Iron-molybdenum heterometallic complexes, FeMoO2R4-(H2O) (R=8-quinolinolate, diethyldithiocarbamate, 4-morpholinyl-dithiocarbamate and piperidinyldithiocarbamate), have been prepared from iron(III) molybdate. T.l.c. and x-ray diffraction studies indicate that the complexes are discrete species. The complexes are non-electrolytes in dimethylformamide. Magnetic measurements suggest that the iron and molybdenum are in the III and V oxidation states, respectively, with octahedral geometry around each atom. I.r. spectral studies indicate the presence of MoO3+ and FeOMo bridges and the monoionic bidentate nature of the ligands. Electronic spectral and thermal decomposition studies on these complexes are reported. © 1986 VCH Verlagsgesellschaft mbH.