Transition metal complexes of substituted alkynes. VIII. Complexes of cobalt derived from 1,1,1-Trifluorobut-2-yne

Abstract

The complex Co₄(CO)₁₀(CF₃C₂CH₃) is formed at room temperature from dodecacarbonyltetracobalt and 1,1,1-trifluorobut-2-yne. Another monoalkyne complex Co₂(CO)₆(CF₃C₂CH₃) has been prepared from octacarbonyldicobalt and 1,1,1-trifluorobut-2-yne at room temperature. Treatment with triphenylphosphine converts the complex into Co₂(CO)₄[P(C₆H₅)₃]₂(CF₃C₂CH₃). At 150°, reaction of Co₂(CO)₆(CF3C₂CH₃) and 1,1,1-trifluorobut-2-yne gives a small amount of a purple complex which is believed to be Co₂(CO)₄(CF₃C₂CH₃)₃. Similar reactions involving Co₂(CO)₄(CF₃C₂CH₃) and the alkynes hexafluorobut-2-yne and 3,3,3-trifluoropropyne give the complexes Co₂(CO)₄(CF₃C₂CH₃)(CF₃C₂CF₃)₂ and Co₂(CO)₄(CF₃C₂CH₃)(CF₃C₂H)₂. Spectroscopic studies have led to an assignment of the substitution pattern in these latter complexes. Tris-alkyne complexes were not isolated from similar reactions between 1,1,1-trifluorobut-2-yne and the complexes Co₂(CO)₆(CF₃C₂CF₃) and Co₂(CO)₆(CF₃C₂H). Three isomers of the π-cyclopentadienone-π-cyclopentadienylcobalt complex, [(CF₃C₂CH₃)₂CO]Co(π-C₅H₅), were obtained from (π-C₆H₆)Co(CO)₂ and 1,1,1-trifluorobut-2-yne after U.V. irradiation for several days. The isomers vary in the arrangement of the substituents attached to the cyclopentadienone ring. All reactions involving 1,1,1-trifluorobut-2-yne have been compared with similar reactions involving the related alkynes hexafluorobut-2-yne and but-2-yne.