Molecular precursors for the preparation of main group metal oxide and transition metal pnictide thin films have been developed. This work involves the design and synthesis of single-source precursors that contain all the elements required in the thin film. Design of the ideal precursor presents a significant challenge since they must be volatile, non-toxic and thermally stable. Therefore the precursors have been tailored to give clean, reproducible decomposition leading to high quality thin films with good coverage of the substrate. In this review key aspects of precursor synthesis and thin film deposition developed in our group are described. The range of precursors developed for main group oxides, in particular gallium and indium oxide, are discussed, with the most studied being the donor-functionalized alkoxides of the type [R2M(OR′)]2 (M = Ga, In; R = H, Me, Et; R′ = CH2CH2NMe2, CH2CH2OMe etc.). Preliminary mechanistic studies suggest that monomers are formed in the gas phase via stabilization of the metal centre by the donor atom (N or O). Precursors to transition metal pnictides have also been developed, including guanidinates, imides, phosphine and arsine compounds and an overview of their use in film deposition is given.