Synthesis, Characterization Of Two Chiral Tertiary Ferrocenylamines And Their Cyclopalladations

Condensation of (R) or (S)-α-methylbenzylamines and acetylferrocene catalyzed by titanium chloride in dry ether at room temperature resulted in ferrocenylaldimines (RC)-[(η⁵-C₅H₅)Fe(η⁵-C₅H₄CCH₃=NCHCH₃C₆H₅)] and (SC)-[(η⁵-C₅H₅)Fe(η⁵-C₅H4- CCH3=NCHCH₃C₆H₅)] , respectively in moderate yields. Reduction of these imines with sodium borohydride in methanol produced quantitative secondary ferrocenylamines (RC6, RC8)-[(η⁵-C₅H₅)Fe(η⁵-C₅H₄CHCH₃NHCHCH₃C₆H₅)] and (SC6, SC8)-[(η⁵-C₅H₅)Fe(η⁵-C₅H₄CHCH₃NHCHCH₃C₆H₅)] . Reductive methylation of these secondary ferrocenylamines with sodium cyanoborohydride, formaldehyde in aceto-nitrile and acetic acid gave out the corresponding tertiary ferrocenylamines (RC6,RC8)-[(η⁵-C₅H₅)Fe(η⁵-C₅H₄CHCH₃NCH₃CHCH₃C₆H₅)] and (SC6, SC8)-[(η⁵-C₅H₅) Fe(η⁵-C₅H₄CHCH₃NCH₃CHCH₃C₆H₅)] . Cyclopalladation of these tertiary ferrocenylamines with sodium tetrachloropalladate in methanol and dichloromethane led to cyclopalladated complexes {(RC6, SN, RC8, RP) -σ-Pd[(η⁵-C₅H₅)Fe(η⁵-C₅H₃CH CH₃NCH₃CHCH₃C₆H₅)] Cl(PPh3)} and {(SC6, RN, SC8)-σ-Pd[(η⁵-C₅H₅)Fe(η⁵-C₅H4 CHCH₃NCH₃CHCH₃C₆H₄)] Cl(PPh3)}. The sec- and tert-ferrocenylamines as well as their cyclopalladated complexes were characterized by elemental analysis, IR and 1HNMR. The structures of two cyclopalladated complexes were confirmed by X-Ray single crystal diffraction, and the possible mechanism for the formation of cyclopalladated complexes was discussed.