This dissertation describes the synthesis and reactions of tungsten thiocarbonyl, thiocarbyne and thiocarbene complexes. Treatment of Bu[subscript]4N (HB(pz)[subscript]3) (CO)[subscript]2W(CS) (HB(pz)[subscript]3[superscript]- is the tris (1-pyrazolyl)borato ligand) with (([eta][superscript]5-C[subscript]9H[subscript]7)Mo(CO)[subscript]2(MeCN)[subscript]2) BF[subscript]4 gives the neutral W-Mo bonded dimer (HB(pz)[subscript]3) (CO)[subscript]2W([mu]-CS)Mo([eta][superscript]5-C[subscript]9H[subscript]7)(CO)[subscript]2. A single-crystal X-ray diffraction study shows that the molybdenum atom achieves an 18-electron configuration by accepting [pi]-electron density from the thiocarbonyl ligand which is also bonded via the carbon to the tungsten. This is the first example of a complex containing a four-electron donating, side-on bridging thiocarbonyl ligand. The thiocarbonyl complex (HC(pz)[subscript]3) (CO)[subscript]2W(CS) is prepared by the reaction of trans-IW(CO)[subscript]4(CS)[superscript]- with HC(pz)[subscript]3. The nucleophilic sulfur atom of the CS ligand can be methylated with Me[subscript]3O[superscript]+ to give the thiocarbyne (HC(pz)[subscript]3) (CO)[subscript]2W≡C-SMe[superscript]+. Reaction of the carbyne with phosphorus nucleophiles (PR[subscript]3) gives the [eta][superscript]2-ketenyl derivatives (HC(pz)[subscript]3) (CO) (R[subscript]3P)[overline]W[C(O)CSMe][superscript]+. Protonation of the carbyne with HBF[subscript]4· Et[subscript]2O produces the [eta][superscript]2-carbene (HC(pz)[subscript]3] (CO)[subscript]2[overline]W[[eta][superscript]2-CH(SMe)] [superscript]2+, which reacts with PR[subscript]3, RS[superscript]- and H[superscript]- nucleophiles to give the carbene adducts (HC(pz)[subscript]3] (CO)[subscript]2[overline]W[[eta][superscript]2-CH(L)(SMe)][superscript] n+. The SMe[superscript]+ electrophile adds to the carbyne carbon of (HB(pz)[subscript]3) (CO)[subscript]2W≡C-SMe, to give (HB(pz)[subscript]3] (CO)[subscript]2[overline]W[[eta][superscript]2-C(SMe)SMe][superscript]+, containing an [eta][superscript]2-dithiocarbene ligand bonded to the metal through both the carbon and one of the sulfur atoms. Reactions of the dithiocarbene complex with nucleophiles (Nuc) give the air stable adducts (HB(pz)[subscript]3] (CO)[subscript]2[overline]W[[eta][superscript]2-C(SMe)(Nuc)SMe] (Nuc = SR, H, CH[subscript]3 and PMe[subscript]3). Heating the MeS[superscript]- dithiocarbene adduct (HB(pz)[subscript]3] (CO)[subscript]2[overline]W[[eta][superscript]2-C(SMe)[subscript]2SMe] above 60 °C results in the loss of CO and C-S bond cleavage, giving the carbyne (HB(pz)[subscript]3) (MeS)[subscript]2W≡C-SMe, which was characterized by X-ray analysis. Thermal and photolytic reactions of the other dithiocarbene adducts also give products resulting from C-S bond cleavage.