Syntheses of monomeric iron and manganese complexes using bulky tripodal ligands: catalytic alkene epoxidations

Cyclometalation of dimethylaminomethylferrocene by the sulfoxide complexes cis-[PdCl2(OSMeR)2] (R=Me, Ph, and C6H4Me-4) occurs in methanol or methylene chloride as solvent, the highest yields being 35, 25 and 15% in the series, respectively. The reaction affords complexes trans(N,S)-[Pd{(2-Me2NCH2C5H3)Fe(C5H5)}Cl(OSMeR)] and the structure of the palladacycle with R=Me was established in the X-ray crystal study. Bound via sulfur, the sulfoxides dissociate in solution demonstrating, in contrast to the analogous Pt(II) complexes, extremely low affinity to palladium(II) centers. The latter effect is considered to be crucial to account for the failure to carry out attempted asymmetric cyclopalladation of dimethylaminomethylferrocene by the complex with the enantiomerically pure ligand R(+)-methyl p-tolyl sulfoxide.