Dinitrogen Complexes of Bis(cyclopentadienyl) Titanium Derivatives: Structural Diversity Arising from Substituent Manipulation

Dinitrogen coordination to a family of bis(cyclopentadienyl)titanium sandwich complexes, (η5-C5Me4R)2Ti (R = alkyl, aryl, silyl), has been systematically evaluated by in situ solution infrared spectroscopy. The maximum temperature of N2 coordination (Tmax) has been determined as a function of cyclopentadienyl substituent and has been correlated with the structural type (monomer or dimer) of the resulting dinitrogen complex. The electronic properties of each titanium sandwich complex were assessed by infrared spectroscopy of the dicarbonyl derivatives and by the oxidation potentials of the corresponding ferrocenes, (η5-C5Me4R)2Fe. From these data, the thermodynamic preferences for N2 coordination have been established and they increase with smaller, electropositive substituents.