The Synthesis of Di-μ-thio-dithio-bis (dialkyldithiocarbamates) Dimolybdenum (V) and Their Effects on Boundary Lubrication

Sulfurized molybdenum dialkyldithiocarbamates prepared from molybdenum trioxide, carbon disulfide, and dialkylamine were separated by chromatography into three components. A new compound, the analytical result of which showed (R2NCSS)2Mo2S4 (where R=ethyl, isopropyl, n-butyl, and isobutyl), was obtained by phosphorus pentasulfide treatment of a xylene solution of sulfurized molybdenum dialkyldithiocarbamate. The mechanism of the pyrolysis of these molybdenum complexes was investigated. EP properties of the complexes blended in Li-12 hydroxystearate grease were tested using a Timken and Shell 4-Ball Machine.Thermogravimetric analysis in a stream of nitrogen indicated that the complexes decomposed in two distinct stages. The first stage decomposition occured at a relatively low temperature because of dealkylation, and the second decomposition occured at a higher temperature. It was confirmed that molybdenum disulfide crystals were formed by the pyrolysis of the complexes in vacuo or in an atmosphere of nitrogen. The complexes blended in the grease showed excellent EP performance and antiwear properties in laboratory bench tests.