Substitution reactions of the bis(benzylthio)acetylene complexes [Tp′Nb(BnSC2SBn)Cl2] and [Tp′Mo(BnSC2SBn)(CO)2](PF6) (Tp′ = hydro-tris(3,5-dimethyl)pyrazolylborate, Bn = benzyl) have been investigated. The coordination of the alkyne ligand turned out to be very stable, while one chloride ion in [Tp′Nb(BnSC2SBn)Cl2], and either one or both of the CO ligands in [Tp′Mo(BnSC2SBn)(CO)2](PF6) can be substituted. The dissociative mechanism of the reactions with [Tp′Mo(BnSC2SBn)(CO)2](PF6) and [Tp′ Mo(BnSC2SBn)(CO)Cl] leads to the primary and exclusive reaction with the solvent. In the course of these studies the structures of [Tp′Nb(BnSC2SBn)Cl2], [Tp′Mo(BnSC2SBn)(CO)(MeCN)](PF6), [Tp′Mo(BnSC2SBn)(CO)Cl] and [Tp′Mo(BnSC2SBn)Cl2][Tp′Mo(BnSC2SBn)ClF] have been determined by X-ray diffraction. Comparison of the closely related compounds allows conclusions how the number of d electrons and the character of the co-ligands influence the alkyne bonding