Synthesis and structural characterization of phosphinoferrocene carboxylic acids with extended carboxyl pendants and their palladium(II) phosphinocarboxylate complexes

Abstract

Two phosphinoferrocene carboxylic acids differing in the two-carbon spacer separating the phosphinoferrocene moiety and the carboxyl group, Ph2PfcCH=CHCO2H (1a) and Ph2PfcCH2CH2CO2H (1b; fc = ferrocene-1,1′-diyl), were prepared from aldehyde Ph2PfcCHO by Horner-Wadsworth-Emmons olefination, reduction and hydrolysis. These acids reacted with [(LNC)Pd(acac)] (LNC = 2-[(dimethylamino-κN)methyl]phenyl-κC1, acac = pentane-2,5-dionate) under protonation and elimination of the Pd-bound acetylacetonate ligand to afford the respective phosphinocarboxylate complexes, namely, the P,O-bridged dimer [(LNC)Pd{μ(P,O)-Ph2PfcCH=CHCO2}]2 (6a) and the coordination polymer [(LNC)Pd{μ(P,O)-Ph2PfcCH2CH2CO2}]n (6a). The crystal structures of P-sulfides prepared from acids 1a and 1b, compounds Ph2P(S)fcCH=CH2CO2H and Ph2P(S)fcCH2CH2CO2H, and the phosphinocarboxylate complexes 6a and 6b (in solvated form) were determined by single-crystal X-ray diffraction analysis.