Formation of novel unsaturated fluorinated ligands by metal induced C–C coupling reaction of difluoroallene with fluoromethylidyne ligands of Fe3(CO)9(μ3-CF)2

Nonacarbonyl-bis(μ3-fluoromethylidyne)triiron reacts with 1,1-difluoroallene forming the cluster compounds octacarbonyl(μ3-fluoromethylidyne)-(μ-η1:η3:η1-1,3-difluoro-2-fluoromethylpropane-1,2,3-triyl)triiron (1) and nonacarbonyl(μ-η1:η2:η1-1-fluoro-2-trifluoromethylbut-1-en-1-yl-4-ylidyne)triiron (2). The crystal and molecular structures of both compounds were elucidated by X-ray crystallography. The diferraallyl structure of 1 is similar to that of the products obtained in the reaction of Fe3(CO)9(μ3-CF)2 with various alkynes. However, the formation of 1 requires the migration of fluorine from the CF2 group to the CH2 group forming a difluoromethyl substituent during or after the C–C coupling between the fluoromethylidyne group and the central carbon atom of 1,1-difluoroallene. During the even more complex formation of 2, two carbon carbon bonds between the fluoromethylidyne groups and the allene are formed. Additionally the trifluoromethyl group of 2 is formed by a 1,4-fluorine migration. The unusual 1-fluoro-2-trifluoromethylbut-1-en-1-yl-4-ylidyne ligand bridges a very unsymmetrical triangle of iron atoms with FeFe distances between 2.4917(2) and 2.7497(2) Å, respectively.