Thermochimica Acfq 56 (1982) 241-245 Elsevier Scientific Publishing Company, Amsterdam-Printed in The Netherlands 241 Note MASS SPECTRAL AND THERMOGRAVIMETRIC STUDI[ES OF MOLYBDENUM DITHIOCARBAMATES M.R. UDUPA and K.S. NAGARAJA Department of Chemistry, Indian Institute of Technology, Madras-600 036 (India) (Received 5 Januar- 1982) Molybdenum. forms complexes [I] with the dithiocarbamate ligand in almost all oxidation states from 0 to 6. The number of ligand molecules per molybdenum is found to be a maximum of two in the complexes, with the ligand acting as a bidentate chelate. The remaining positions of the molybdenum polyhedra are occupied by ligands such as 02- T S2-, NO+, NCS-, etc. The valence-change concept [2] was proposed to rationalize novel features of the mass spectra of metal complexes as it was observed that the modes of ion dissociation are markedly dependent on the oxidation states usually assumed by the metal atom. Casey et al. [3] have studied the mass spectrum of Mo,0,[(C,H5),NCS,], and confirmed the binuclear na- ture of the complex. Reported in this note are the mass spectral studies of diethyldithiocarbamates of dinitrosyl molybdenum [Mo(NO),(Et,NCS,),], I, oxoisothiocyanatomolybdenum [MoO(NCS)(Et,NCS,)2], II, and the di- merit disulfidomolybdenum [MoS2(Et2NCS2)2]2, III. The results of the thermal decomposition of the complexes in air following thermogravimetry are also included. EXPERIMENTAL Complexes I, II and III were prepared following the reported methods with suitable modifications [4] for better yields. The mass spectra of the complexes were taken on a VG micromass 70-70 FF double focusing mass spectrometer with a VG 2235 data system. The thermal decomposition was carried out on a Stanton recording thermobalance heating rate of 6°C min-‘. RESULTS AND DISCUSSION in air at a continuous Md ybdenwn has seven naturally occurring isotopes spanning from 92 - 100 mass number units. The binuclear molybdenum fragments consist of 15 0040-603 l/82/0000-0000/$02.75 Q 1982 Elsevier Scientific Publishing Company