Cyclopalladation of N-phenyl-4-ferrocenylmethylpyrazoles: Crystal structure of [Pd{κ2-C,N–C6H4-1-[(3,5-Me2–C3N2)–CH2–(η5-C5H4)Fe(η5-C5H5)]}Cl(PPh3)] · CH2Cl2

The synthesis and characterization of pyrazole derivatives of general formula [C6H4-4-R-1-{(3,5-Me2–C3N2)–CH2–(η5-C5H4)Fe(η5-C5H5)}] [R = OMe (1a) or H (1b)] with a ferrocenylmethyl substituent are described.The study of the reactivity of compounds 1 with palladium(II) acetate has allowed the isolation of complexes (μ-AcO)2[Pd{κ2-C,N-C6H3-4-R-1-[(3,5-Me2–C3N2)–CH2–(η5-C5H4)Fe(η5-C5H5)]}]2 (2) [R = OMe (2a) or H (2b)] that contain a bidentate [C(sp2, phenyl), N]− ligand and a central “Pd(μ-AcO)2Pd” unit.Furthermore, treatment of 2 with LiCl produced complexes (μ-Cl)2[Pd{κ2-C,N-C6H3-4-R-1-[(3,5-Me2–C3N2)–CH2–(η5-C5H4)Fe(η5-C5H5)]}]2 (3) [R = OMe (3a) or H (3b)] that arise from the replacement of the acetato ligands by the Cl−.Compounds 2 and 3 also react with PPh3 giving the monomeric complexes [Pd{κ2-C,N-C6H3-4-R-1-[(3,5-Me2–C3N2)–CH2–(η5-C5H4)Fe(η5-C5H5)]}X(PPh3)] {X− = AcO− and R = OMe (5a) or H (5b) or X− = Cl− and R = OMe (6a) or H (6b)}, where the phosphine is in a cis-arrangement to the metallated carbon atom. Treatment of 3 with thallium(I) acetylacetonate produced [Pd{κ2-C,N-C6H3-4-R-1-[(3,5-Me2–C3N2)–CH2–(η5-C5H4)Fe(η5-C5H5)]}(acac)] (7) [R = OMe (7a) or H (7b)]. Electrochemical studies of the free ligands and the cyclopalladated complexes are also reported. The dimeric complexes 3 also react with MeO2C–Ctriple bond; length of mdashC–CO2Me (in a 1:4 molar ratio) giving [Pd{(MeO2C–Cdouble bond; length as m-dashC–CO2Me)2C6H3-4-R-1-[(3,5-Me2–C3N2)–CH2–(η5-C5H4)Fe(η5-C5H5)]}Cl] (8) [R = OMe (8a) or H (8b)], which arise from the bis(insertion) of the alkyne into the σ{Pd–C(sp2, phenyl)} bond of 3.