Heavier carbon subchalcogenides C3E2 (E = S, Se) can bind to, transition metals through either a C=C or a C=E double bond. These two binding modes on a reactive tungsten (PMe3)(4)WCl2 site have been explored by density functional theory methods (M06-L/DZP+Lanl2DZ). The important step contraling the reaction direction is the initial binding of the C3E2 ligand. Of particular significance is the M=C=C=C=E fragment resulting from the C=E coordination mode. This fragment can bind to additional C3E2 molecules or bridge to other metals. Ultimately C3E2 Serves as a source of C-3 units for building C-3n carbon sp-hybridized allotropes.