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-Me-2-C3N2)-CH2-(eta(5)-C5H4)Fe(eta(5)-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 (mu-AcO)(2)[Pd{kappa(2)-C,N-C6H3-4-R-1-[(3,5-Me-2-C3N2)-CH2-(eta(5)-C5H4)Fe(eta(5)-C5H5)]}](2) (2) [R = OMe (2a) or H (2b)] that contain a bidentate [C(sp(2), phenyl), N] ligand and a central "Pd(mu-AcO)(2)Pd" unit. Furthermore, treatment of 2 with LiCl produced complexes (mu-Cl)(2)[Pd{kappa(2)-C,N-C6H3-4-R-1-[(3,5-Me-2-C3N2)-CH2-(eta(5)-C5H4)Fe(eta(5)-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{kappa(2)-C,N-C6H3-4-R-1-[(3,5-Me-2-C3N2)-CH2-(eta(5)-C5H4)Fe(eta(5)-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{kappa(2)-C,N-C6H3-4-R-1-[(3,5-Me-2-C3N2)-CH2-(eta(5)-C5H4)Fe(eta(5)-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-C C-CO2Me (in a 1:4 molar ratio) giving [Pd{(MeO2C-C C-CO2Me) 2C6H3-4-R-1-[(3,5-Me-2-C3N2)-CH2-(eta(5)-C5H4)Fe(eta(5)-C5H5)]}Cl] (8) [R = OMe (8a) or H (8b)], which arise from the bis(insertion) of the alkyne into the sigma{Pd-C(sp(2), phenyl)} bond of 3. (C) 2008 Elsevier B.V. All rights reserved.