Different coordination modes of a 1,1′,2,2′-ferrocenyl-tetraphosphine:: bi- and tri-dentate behaviour with group 6 and 7 transition metals

The behaviour of 1,1', 2,2'-tetrakis(diphenylphosphino)-4,4'-di( tert-butyl) ferrocene (1), acting as a homoannular or heteroannular ligand, has been studied. Due to the cisoid disposition of the phosphino groups of each ring, different coordination modes are observed. With group 6 metal carbonyls, M( CO) 6, the tetraphosphine acts exclusively as a tridentate ligand. In contrast, the reaction with MnCp(CO)(3) leads to complexes showing 1,1' and 1,2 bidentate coordination modes. All these complexes have been characterised by H-1 and P-31 NMR spectroscopy. The molecular structures of the molybdenum complex [(1)Mo(CO)(3)] (2b) and the 1,1' manganese complex [(1)MnCp(CO)] (3) have been established by X-ray diffraction.