Reaction of GeCl4 and CyPH2 leads to a range of products from which crystals of [CyPH3](+)[GeCl3](-) have been obtained. The major intermediate in this reaction, Cy(H) PGeCl3, can be obtained as the dominant product only when an excess of GeCl4 is used in the preparation. Similarly, crystals of [Ph2PH2](+)[GeCl3](-) have been obtained from reaction of Ph2PH and GeCl4 ( 1 : 1). The structures of both primary and secondary phosphonium cations are reported. Aerosol-assisted and low-pressure chemical vapour deposition experiments using Cy(H) PGeCl3 as precursor lead to the deposition of thin films containing both germanium and phosphorus, contaminated with large amounts of oxygen. GeP has been identified as components of the film from bandgap measurements.