A Molecular Complex with a Formally Neutral Iron Germanide Motif (Fe₂Ge₂)

We report the synthesis and isolation of a stable complex containing the formally neutral Fe₂Ge₂ motif, which is stabilized by the coordination of an N-heterocyclic carbene to the germanium and of carbon monoxide to the iron center. [(NHC^{<i>i</i>Pr₂Me₂})­GeFe­(CO)₄]₂ is obtained by reduction of the NHC^{<i>i</i>Pr₂Me₂}-coordinated dichlorogermylene adduct of Fe­(CO)₄, which in turn is obtained from the reaction of Fe₂(CO)₉ with GeCl₂·NHC^{<i>i</i>Pr₂Me₂} (NHC^{<i>i</i>Pr₂Me₂} = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene). The solid-state structure of the title compound reveals two distinct coordination modes for the Fe­(CO)₄ fragments: bridging (π-type) and terminal (σ-type). In solution, the rapid equilibrium between the two modes was resolved by NMR at −35 °C. Reaction with propylene sulfide at room temperature affords the sulfide-bridged digermanium complex with two terminal Fe­(CO)₄ moieties

A Molecular Complex with a Formally Neutral Iron Germanide Motif (Fe₂Ge₂)

We report the synthesis and isolation of a stable complex containing the formally neutral Fe₂Ge₂ motif, which is stabilized by the coordination of an N-heterocyclic carbene to the germanium and of carbon monoxide to the iron center. [(NHC^{<i>i</i>Pr₂Me₂})­GeFe­(CO)₄]₂ is obtained by reduction of the NHC^{<i>i</i>Pr₂Me₂}-coordinated dichlorogermylene adduct of Fe­(CO)₄, which in turn is obtained from the reaction of Fe₂(CO)₉ with GeCl₂·NHC^{<i>i</i>Pr₂Me₂} (NHC^{<i>i</i>Pr₂Me₂} = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene). The solid-state structure of the title compound reveals two distinct coordination modes for the Fe­(CO)₄ fragments: bridging (π-type) and terminal (σ-type). In solution, the rapid equilibrium between the two modes was resolved by NMR at −35 °C. Reaction with propylene sulfide at room temperature affords the sulfide-bridged digermanium complex with two terminal Fe­(CO)₄ moieties

Efficient Preparation of the Esters of Biomass-Derived Isohexides by Base-Catalyzed Transesterification under Solvent-Free Conditions

The monoesters and diesters of glucose-derived isosorbide (IS) have potential applications as sustainable dispersants, surfactants, emulsifiers, monomer units for polymers, and plasticizers. This work reports a solvent-free, high-yielding, and scalable pathway for producing the monoesters and diesters of IS by a transesterification reaction using K2CO3 as an efficient, inexpensive, and recyclable base catalyst. In the case of monoesters, the selectivity toward the exo-monoester of IS was found higher than that toward the endo-monoester. The methodology was successfully extended to synthesize the monoesters and diesters of isomannide and isoidide. The gram-scale preparation of alkyl, vinyl, and aryl esters of isohexides was optimized on the reaction temperature, duration, equivalence of the ester reagent, and catalyst loading. Under optimized conditions (50 mol % K2CO3, 180 °C, 6 h), various aryl and alkyl esters of the isohexides were isolated in satisfactory yields. The unsymmetrical diesters of the isohexides were conveniently synthesized by stepwise transesterification

Stepwise Reversible Oxidation of <i>N</i>‑Peralkyl-Substituted NHC–CAAC Derived Triazaalkenes: Isolation of Radical Cations and Dications

Herein, the isolation and characterization of <i>N</i>-peralkyl-substituted NHC–CAAC derived triazaalkenes in three oxidation states, neutral, radical cation, and dication, are reported. Cyclic voltammetry has shown the reversible electronic coupling between the first and second oxidation to be Δ<i>E</i>_1/2 = 0.50 V. As a proof-of-principle, to demonstrate the electron-rich nature of the triazaalkene, it was shown that it can be used as an electron donor in the reduction of an aryldiazonium salt to the corresponding arene