1-Methyl-4-ferrocenylmethyl-3,5-diphenylpyrazole: A versatile ligand for palladium(II) and platinum(II)

The syntheses and characterization of two novel ferrocene derivatives containing 3,5-diphenylpyrazole units of general formula [1-R-3,5-Ph2-(C3N2)-CH2-Fc] {Fc = (η5-C5H5)Fe(η5-C5H4) and R = H (2) or Me (3)} together with a study of their reactivity with palladium(II) and platinum(II) salts or complexes under different experimental conditions is described. These studies have allowed us to isolate and characterize trans-[Pd{1-Me-3,5-Ph2-(C3N2)-CH2-Fc]}2Cl2] (4a) and three different types of heterodimetallic complexes: cis-[M{1-Me-3,5-Ph2-(C3N2)-CH2-Fc]}Cl2(dmso)] {M = Pd (5a) or Pt (5b)}, the cyclometallated products [M{κ2-C,N-[3-(C6H4)-1-Me-5-Ph-(C3N2)]-CH2-Fc}Cl(L)] with L = PPh3 and M = Pd (6a) or Pt (6b) or L = dmso and M = Pt (8b) and the trans-isomer of [Pt{1-Me-3,5-Ph2-(C3N2)-CH2-Fc]}Cl2(dmso)] (7b). In compounds 4a, 5a, 5b and 7b, the ligand behaves as a neutral N-donor group; while in 6a, 6b and 8b it acts as a bidentate [C(sp2,phenyl),N(pyrazole)]− group. A comparative study of the spectroscopic properties of the compounds, based on NMR, IR and UV–Visible experiments, is also reported.

Graphical abstractThe study of the reactivity of the novel ferrocene derivatives containing 3,5-diphenylpyrazole [1-R-3,5-Ph2-(C3N2)-CH2-Fc] {Fc = (η5-C5H5)Fe(η5-C5H4) and R = H (2) or Me (3)}, cis-[MCl2(dmso)2] (M = Pd or Pt, Pd(OAc)2 has allowed to isolate and characterize a wide variety of complexes where the ligands adopt an N-donor or a [C(sp2,phenyl),N(pyrazole)]− mode of binding.Figure optionsDownload full-size imageDownload as PowerPoint slide