132296-97-0Relevant academic research and scientific papers
Coupling of two ethyne molecules at rhodium versus coupling of two rhodium atoms at ethyne. 2. Implications for the reactivity. Catalytic and stoichiometric functionalization reactions of ethyne
Bianchini, Claudio,Meli, Andrea,Peruzzini, Maurizio,Vacca, Alberto,Vizza, Francesco
, p. 645 - 651 (1991)
The rhodacyclopentadiene complex [(triphos)RhCl(η2-C4H4)] (3) has been synthesized by treatment of [(triphos)RhCl(C2H4)] (1) in CH2Cl2 with an excess of ethyne (triphos = MeC(CH2PPh2)3). Complex 3 catalyzes under very mild conditions the cyclotrimerization of ethyne to benzene as well as the cyclocooligomerization of ethyne with acetonitrile to 2-picoline. A plausible catalysis cycle for both reactions is proposed on the basis of multiform experimental evidence. Complex 3 is a potential synthon for the preparation of a variety of heterocyclic compounds containing the C4H4 diene moiety. As an example, 3 reacts with dimethyl acetylenedicarboxylate, carbon disulfide, and cyclo-octasulfur, producing dimethyl phthalate, dithiopyrone, and thiophene, respectively. Carbon monoxide reacts with 3 in the presence of TlPF6, yielding [(triphos)Rh(η4-C4H4CO)]PF6 (10), which contains an unsubstituted cyclopentadienone ligand. By treatment with H2, 3 transforms into the η4-butadiene derivative [(triphos)Rh(η4-C4H6)]BPh4 (13). The chemistry of 3 has been compared to and contrasted with that of the related perpendicular μ-C2H2 complex [(triphos)Rh(μ-Cl)(μ-η2,η2-C 2H2)Rh(triphos)]Cl (2). From this study it is concluded that coupling of two or more metal centers at acetylene may lead to inactive complexes for catalytic transformations of acetylene.
