1,1′-Bis(oxazolin-2-yl)ferrocenes: An investigation of their complexation behavior toward [Pd(η3-allyl)Cl]2

Article abstract of DOI:10.1002/ejic.200400737

The coordination behavior of several aryl- and alkyl-bis(oxazolinyl) ferrocenes, which were prepared in high yields from ferrocene-1,1′- dicarbonyl dichloride and enantiomerically pure or racemic amino alcohols via the corresponding bis(β-hydroxyamide)s and dimesylates or ditosylates as intermediates, toward [Pd(η³-allyl)Cl]₂ was investigated by ESI mass spectrometry. The synthesized compounds were characterized by NMR spectroscopy and elemental analysis and the molecular structures of 1,1′-bis[(R)-4-isopropyloxazolin-2-yl]-ferrocene (6b), 1,1′-bis[(S)-4-isopropyloxazolin-2-yl]ferrocene (7b), 1,1′-bis[(S)- 4-sec-butyloxazolin-2-yl]ferrocene (11b), 1,1′-bis[(S)-4-tert- butyloxazolin-2-yl]ferrocene (12b), 1,1′-bis[(R)-4-phenyloxazolin-2-yl] ferrocene (13b), and 1,1′-bis[(S)-4-phenyloxazolin-2-yl]ferrocene (14b) were determined by single-crystal X-ray diffraction analysis. The coordination behavior studies by ESI-MS show a strong preference for monodentate complex formation. This result is supported by theoretical studies carried out at the B3LYP level of theory. It was found that the latter coordination type of 1,1′-bis[(S)-4-methyloxazolin-2-yl]ferrocene (1b) to an allylpalladium moiety is kinetically favored over the bidentate one.