Palladium(II) Complexes with 1,1‘−Bis(diphenylphosphino)ferrocenes [Fe(η⁵-C₅R₄PPh₂)₂]n⁺(dppf, R = H,n= 0; dppomf, R = Me,n= 0; dppomf⁺, R = Me,n= 1). Synthesis, Characterization, and Catalytic Activity in Ethene Methoxycarbonylation

Several palladium(II) complexes with 1,1‘-bis(diphenylphosphino)octamethylferrocene (dppomf) and its oxidized form 1,1‘-bis(diphenylphosphino)octamethylferrocenium (dppomf + ) have been synthesized and characterized by spectroscopic and electrochemical methods. For comparative purposes, analogous Pd(II) derivatives with 1,1‘-bis(diphenylphosphino)ferrocene (dppf) have been also prepared. Single-crystal X-ray analyses have been carried out for the square-planar mononuclear compounds [Pd(H 2 O) 2 (dppf)](OTf) 2 and [Pd(H 2 O) 2 (dppomf)](OTf) 2 and for the binuclear complex [Pd(μ-OPF 2 O)(dppomf + )] 2 (BF 4 ) 4 ·6CH 2 Cl 2 in which two [Pd(dppomf + )] 3+ moieties are held together by the oxygen atoms of two bridging PO 2 F 2 - groups derived from the oxidative degradation of PF 6 - ions. Selected dppf and dppomf Pd(II) complexes have been employed as catalyst precursors for the methoxycarbonylation of ethene (600 psi, 1:1 CO/C 2 H 4, 85 °C). It has been found that dppomf generates selective catalysts for the production of methyl propanoate, while dppf leads to a variety of low-molecular-weight oxygenates spanning from methyl propanoate to alternating oligoketones.