Molybdenum(II) chloride reacts with various unidentate ligands to form complexes [(Mo6Cl8)Cl4L2] whose ultraviolet spectra are closely similar to those of the parent chloride and the acid H2[(Mo6Cl8)Cl6],8H2O. The electrolytic conductivities of the freshly-dissolved complexes are low. The importance of six-co-ordination to the Mo6Cl8 cluster is shown by the existence of complexes [(Mo6Cl8)Cl3(PPh3)3]Cl and [(Mo6Cl8)Cl2(PPh3)2(EtOH)2]Cl2 which are, respectively, 1 : 1 and 2 : 1 electrolytes. Bipyridyl, o-phenanthroline, and o-phenylenebis(dimethylarsine) give complexes of the type [(Mo6Cl8)X2L2]X2(X = Cl or I) which are also 2 : 1 electrolytes. Terpyridyl yields derivatives [(Mo6Cl8)X3terpy]X. Evidence on the mode of co-ordination of these ligands is discussed.