phosphine-substituted carbonyl complexes of ni have been prepared. the reaction between nic12.6h20, nabh4 or nabh3cn and either pph3 or a series of phosphines of the type ph2p-(ch2)n-pph2 (n=1-5) and also cis-dppe under co atmospheres have been studied under a range of experimental conditions. the important factors which affect the reaction pathways are; the ratio of metal: phosphine: nabh4 or nabh3cn, the rate of addition of reducing agent, the temperature and the duration of reaction. complexes with bridging and monocoordinated dppm were obtained, while with dppe, complexes with bridging, chelating and monocoordinated phosphine were obtained. hetero and homobimetallic complexes have been prepared from mono-coordinated bis-phosphine complexes and were characterized by a variety of spectroscopic methods, by x-ray powder diffraction and in one instance by a single crystal x-ray diffraction study. (see document for full abstract)