Synthesis and structure of ferrocenylphosphinic acids

• We synthesized ferrocenylphosphinic acids as ligands for coordination polymers.
• Spontaneous racemization takes place for monosubstituted ferrocenylphosphinic acids.
• Difference of hydrogen bonding was observed for ferrocene-1,1′-diyl-bisphosphinic acids.
• Conformation of ferrocenephosphinic acids depend on substituent's at phosphorus atoms.

The series of ferrocenylphosphinic acids Fc(P(R)(O)(OH)) (1a–d) and ferrocene-1,1′-diyl-phosphinic acids Fc(P(R)(O)(OH))2 (2a–d) (R = H (a), Me (b), Et (c), Ph (d)) have been obtained and studied using X-ray single crystal diffraction, IR-spectroscopy and quantum chemistry. The intermolecular hydrogen bonding in 1a–d proceeds highly stereoselectively and results in formation of racemic conglomerate of 1d. The formation of inter- and intra-molecular hydrogen bonds for disubstituted acids 2c–d depends on substituent at phosphorus atoms.

The intermolecular hydrogen bonding in mono-substituted ferrocenylphosphinic acid Fc(P(R)(O)(OH)) (R = H, Me, Et, Ph) proceeds highly stereoselectively with formation of enantiomorphous chains. In disubstituted acids 1,1′-Fc(P(R)(O)(OH))2 (R = Me, Et, Ph) molecular and crystal structure is determined by the competition of intermolecular and intramolecular hydrogen bonding.Figure optionsDownload as PowerPoint slide