N-Heterocyclic-Carbene Complexes Readily Prepared from Di-μ-hydroxopalladacycles Catalyze the Suzuki Arylation of 9-Bromophenanthrene

Abstract

New cyclometalated palladium complexes of general formula [Pd(Bmim)(X)(C∧N)] have been synthesized by a novel reaction route involving di-μ-hydroxo-palladacycles [{Pd(μ-OH)(C∧N)}2] (C∧N = 2-benzoylpyridine (Bzpy), I, previously unreported, or C∧N = 2-phenylpyridine (Phpy), II)] and 1,3-butylmethyl­imidazolium salts [HBmim]X (X: Cl, Br, I, or saccharinate (Sacc); a, b, c, or d complexes, respectively). This simple acid–base reaction could not be achieved under identical conditions when corresponding di-μ-acetate complexes were used as starting materials. An alternative pathway to NHC/imidate complexes has also been explored by reacting IIb with [Ag(Phthal)(SMe2)]2 (Phthal = phthalimidate, e) to obtain [Pd(Bmim)(Phthal)(Phpy)], IIe. Structural characterization by X-ray diffraction of complexes Id, IIb, IId, and IIe has confirmed the proposed formulas. The mononuclear complexes have shown to catalyze the scalable Suzuki–Miyaura cross-coupling of 9-bromophenanthrene with a wide scope of aryl boronic acids, irrespective of their electronic properties and at a very low catalyst concentration of 0.01%.

Structure controlled Au@Pd NPs/rGO as robust heterogeneous catalyst for Suzuki coupling in biowaste‐derived water extract of pomegranate ash

“…The Suzuki coupling of 9‐bromoanthracene provides low yields of coupling products in several reports. [ 58–60 ] Negligible influence of the nature and positions of functional groups was noticed in WEPA mediated Suzuki coupling of Au@Pd NPs/rGO. Ortho substituted aryl bromides such as 9‐bromophenanthrene, 2‐bromoanisole, 2‐bromotoluene, and 2‐nitrobromobenzene are observed to form high yield of Suzuki coupling products under present conditions (Table 2, products 3t , 3u , 3z , 3aa , and 3ab ).…”

Synthesis, characterization and catalytic activity in Suzuki–Miyaura coupling of palladacycle complexes with n‐butyl‐substituted N‐heterocyclic carbene ligands

“…In this study, two methods were used for the synthesis of palladacyclic complexes. Firstly, an acetate‐bridged palladacyclic dimer was obtained successfully by cyclopalladation of 2‐phenylpyridine according to a published procedure and subsequently three NHC palladacycles 4a – c were prepared from the reactions of this dimer and the corresponding imidazolium salts . From the 13 C NMR spectra, the diagnostic Pd–N C N resonances appeared as a singlet between 171.9 and 172.3 ppm.…”

Cross coupling reactions catalyzed by (NHC)Pd(II) complexes

“…109 The cyclometalated complex C76 was shown to catalyze the coupling of 9-bromophenanthrene with a wide scope of aryl boronic acids, irrespective of their electronic properties and at a very low catalyst concentration (Table 8, entries 37-39). 110 Commercially available Pd-NHC complex (C77) acts as precatalyst under very mild conditions using a mixture of ethanol/water as solvent at low catalyst loading (Table 8, entries 40-43). 111 Stereospecific and regioselective cross coupling of 2-arylaziridines with arylboronic acids by [(SIPr)Pd(cinnamyl)Cl], C77, was very recently described to obtain configurationally defined arylphenethylamine derivatives.…”

“…110 Commercially available Pd-NHC complex (C77) acts as precatalyst under very mild conditions using a mixture of ethanol/water as solvent at low catalyst loading ( C77, was very recently described to obtain configurationally defined arylphenethylamine derivatives.…”