentatively assigned to the C aryl ‐H a proton of non‐cyclopalladated complex 7a .…”

Sonogashira Coupling (Cu/Amine‐Free) of ArBr/Cl in Aerobic Condition and N‐Benzylation of Aniline with Benzyl Alcohol Catalyzed by Complexes of Pd(II) with Sulfated/Selenated NHCs

“…The reported catalysts and conditions for optimum performance are as follows. The important reaction conditions for each species follow it in parentheses: benzimidazole based Pd(II) NHC complex (1 mol%, 100 °C), palladium‐1,3,5‐triaza‐7‐phosphaadamantane complex (1‐2.5 mol%, 24 h), Pd(II) complexes of bis‐NHC based (C, N, C) pincers (1 mol%, 140 °C, 4 h), and palladium complex of (S, C, S) pincer (2 mol%, CuI, 18 h) . Thus performance of 1–4 is better relative to these reported systems.…”