Palladium(II) Complexes of Homologated Ferrocene Phosphanylether and Thioether Ligands

Article abstract of DOI:10.1002/ejic.201701057

The reaction of [1′-(diphenylphosphanyl)ferrocenyl]methanol/borane (1:1) with in situ formed N,N,N′,N′,S-pentamethylisothiouronium iodide and sodium hydride, followed by removal of the borane protecting group with 1,4-diazabicyclo[2.2.2]octane, afforded 1-(diphenylphosphanyl)-1′-[(methylthio)methyl]ferrocene (3) as a new, homologated, hybrid phosphanylferrocene ligand. Compound 3 and the congeneric phosphanyl ether 2 were studied as ligands in Pd^II complexes. When treated with [PdCl₂(MeCN)₂] in a Pd/ligand ratio of 1:1, compound 3 furnished a mixture of two Pd complexes, including the ligand-bridged dimer [{μ(P,S)-3}PdCl₂]₂ (6), which was structurally characterized. Upon increasing the amount of ligand to 2 equiv., a similar reaction produced the bis(phosphane) complex [PdCl₂(3-κP)₂] (7). Bridge-cleavage reactions of the dipalladium complex [(L^NC)Pd(μ-Cl)]₂ {L^NC = 2-[(dimethylamino-κN)methyl]phenyl-κC¹} with donors 3 and 2 proceeded in a uniform manner to give the corresponding phosphane complexes [(L^NC)PdCl(3-κP)] (8) and [(L^NC)PdCl(2-κP)] (9). Conversely, removing the Pd-bonded chloride from these complexes with AgClO₄ generated the bis(chelate) complex [(L^NC)Pd(3-κ²P,S)] (10) and the aqua complex [(L^NC)Pd(H₂O)(2-κP)] (11), respectively, both of which could be converted back into their precursors by adding Bu₄NCl. The structures of the complexes 6–11 (some in solvated form) were determined by single-crystal X-ray diffraction analysis.