Transformation of Acetylene to Ethenylidene, Carbene, Acetylide, Vinyl, and Olefin Groups with Cp*Fe(1,2-Cy₂PC₆H₄S)

Abstract

Tautomerization of C 2 H 2 at half-sandwich compound Cp*Fe-(1,2-Cy 2 PC 6 H 4 S) exclusively produces an iron ethenylidene, Cp*Fe-(=C=CH 2 )(1,2-Cy 2 PC 6 H 4 S) (2). Protonation of the ethenylidene causes nucleophilic attack of the C α by sulfur, affording a sulfur-tethered carbene complex, [Cp*Fe=C(CH 3 )SC 6 H 4 PCy 2 ] + (3 +). This Fischer-type carbene complex undergoes an unusual isomerization by migrating a hydrogen atom from the β-CH 3 group to the α-C, leading to the formation of an olefin complex [Cp*Fe(η 4 -CH=CH 2 SC 6 H 4 PCy 2 ] + (4 + ). Compound 2 also displays diverse redox reactivities. It transforms to a neutral acetylide ferric complex (5) when reacting with free radical scavengers and to a cationic vinyl complex [Cp*Fe(η 3 -C(=CH 2 )SC 6 H 4 PCy 2 ] + (6 + ) upon 1e − oxidation. The interconversion between the vinyl and acetylide complexes can be realized through protonation/ deprotonation reactions.

Synthesis and Characterization of Bridging-Diazene Diiron Half-Sandwich Complexes: The Role of Sulfur Hydrogen Bonding

“…The product was obtained as a black solid in 78% yield. In contrast to 2 , which is a paramagnetic species with μ eff = 2.94 μ B in C 6 D 6 , complex 1 is diamagnetic. The methyl protons of the Cp* ring were observed at δ 1.62(s) in 1 H NMR spectrum, while the protons of the quinolinethiolate ligand were well-resolved in the range of δ 5.96–8.53 (Figure S1).…”