Syntheses and structural studies of two adducts of cadmocene, [CdCp2. TMEDA] and [CdCp2. PMDETA] (TMEDA  Me2NCH2CH2NMe2, PMDETA  (Me2NCH2CH2)2NMe)

Cp 2 Cd.TMEDA 1 and Cp 2 Cd.PMDETA 2 have been synthesized and characterized by spectroscopic studies and by X-ray diffraction studies at low-temperature (153 K). The adducts are present in the crystals as mononuclear complexes. When the denticity of the Lewis base ligands in these adducts is increased (from two in 1 to three in three in 2 ) the Cd 2+ centre requires less electron density from the Cp ligands and the hapticity changes from η 2 − in 1 to η 1 − in 2 . Complexes 1 and 2 are the first compounds for which π-bonding of Cp ligands to Cd 2+ has been observed in the solid state.