86372-80-7Relevant academic research and scientific papers
Metal-metal multiple bonds. 14. Synthesis, stereochemistry, and hydrogenation of protonated alkyne adducts of Cp2Mo2(CO)4
Gerlach,Duffy,Curtis, M. David
, p. 1172 - 1178 (1983)
Cp2Mo2(CO)4(Mo≡Mo) reacts with alkynes, RC≡CR′ (R, R′ = H, alkyl, SnMe3, Ph), to form 1:1 adducts Cp2Mo2(CO)4(RC≡CR′) in high yields. Protonation of these alkyne adducts by strong acids (such as CF3COOH, HBF4·Et2O, and HCl) yields compounds with a vinyl group both η1 and η2 bonded to the dimetal fragment. The protonation has been shown to occur in an anti-Markovnikov manner to give the (E)-alkene fragment. X-ray structural analysis of the protonated compounds shows a Mo-Mo single bond with the conjugate base of the acid (in the CF3COOH case) coordinated to one of the molybdenum atoms. For Cp2Mo2(CO)4(PhC≡CH) plus HBF4·Et2O, a H2O adduct is formed upon addition of water. The water molecule was found to be coordinated to one of the molybdenums upon solution of the crystal structure. Cp2Mo2(CO)4(Ph(H)C≡CH)(H 2O)BF4: a = 14.095 (8) A?, b = 9.625 (6) A?, c = 18.176 (10) A?, β = 108.34 (4)°, V = 2341 (2) A?3, Z = 4, space group P21/a. In the CF3COOH adduct, the coordinated trifluoroacetate group is labilized in the presence of excess CF3COOH, suggesting the possibility of facile displacement of coordinated TFA- by groups such as H2. This lability has been utilized in the hydrogenation of 1-hexyne and 1-hexene. The hydrogenation is quantitative when stoichiometric quantities of Cp2Mo2(CO)4 and 1-hexyne are employed. When catalytic quantities of Cp2Mo2(CO)4 and acid are used, then polymerization of the 1-hexyne becomes the favored reaction pathway.
