N‐Heterocyclic Carbene Iron Silyl Hydride Complexes

Abstract

Reaction of N-heterocyclic carbene iron(0) tetracarbonyl complexes with hydrosilanes (triphenylsilane, methyldiphenylsilane and diphenylsilane) under UV irradiation (350 nm) afforded the octahedral N-heterocyclic carbene iron (II) silyl hydride complexes in yields up to 95 %, resulting from the oxidative addition of the hydrosilane. Eight iron silyl hydrides were obtained and characterized by NMR and X-ray diffraction analysis. Noticeably, the geometry of the ironhydride complexes and the bent structures of the carbonyl ligands were rationalized by DFT calculations.

Iron Catalysis in Reduction and Hydrometalation Reactions

“…Furthermore, experimental evidence proved that the hydrosilylation proceeded via an oxidative addition of various hydrosilanes to unsaturated NHC−Fe species obtained from the complex such as C169 by UV activation, furnishing a hydride−silyl iron complex which was fully characterized by NMR and X-ray analysis. 370 On the basis of these observations, the following mechanism was proposed (Scheme 96): after decoordination of one CO ligand under UV irradiation, oxidative addition of a hydrosilane led to the hydride iron(II) intermediate (X-2). Then insertion of the CO bond of the ester into either Fe−H or Fe−Si was postulated.…”

A Concise Route to Cyclic Amines from Nitroarenes and Ketoacids under Iron‐Catalyzed Hydrosilylation Conditions

“…Thus, the reaction between A and 1 equiv. of PhSiH 3 in deuterated toluene C 7 D 8 at 90 °C for 2 h showed in 1 H‐NMR a representative signal of the Si−H resonance at δ=−9.2 ppm [15e,18a] . Additionally, the 29 Si{ 1 H}‐NMR spectrum of this reaction mixture displayed a signal at δ=−7.4 ppm with a clear shift from the free PhSiH 3 at δ=−59.8 ppm (See Figures S1 and S2 in SI) [18b] .…”

“…The cascade transformation can then be extended to levulinic acid 7. Starting from p-methyl, p-methoxy, pfluoro and p-chloronitrobenzenes, the corresponding N-arylpyrrolidines 8 a-d were produced in 55-66% yields (entries [16][17][18][19]. The reaction can be also performed with 6-oxoheptanoic acid 9 yielding the corresponding N-arylazepane 10 a in 32% yield (entry 20).…”

Iron‐Catalysed Switchable Synthesis of Pyrrolidines vs Pyrrolidinones by Reductive Amination of Levulinic Acid Derivatives via Hydrosilylation

“…Noticeably, as already shown with iron(0) complex B, visible light is crucial to generate a 16 electron active iron(0) species able to promote the oxidative addition of silanes. [22,25] Scheme 2. Possible reaction pathway.…”