Mercaptoaryl‐Oxazoline Complexes of Palladium and Their High Activities as Catalysts for Suzuki–Miyaura Coupling Reactions in Water

Abstract

The synthesis, spectroscopic characterization, and catalytic activities of a series of PdII complexes bearing the monoanionic, bidentate ligand 2‐(2‐thiophenyl)‐4,4‐dimethyloxazoline (S‐Phoz) are reported. These complexes were used as precatalysts for Suzuki–Miyaura coupling reactions under aqueous conditions. The dimers [{PdX(S‐Phoz)}2] (X = Cl, Br, I; 1–3) were treated with the N‐heterocyclic carbene (NHC) ligand 1,3‐bis(2,4,6‐trimethylphenyl)imidazol‐2‐ylidene (IMes) to afford the mononuclear complexes [PdX(S‐Phoz)(IMes)] (X = Cl, Br, I; 4–6). The σ‐donor/π‐acceptor complexes [PdCl(S‐Phoz)(EPh3)] (E = P, As, Sb; 7–9) were synthesized to evaluate the influence of a second donor ligand on the catalytic activity. Within the [PdCl(S‐Phoz)L] series, the activity trend for L follows the trend PPh3 > IMes ≈ AsPh3 > SbPh3. The sulfur‐bridged dinuclear complexes 1–3 are highly active for the benchmark coupling of p‐bromoacetophenone with phenylboronic acid and exhibit turnover frequencies (TOFs) of up to 16000 h–1. DFT and G0W0 calculations were performed to rationalize the facile reduction and, hence, excellent activities of the dinuclear complexes.

Rational Design of Sterically Hindered and Unsymmetrical NpyNimOph Pincer‐Type Ligands and Their Palladium(II) Complexes: Catalytic Applications in Suzuki–Miyaura Reaction and Allylation of Aldehydes

“…The mechanism for the SMC reaction involving other aryl halide and arylboronic acids is very similar to the one depicted in Scheme . DFT calculations were performed to gain insight into the mechanism and driving force for the formation of cross‐coupling product . For complexes 1 and 3 shown in Figure and for complexes 2 and 4 ESI Fig S90.…”

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

“…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.…”

“…Thereafter, a large number of catalysts have been designed using such ligands as the building blocks to carry out the phosphine‐free catalysis of several chemical transformations. At present, organosulphur ligands constitute the sub‐class that is the most widely explored among all the organochalcogen ligands [12,18–67] . Their synthesis is straight‐forward and manipulations do not require inert atmosphere in majority of the cases.…”

Synthesis and structure of two isomers of a molybdenum(II) 2-butyne complex stabilized by bioinspired S,N-bidentate ligands

“…Thereafter, the reversible binding of C 2 Me 2 and C 2 Ph 2 (Peschel et al, 2019) was investigated, with a particular focus on the flexibility of the S-Phoz ligand. The latter has also found application in Ni, Pd and Pt compounds (Peschel et al, 2015b;Holzer et al, 2018), as well as in Zn (Mugesh et al, 1999) and Fe (Bottini et al, 2010) complexes.…”