Intramolecular and Intermolecular N−H···C₅H₅^- Hydrogen Bonding in Magnesocene Adducts of Alkylamines. Implications for Chemical Vapor Deposition Using Cyclopentadienyl Source Compounds

Magnesocene adducts of alkylamines were prepared and characterized. Treatment of 3-amino-2,4-dimethylpentane, isopropylamine, tert-butylamine, benzylamine, or N-isopropylbenzylamine with magnesocene at ambient temperature in toluene afforded the amine adducts Cp2Mg(NH2CH(CH(CH3)2)2) (91%), Cp2Mg(NH2iPr) (80%), Cp2Mg(NH2tBu) (67%), Cp2Mg(NH2CH2Ph) (80%), and Cp2Mg(NH(CH(CH3)2)(CH2C6H5)) (91%). These adducts are stable at ambient temperature, and Cp2Mg(NH2CH(CH(CH3)2)2) can be sublimed at 60 °C/0.05 Torr without any evidence for reversion to magnesocene. The solid-state structure of Cp2Mg(NH2CH(CH(CH3)2)2) contains η5- and η2-cyclopentadienyl ligands, and the hydrogen atoms on the coordinated amine nitrogen atom participate in intramolecular and intermolecular hydrogen bonding to the η2-cyclopentadienyl ligand. The observed hydrogen bonding is relevant to the path by which cyclopentadiene is eliminated from metal cyclopentadienyl CVD source compounds during film growth employing acidic element hydrides as co-reactants.