Revisiting Claims of the Iron‑, Cobalt‑, Nickel‑, and Copper-Catalyzed Suzuki Biaryl Cross-Coupling of Aryl Halides with Aryl Boronic Acids

• Published in: Organometallics Vol. 38; no. 8; pp. 1770 - 1777
• Main Authors: Tailor, Sanita B, Manzotti, Mattia, Asghar, Soneela, Rowsell, Benjamin J. S, Luckham, Stephen L. J, Sparkes, Hazel A, Bedford, Robin B
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 22.04.2019; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Physical Sciences; Science & Technology; ARYLBORONATE ESTERS; PALLADIUM; IODIDES; LIGANDS; CHLOROARENES; TRANSMETALATION; COMPLEXES; ALKYL-HALIDES
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/acs.organomet.9b00083

Intrigued by recent reports on the surprisingly excellent activity of a range of cobalt-, iron-, copper-, and nickel-based catalysts in the Suzuki biaryl cross-coupling of simple aryl boronic acids with aryl halides, we undertook a reexamination of the syntheses of representative examples of the reported precatalysts and their application to the catalytic reaction. A reported PNP−Fe pincer complex proved to be a mixture of starting materials; a mono-Schiff base cobalt complex in fact the bis-ligated adduct and a monomeric copper­(II) PNP–pincer complex a di- or oligomeric copper­(I) species. In our hands, neither these complexes nor any other of the selected precatalysts investigated showed any activity in a Suzuki cross-coupling reaction of an electronically activated aryl bromide with phenyl boronic acid. Meanwhile, switching the nucleophile to the BuLi-activated phenyl boronic pinacol ester gave some promising activity with cobalt precatalysts.