Synthesis and characterisation of cyclopentadienyl complexes of barium:: precursors for atomic layer deposition of BaTiO3

Cyclopentadienyl complexes Ba(C5Me5)(2)(THF)(2) (1), Ba(C5Me5)(2)(A) (A = THF, dien, trien, diglyme, triglyme) (2-5), Ba((Pr3C5H2)-C-i)(2)(THF)(2) (6), Ba((Bu3C5H2)-C-t)(2)(THF) (7), Ba(Me2NC2H4C5Me4)(2) (8) and Ba(EtOC2H4C5Me4)(2) (9) were prepared and characterised with TGA/SDTA, NMR and MS. Crystal structures of 2, 4, 5, 7, 8 and 9 are presented. All complexes prepared sublime under reduced pressure and complexes 1, 6 and 7 showed volatility also under atmospheric pressure. Complexes 1, 6 and 7 lose the coordinated THF when evaporated while complexes 2-5 are sublimable as complete molecules under reduced pressure. Complexes with bulky cyclopentadienyl ligands (6 and 7) are the most thermally stable and volatile among the prepared barocenes. X-Ray structure determinations reveal that all the complexes studied are monomeric. Complexes 1, 7 and 8 were successfully tested in BaTiO3 thin film depositions by atomic layer deposition (ALD).