Abstract The preparation of cis-[Mo (CO) 4 (biL)](biL denotes 2, 2′-bipyridine-x, x′- dicarbonitrile, x, x′= 4, 5) is reported. Reaction of these complexes with [W (CO) 5 (THF)] produces [MoW 2 (CO) 14 (biL)]. The synthesis of [W 2 CO) 10 (biL)](biL, x, x′= 5) is also reported. The ligands and complexes have been characterised by spectroscopy (IR, electronic absorption, NMR) and microanalysis. The synthesis of biL is significantly ...