The thermolysis of some μ-Alkyne-bis(tricarbonylcobalt) complexes

Abstract

Thermolysis of the μ-alkyne-bis(tricarbonylcobalt) complexes Co₂(CO)₆(C₆F₅C₂C₆F₅), Co₂(CO)₆. (C₆H₅C₂C₆F₅), Co₂(C₆H₂C₂H) , and [ Co₂( CO)₆]₂(C₆H₅C₂C₂C₆H₅) has given a wide range of products. The substituents on the alkyne affect the nature of the products formed in these reactions, and small changes in the thermolysis conditions have a significant effect on the yields of particular products.

Major products formed in the thermal degradation of Co₂(CO)₆(C₆F₅C₂C₆F₅) are the free alkyne C₆F₅C≡CC₆F₅ and the cyclopentadienone C₄(C₆F₅)₄CO. The degradation of CO₂(CO)_6- (C₆H₅C₂C₆F₅) gives two isomers of the cyclopentadienone C₄(C₆H₅)₂(C₆F₅)₂CO and one isomer of the benzene C₆(C₆H₅)₃(C₆F₅)₃. Organometallic complexes of probable formula Co₂(CO)₆ (C₆H₅C₂C₆F₅)₃ and Co(C₆H₅C₂C₆F₄)[C₄(C₆H₅)₂(C₆F₅)₂CO] are also formed in this decomposition reaction. Thermolysis of the terminal alkyne complex Co₂(CO)₆(C₆H₅C₂H) gives 1,2,4-triphenyl- benzene and several complexes of general formula Co₃(CO)₉CY. One of these is the new complex Co₃(CO)₆C₃H₂C₆H₅ which has been separated into two isomers. Degradation of the diyne complex [Co₂(CO)₆]₂(C₆H₅C₂C₆H₅) has given the monoalkyne complex Co₂(CO)₆(C₆H₅C₂C₆H₅) which degrades further to form tetraphenylcyclopentadienone and hexaphenylbenzene. When this degradation is conducted in the presence of some diphenylacetylene, an additional arene of formula C₆(C₆H₅)₅(C₂C₆H₅) can be isolated.