Two types of rhodium-catalyzed CS/CS metathesis reactions: formation of CS/CS bonds and CC/SS bonds

A rhodium complex catalyzes two types of single bond metathesis reactions of two CS bonds depending on the added ligand: CS/CS to CS/CS metathesis and CS/CS to CC/SS metathesis. In the presence of a catalytic amount of RhH(PPh3)4 and 1,1′-bis(diphenylphosphino)ferrocene (dppf), two 1-alkylthioalkynes exchange alkylthio groups to give equilibrium mixtures of four 1-alkylthioalkynes. When tris(p-methoxyphenyl)phosphine or diphenylmethylphosphine is used, 1,3-butadiynes are obtained.