The Reaction of Iron Acetylides with Carbon Dioxide

Abstract

The acetylido iron hydride trans-[FeH(CCH)(depe) 2 ] reacts with an excess of CO 2 at ambient pressure and temperature to form a five-membered metalalactone cis-[Fe(OC(O)CHCH-κ 2 C,O)(depe) 2 ]. The reaction appears to proceed by electrophilic addition of CO 2 to the β-carbon of the coordinated acetylide and cyclization to form the metalalactone product. At low temperature, a second molecule of CO 2 is incorporated to give a carboxy-substituted metalalactone cis-When the initial metal acetylido hydride is substituted at the β-acetylenic carbon, the addition of CO 2 results in a metalalactone where the substituent is in the position adjacent to the carbonyl in the metalalactone ring.

Recent developments on the transformation of CO2utilising ligand cooperation and related strategies

“…Similar observations were also found for the corresponding complexes containing bis(diethylphosphino) ethane as a co-ligand. 77 Similar oxidative coupling transformations, where alkenes are utilised as the AB coupling unit, have been observed across a range of other transition metals. Selected examples are highlighted in Scheme 15.…”

“…Similar observations were also found for the corresponding complexes containing bis(diethylphosphino)ethane as a co-ligand. 77…”

Iron-Mediated C–C Bond Formation via Reductive Coupling with Carbon Dioxide

“…Additionally, the C(23)–O(1) and C(23)–O(2) bond lengths of 1.291(2) and 1.241(2) indicated partial delocalization of the carboxylate π-bond. Iron metallocycles related to 6 have been previously studied by X-ray diffraction, , though 6 is the first parent lactone derived from CO 2 -ethylene coupling to be structurally characterized.…”

Coordination Chemistry of (Triphos)Fe(0) Ethylene Complexes and Their Application to CO2 Valorization

“…Recently, Field and co-workers described the coupling of CO 2 with various acetylides mediated by low-valent iron dmpe (dmpe = 1,2-bis­(dimethylphosphino)­ethane) and depe (depe = 1,2-bis­(diethylphosphino)­ethane) complexes, in which unsaturated iron lactones were isolated and characterized (Figure ). , While much of the reactivity of the depe and dmpe variants was analogous, important differences in the regioselectivity of the CO 2 coupling were observed with ancillary ligand changes. The dmpe iron complex coupled CO 2 and phenylacetylene to selectively produce an α-substituted unsaturated lactone, while the more sterically hindered depe iron complex produced exclusively β-substituted lactones (Figure ).…”

“…The dmpe iron complex coupled CO 2 and phenylacetylene to selectively produce an α-substituted unsaturated lactone, while the more sterically hindered depe iron complex produced exclusively β-substituted lactones (Figure ). Using the depe chelate, our own laboratory has reported that (depe) 2 Fe­(C 2 H 4 ) produces an isolable five-membered saturated metallalactone species via coupling of CO 2 and C 2 H 4 ( A ; Figure ). Upon addition of a proton source, complex A liberates propionic acid .…”