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(H2O)2(dppf)](OTf)2 and [Pd(H2O)2(dppomf)](OTf)2 and for the binuclear complex [Pd(μ-OPF2O)(dppomf+)]2(BF4)4·6CH2Cl2 in which two [Pd(dppomf+)]3+ moieties are held together by the oxygen atoms of two bridging PO2F2 - groups derived from the oxidative degradation of PF6 - ions. Selected dppf and dppomf Pd(II) complexes have been employed as catalyst precursors for the methoxycarbonylation of ethene (600 psi, 1:1 CO/C2H4, 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.

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A family of bimetallic complexes [Cp(CO)2FeCCArCCFe(CO)2Cp] {Cp= C5H5; 6a-g, Ar= C4H2S (a); 3-(C4H9)-C4HS (b); 3-(C16H33)-C4HS (c); C6H4 (d); 2,5-bis(OC4H9)-C6H2 (e); 2,5-bis(OC8H17)-C6H2 (f); (C6H4)2 (g)} was prepared by the three-step Pd-catalysed Extended-One-Pot (EOP) synthetic protocol from Bu3SnCCH, XArX (X=I,Br) and Cp(CO)2FeI. Complexes 6a,d,g were then exposed to ultraviolet irradiation in presence of an equivalent amount of 1,2-bis(diphenylphosphyne)ethane (dppe) to form the corresponding bimetallic complexes [Cp(dppe)FeCCArCCFe(dppe)Cp] (7a,d,g). Compounds 6a-g and 7a,d,g were characterised by Ciclic Voltammetry (CV). The most significant electrochemical information comes from the oxidation of the dppe derivatives. The E° separations between the subsequent reversible waves suggest that the efficiency of the metal-metal electronic coupling decreases in the order 6a > 6d > 6g. Complexes 7a and 7g were also chemically oxidised with [Fe(Cp*)]2[BF4] {Cp*= C5(CH3)5} and [Fe(Cp)]2[BF4] respectively, and the Near Infrared (NIR) spectra of the mixed valence species 7a+ and 7g+ were recorded. A strong Charge Transfer band (ICT) was observed only for the radical cation 7a+. While this finding confirms the existence of electronic interaction between the two termini when a 2,5-thiophene group is present in the spacer, the NIR spectrum of 7g+ reveals a reduced efficiency in conveying electrons when the C4H2S moiety is replaced by a 4,4'-biphenyl. In order to rationalise and quantify the extent of electronic communication, ruled by geometrical and electronic factors, Density Functional computational results on selected [Cp (PH3)2Fe and [Cp(CO)2Fe binuclear model complexes are reported