Fluorinated dienes in transition-metal chemistry – the rich chemistry of electron-poor ligands

Abstract

The coordination chemistry of alkenes is among the fundamentals of organometallic chemistry. However, despite the beneficial effects of fluorination to organic molecules, their fluorinated counterparts are rarely found in transition-metal complexes and most examples are limited to simple monoalkenes like tetrafluoroethene. The paucity of fluorodiene complexes is contrasted by their structural diversity. Seemingly similar dienes containing conjugated, isolated or cumulated double bonds exhibit largely different ligand properties. While the most prominent group, the conjugated fluorodienes, is very flexible in hapticity, their analogues bearing isolated double bonds behave more like monoalkenes. Fluorinated cumulenes in contrast are thermally labile, their chemistry is dominated by the stabilising effect of metal coordination. This review outlines the synthesis, structure and reactivity of transition-metal complexes derived from fluorinated dienes.

From ferrocene to 1,2,3,4,5-pentafluoroferrocene: halogen effect on the properties of metallocene

“…14,15 In organometallic and coordination chemistry, the combination of small size,electron withdrawing and -electron donating properties of fluorine has been used to finely tune the electronic characteristics of ligands and hence the properties of the resulting metal complexes. [16][17][18] Despite these interests and the role of metallocenes in many of these areas of fundamental and applied interest, few polyfluorometallocenes have been described, and structureproperty relationships are limited in scope. [19][20][21] Concerning η 6 coordination compounds, a few arene-vanadium, 22 chromium [23][24][25][26][27][28] and -rhodium 29,30 complexes with up to six fluorine atoms on the aromatic ring have been reported.…”

Binuclear hexafluorocyclopentadiene iron carbonyls: bis(dihapto) versus trihapto–monohapto bonding in iron–iron bonded structures

“…This difference between the behaviors of cyclopentadiene, C 5 H 6 , and its perfluorinated derivative C 5 F 6 is an excellent example of the effects of fluorination on the structure, bonding, and chemical reactivity of ligands bound to transition metal centers. [10][11][12] These known binuclear iron and cobalt derivatives of hexafluorocyclopentadiene 1,2 (Fig. 1) have metal-metal distances far too long for any direct metal-metal bonding.…”

Fluorine Migration from Carbon to Iron and Fluorine–Iron Dative Bonds in Octafluorocyclohexadiene Iron Carbonyl Chemistry

“…Each CC double bond of the hexafluorocyclopentadiene ligand is coordinated to a separate iron atom in the latter complex. Kühnel and Lentz have reviewed the chemistry of the metal complexes of fluorinated diolefins …”