Synthesis and application of novel ionic phosphine ligands with a cobaltocenium backbone

Six novel ionic phosphine ligands with a cobaltocenium backbone, 1,1′-bis(dicyclohexylphosphino) cobaltocenium hexafluorophosphate () (1a), 1,1′-bis(di-iso-propylphosphino) cobaltocenium hexafluorophosphate () (2a), 1,1′-bis(di-tert-butylphosphino) cobaltocenium hexafluorophosphate () (3a), and the monophosphine ligand (Cc⁺ = cobaltocenium; R = Cy, 1b; R = i-Pr, 2b; R = t-Bu, 3b) were synthesized and characterized by elemental analysis, spectroscopy, and X-ray diffraction techniques. These ligands are air-stable and useful for Suzuki coupling reactions in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (), enabling high catalytic activity.