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.