Transition metal thiocarbonyl complex
A transition metal thiocarbonyl complex is a coordination compound containing the ligand CS. Whereas metal carbonyl complexes are very common, even industrially important, only a few dozen thiocarbonyl complexes are known.
Preparation
The main challenge for the preparation of thiocarbonyl complexes arises from the non-availability of carbon monosulfide. Thus, the CS ligand is often extruded from thiocarbonyl-containing precursors. One example involves thiophosgene, which reacts with disodium tetracarbonylferrate:Instead of thiophosgene, chlorothioformates have also been used as a source of CS ligand. The thiocarbonyl analogue of Vaska's complex is prepared in this way.
Carbon disulfide is another source of thiocarbonyl ligands, although CS2 is less electrophilic than thiophosgene and its alkoxy derivative. Carbon disulfide forms η2-CS2 complexes, which are susceptible to desulfurization. This pattern is illustrated by the reaction of Wilkinson's catalyst :
The reaction of with carbon disulfide gives ca 30% yield of, a trimetallic cluster with a triply bridging thiocarbonyl ligands. Many other thiocarbonyl complexes arise from similarly complicated reactions in modest yield.
A variety of other routes have been developed, including addition of sulfur reagents to metal carbyne complexes.