The reactions of linear conjugated diynes with Dicarbonyl(η-cyclopentadienyl)- cobalt and -rhodium

Abstract

The reactions of (η-C₅H₅)Co(CO)₂ with the diynes hexa-2,4-diyne and 1,4- diphenylbutadiyne give three isomers of the cyclopentadienone complexes (C₅H₅)Co[(RC₂C₂R)₂CO], R = Me or Ph, and two isomers of the tris-alkyne complexes (C₅H₅)₂Co₂(RC₂C₂R)₃CO, R = Me or Ph. Organic products of formula (RC₂C₂R)₃, R = Me or Ph, (MeC₂C₂Me)₅, and (PhC₂C₂Ph)₃CO have been isolated also. Two isomers of (RC₂C₂R), were separated and were identified as the 1,2,4-(R)₃-3,5,6-(C₂R)₃- and the 1,3,5-(R)₃-2,4,6-(C₂R)₃-benzenes. The compound (PhC₂C₂Ph)₃CO is believed to be tris(phenylethynly)triphenylcycloheptatrienone, and (MeC₂C₂Me)₅ is probably a polycyclic aromatic compound. Thermal degradation of the complexes (C₅H₅)₂CO₂(RC₂C₂R)₃CO gives the substituted benzenes (RC₂C₂R)₃.     The reaction of (η-C₅H₅)Rh(CO)₂ and hexa-2,4-diyne gives the cyclopentadienone complex(C₅H₅)Rh[(MeC₂C₂Me)₂CO] and the cycloheptatrienone complex (C₅H₅)Rh[(MeC₂C₂Me)₃CO].Two isomers of the substituted benzene (MeC₂C₂Me)₃ were obtained also.