Chemistry of the metal carbonyls. Part XLV. Reactions between hexafluorobuta-1,3-diene and the pentacarbonyl hydrides of manganese and rhenium

Abstract

Reaction of pentacarbonylrhenium hydride with hexafluorobuta-1,3-diene gives a crystalline 1 : 1 adduct CHF₂·CF₂·CF:CF·Re(CO)₅(Ia) corresponding to a 1,4-addition followed by a 1,3-fluorine shift. Pentacarbonylmanganese hydride reacts very rapidly with hexafluorobuta-1,3-diene to give four complexes, one of which (Ib) is isostructural with the rhenium complex. The other complexes may be formulated as arising (i) by a 1,2-addition, followed by a 2,4-fluorine shift giving CF₃·CF:C(CHF₂)·Mn(CO)₅(II), (ii) or by a 1,2-addition followed by a hydride shift giving CF₂:CF·CH(CF₃)·Mn(CO)₅(III), and (iii) and acyl complex CHF₂·CF:CF·CO·Mn(CO)₅(IV) probably formed by the capture by water of an allylic intermediate involved in the formation of (Ib). The complexes have been characterised by their n.m.r. and i.r. spectra. The ¹⁹F and ¹H n.m.r. parameters for these and some related fluoro-alkenyl transition-metal complexes are correlated.