Abstract Reactions of five sym-diarylthioureas (L), viz,, sym-diphenylthiourea (dptu), sym-di-o-tolylthiourea (dottu), sym-di-p-tolylthiourea (dpttu), sym-di-o-anisylthiourea (doatu) and sym-di-α- naphthylthiourea (dαntu) with W(CO)6 have been performed both by reflux and ultra-violet irradiation methods in which only monosubstituted products [(L)W(CO)5] are obtained. Several mixed ligand tungsten carbonyl derivatives, viz., [(o-phen or 2,2’-bipy)(L)W(CO)3] and [(Ph3P or Ph3As)(L)W(CO)4] have also been synthesized. Halogenation of [(L)W(CO)5] yielded heptacoordinated [(L)W(CO)4X2] (X = Br or I). The complexes have been characterized by microanalytical data, conductivity and IR measurements. The C-O stretching force constants and CO-CO stretch-stretch interaction constants of [(L)W(CO)5] derivatives have also been evaluated from the IR spectra.