Asymmetry-Induced Redistribution in Sn(IV)-Ti(IV) Hetero-Bimetallic Alkoxide Precursors and Its Impact on Thin-Film Deposition by Metal-Organic Chemical Vapor Deposition

With an aim to enhance the stability and volatility of the heterometallic derivative [SnCl4(mu-OEt)(2)Ti(OEt)(2)(HOEt)(2)] (A), obtained conveniently and quantitatively as a simple adduct formula from the equivalent reaction of commercially available SnCl4 and Ti(OEt)(4) in toluene/ethanol, its modification with 2,2,6,6-tetramethyl-3,5-heptanedione (thdH) is reported. The modified precursor [SnCl4(mu-OEt)(2)Ti(thd)(OEt)(HOEt)] (1), obtained from an equimolar reaction of A and thdH, is stable at room temperature but rearranges on heating into A and [SnCl4(mu-OEt)(2)Ti(thd)(2)] (2), as confirmed by vapor pressure measurements and density functional theory calculations. The heterometallic 2 can be obtained in excellent yield from the reaction of A and thdH in a 1:2 molar ratio and is stable in the solid and solution phase up to 200 degrees C. However, the asymmetric nature of its structure consisting of fragments of titanium beta-diketonate and tin chloride connected by bridging ethoxo groups leads to its breakdown into two homometallic components in the gas phase, leading to the deposition of tin-rich metal oxide films on the substrate.