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.