SciPROP-R: An Effective Bisphosphine Ligand for the Chemo-selective Iron-Catalyzed Suzuki–Miyaura Coupling of Alkyl Chlorides

Abstract

Novel 2-substituted 1,3-bis[bis(3’,5’-di-tert-butyl phenyl)phosphino]propanes (SciPROP-R; 1-R), as well as their iron complexes FeCl2(SciPROP-R) 2-R, are synthesized. Single-crystal X-ray analysis and solution-phase Fe K- and L-edge XAS of 2-R reveals that these complexes maintain tetrahedral geometry and hence of paramagnetic high-spin properties both in the solid state and in the solution phase. 31P NMR results demonstrate that the superior coordination ability of SciPROP-TB (1-TB) is due to the bulky tert-butyl group at position 2 of the propane-1,3-diyl linker of the ligand. These novel iron-complexes catalyze Suzuki–Miyaura-type cross coupling under mild conditions. Notably, Iron(II) chloride–1-TB complex (2-TB) exhibits excellent catalytic activity owing to the high coordination ability and electron-donating nature of 1-TB, being effective for chemoselective cross coupling between various alkyl chlorides and arylboron compounds. A series of 2-R-substituted 1,3-bis[bis(3’,5’-di-tert-butyl phenyl)phosphino]propane SciPROP-R are designed and synthesized. Their iron complexes, especially FeCl2(SciPROP-TB), are effective catalysts for the highly chemoselective iron-catalyzed Suzuki–Miyaura-type cross-coupling reaction of alkyl chlorides with arylboron compounds.