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A Transient Iron Carbide Generated by Cyaphide Cleavage.

Authors :: Wannipurage DC
Yang ES
Chivington AD
Fletcher J
Ray D
Yamamoto N
Pink M
Goicoechea JM
Smith JM
Source :: Journal of the American Chemical Society [J Am Chem Soc] 2024 Oct 02; Vol. 146 (39), pp. 27173-27178. Date of Electronic Publication: 2024 Sep 17.
Publication Year :: 2024
Abstract: Despite their potential relevance as molecular models for industrial and biological catalysis, well-defined mononuclear iron carbide complexes are unknown, in part due to the limited number of appropriate C <subscript>1</subscript> synthons. Here, we show the ability of the cyaphide anion (C≡P <superscript>-</superscript> ) to serve as a C <subscript>1</subscript> source. The high spin ( S = 2) cyaphide complex PhB( <superscript>t</superscript> BuIm) <subscript>3</subscript> Fe-C≡P (PhB( <superscript>t</superscript> BuIm) <subscript>3</subscript> <superscript>-</superscript> = phenyl(tris(3- tert -butylimidazol-2-ylidene)borate) is readily accessed using the new cyaphide transfer reagent [Mg( <superscript>Dipp</superscript> NacNac)(CP)] <subscript>2</subscript> ( <superscript>Dipp</superscript> NacNac = CH{C(CH <subscript>3</subscript> )N(Dipp)} <subscript>2</subscript> and Dipp = 2,6-di(iso-propyl)phenyl). Phosphorus atom abstraction is effected by the three-coordinate Mo(III) complex Mo(N <superscript>t</superscript> BuAr) <subscript>3</subscript> (Ar = 3,5-Me <subscript>2</subscript> C <subscript>6</subscript> H <subscript>3</subscript> ), which produces the known phosphide ( <superscript>t</superscript> BuArN) <subscript>3</subscript> Mo≡P along with a transient iron carbide complex PhB( <superscript>t</superscript> BuIm) <subscript>3</subscript> Fe≡C. Electronic structure calculations reveal that PhB( <superscript>t</superscript> BuIm) <subscript>3</subscript> Fe≡C adopts a doublet ground state with nonzero spin density on the carbide ligand. While isolation of this complex is thwarted by rapid dimerization to afford the corresponding diiron ethynediyl complex, the carbide can be intercepted by styrene to provide an iron alkylidene.