Palladium(II) complexes containing symmetrical diphosphine ligands based on ferrocene. Sterically enforced palladiumiron bonds

Methylpalladium chloride, cationic methyl- and acylpalladium triflate complexes were synthesised containing bis(dialkyl) and bis(diphenyl)phosphine ferrocene ligands. Trans-coordinated cationic methylpalladium complexes containing 1,1′-bis(di-tert-butylphosphino)ferrocene, form a palladiumiron bond. The less bulky 1,1′-bis(di-iso-propylphosphino)ferrocene ligand coordinates in a cis fashion in methylpalladium chloride complexes. A palladiumiron bond was indicated in the cationic acylpalladium complexes of both alkylphosphine ligands. 1,1′-Bis(diphenylphosphino)ferrocene does not form a palladiumiron bond in the monocationic acyl- and methylpalladium complexes. The complexes were characterised by 1H-, 31P-, 13C-NMR spectroscopy, elemental analysis, and UV–vis spectroscopy.