Reactions of co-ordinated ligands. Part VIII. The addition of hexafluoroacetone to tricarbonyl(diene)iron and η-cyclopentadienyl(diene)rhodium complexes

Abstract

Hexafluoroacetone (HFA) reacts on u.v. irradiation with tricarbonyl(2,3-dimethylbuta-1,3-diene)iron to form a π-allylic iron(II) complex, in which the HFA links the Fe and diene. The corresponding reaction with tricarbonyl(isoprene)iron affords a related species, but which contains two HFA molecules linked head-to-tail. This compound undergoes a rearrangement on heating to form a π-allylic complex containing only one linking HFA, the second HFA molecule becoming a C(CF₃)₂OH group. Isoprene and η-cyclopentadienyl(trans-pentadiene)rhodium react thermally with HFA to form related rhodium(III)π-allylic complexes containing a linking HFA molecule. The analogous reaction with η-cyclopentadienyl(2,3-dimethylbuta-1,3-diene)rhodium affords a similar adduct, which in addition has a second molecule of HFA formally inserted into a cyclopentadienyl carbon–hydrogen bond. 1,3-Disubstitution of the cyclopentadienyl ring occurs in the corresponding reaction of η-cyclopentadienyl[hexamethyl(Dewar)benzene]rhodium.