Ruthenium Complexes of κ(P)- and κ(P)-η⁶-Coordinated KITPHOS Monophosphines: Efficient Catalysts for the Direct Ortho Arylation of 2-Phenylpyridine andN-Phenylpyrazole with Aryl Chlorides

Abstract

Thermolysis of the P-coordinated KITPHOS monophosphine complex [(p-cymene)RuCl2(KITPHOS)] in chlorobenzene at 120 °C resulted in displacement of the p-cymene to afford [{κ(P)-η6-KITPHOS}RuCl2], the first example of a constrained-geometry complex in which the κ(P)-bonded diphenylphosphino group and the η6-coordinated proximal phenyl ring are connected by an unsaturated two-carbon tether; both complexes form efficient catalysts for the direct ortho arylation of 2-phenylpyridine and N-phenylpyrazole with a range of aryl chlorides.

Facile Arene Ligand Exchange in p-Cymene Ruthenium(II) Complexes of Tertiary P-Chiral Ferrocenyl Phosphines

“…Here, phosphines with pendant aromatic groups in close proximity to the phosphorus atom are predominantly used as polydentate ligands for the formation of tethered ruthenium complexes. 18−26 Utilizing the chelate effect to stabilize the arene–metal interaction is one major benefit of tethered complexes compared to nontethered complexes. 21,27 In the case of chiral ligands, another advantage is a restrained stereochemical situation which raises the racemization barrier of the chiral tethered complex.…”

C–H Bond Activation for Arylations

“…In 2011, Doherty et al [25] reported the application of [{κ(P)-6 -KITPHOS}RuCl 2 ] (KIT-PHOS = 11-Dicyclohexylphosphino-12-phenyl-9,10-ethenoanthracene, and in fact this was obtained by thermolysis of the P-coordinated KITPHOS monophosphane complex [(pcymene)RuCl 2 (KITPHOS)] in chlorobenzene at 120 ∘ C) for the selective mono-ortho-arylation of 2-phenylpyridine and N-phenylpyrazole. The reaction conditions entailed heating the 2-phenylpyridine and N-phenylpyrazole with a variety of aryl chlorides in the presence of 2.5 mol% of the catalyst at 120 ∘ C in NMP for 24 h. The selected reaction afforded the monoarylated product, but some diarylated product was also obtained.…”

Recent Advances in C–H Bond Functionalization with Ruthenium-Based Catalysts

“…Doherty et al achieved the selective monoarylation of 2-phenylpyridine and phenylpyrazoles using ruthenium(II) catalysts, [RuCl 2 (p-cymene)(PPh 2 L)], which gave predominantly monoarylated products with a minor or insignificant amount of diarylated products (Scheme 9) [55]. The reaction gave 76% of monoarylation and 9% diarylation with chlorobenzene as the arylating agent.…”