Reagents to remove oxygen from metal oxyhalide precursors in thin film deposition processes

A process for gas phase deposition of a metal or metal nitride film on a surface substrate comprises: reacting a metal-oxo or metal oxyhalide precursor with an oxophilic reagent in a reactor containing the substrate to deoxygenate the metal-oxo or metal oxyhalide precursor, and forming the metal or metal nitride film on the substrate through a vapor deposition process. The substrate is exposed to the metal oxyhalide precursor and the oxophilic reagent simultaneously or sequentially. The substrate is exposed to a reducing agent sequentially after deoxygenation.