Novel Group II metal MOCVD precursor compositions are described having utility for MOCVD of the corresponding Group II metal-containing films. The complexes are Group II metal .beta.-diketonate Lewis base adducts having ligands such as: (i) amines bearing terminal NH.sub.2 groups; (ii) imine ligands formed as amine (i)/carbonyl reaction products; (iii) combination of two or more of the foregoing ligands (i)-(ii), and (iv) combination of one or more of the foregoing ligands (i)-(ii) with one or more other ligands or solvents. The source reagent complexes of barium and strontium are usefully employed in the formation of barium strontium titanate and other Group II doped thin-films on substrates for microelectronic device applications, such as intearated circuits, ferroelectric memories, switches, radiation detectors, thin-film capacitors, microelectromechanical structures (MEMS) and holoaraphic storage media.