Low‐Valent Nickel and Palladium Complexes with 1,1′‐Bis(phosphanyl)ferrocenes: Syntheses and Structures of Acrylic Acid and Ethylene Complexes

Abstract

AbstractThermally stable acrylic acid complexes with low‐valent nickel or palladium of the type [(L)M(η2‐CH2=CH‐COOH)] [1a: M = Ni, L = 1,1′‐bis(diphenylphosphanyl)ferrocene (dppf), 1b: M = Ni, L = 1,1′‐bis(diisopropylphosphanyl)ferrocene (dippf), 1c: M = Pd, L = dippf] were obtained by reaction of [Ni(cod)2] or [(L)Pd(nb)] with acrylic acid in the presence of the phosphane ligands. X‐ray diffraction analysis of 1a and 1c, respectively display that only the olefin part is coordinated. Hydrogen bonds between two carboxyl groups result in dimers in the solid state. The isomeric nickela‐cyclic carboxylates of the type [(L)Ni(CH2CH2COO)] are stable complexes in case of 2a (L = dppf) and 2b (L = dippf) whereas the unstable compound 2c [L = 1,1′‐bis(di‐tert‐butylphosphanyl)ferrocene (dtbpf)] undergoes fast reductive decoupling to form CO2 and the ethylene complex [(dtbpf)Ni(ethylene)] (3c). The related complex [(dippf)Ni(ethylene)] (3b) was prepared from nickel(0) complexes by ligand exchange reaction. 3b and 3c were characterized by elemental analyses, NMR spectroscopy and X‐ray structure analysis of single crystals.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)