Chiral Ferrocenyl-Bismuthines containing N/O donor pendant arm: Syntheses and molecular structures

Abstract

Some new chiral substituted ferrocenyl bismuthines CpFe(2-[Me2NCH(R)]C5H3)BiPhCl where R = H (1) or Me (2) and CpFe(2-[Me2NCH(R)]C5H3)BiPh2 where R = H (3) or Me (4) (Cp = cyclopentadienyl) containing a Rac-2-[(Me2NCH(R)] pendant arm on the ferrocenyl ring were synthesized. Nucleophilic substitution reaction of mono ammonium salt Rac-{[CpFe{2-(Me3N+CH2)C5H3}BiPh2][I−] (5) by o-hydroxyacetaphenone, salicyladehyde, N-methylpiperazine and 4′- aminobenzo-15-crown-5 in acetonitrile gave new ferrocenyl bismuthines [CpFe{2-(RCH2)C5H3}BiPh2] where R = OC6H4-2-C(O)Me (6), OC6H4-2-C(O)H (7), N(CH2CH2)2NMe (8) and NHC6H4-3,4-O-cyclo{(CH2)2-O}4 (9) respectively with N or O containing pendant arm. All the new compounds were characterized by 1H NMR, 13C NMR, FAB+, and High-Resolution Mass Spectrometry. All the compounds presented in this work present planar chirality because of 1,2-disubstituted ferrocene. In the solid-state, the presence of the ferrocenyl group influences the stereoelectronic properties in the molecule and Bi···N or Bi···O hypervalent interaction could not be observed in compounds with BiPh2 fragment while this interaction was observed in compounds with BiPhCl fragment. For compounds (1)-(4), (6)-(8) and (10), NMR spectra obtained at different temperatures show the association and/or dissociation of hypervalent N···Bi coordination in these compounds. Molecular structures of compounds (1), (2) and (10) show distorted pseudo-trigonal bipyramidal geometry (see-saw structure) at bismuth center with intramolecular Bi···N hypervalent interaction while (6) and (7) present a distorted pseudo-trigonal pyramidal geometry and do not show hypervalent Bi···O interaction. Crystal structures of these compounds show that CFc-Bi bond length is shorter than CPh-Bi bond length due to lower group electronegativity of ferrocenyl vs phenyl and bidentate nature of FcN ligand in ferrocenyl bismuthines.