Base-Free Transfer Hydrogenation with an Ionic-Liquid-Supported Ruthenium η6-Arene Bis(pyrazolyl)methane Catalyst

BICAAC-Derived Covalent and Cationic Ir(I) Complexes: Application of Ir(BICAAC)Cl(COD) Complexes as Catalysts for Transfer Hydrogenation and Hydrosilylation Reactions

The ambiphilic bicyclic (alkyl)(amino)carbenes (Me/iPrBICAAC) upon reaction with [IrCl(COD)]2 smoothly afford mononuclear Ir(I) complexes that have been spectroscopically and structurally characterized. These complexes exhibit good catalytic activity for transfer hydrogenation (TH) of 4-chlorobenzaldehyde using isopropyl alcohol (iPrOH), with turnover frequency values ranging between 6269 and 8093 h-1. Choosing the covalent complex Ir(MeBICAAC)Cl(COD) as a catalyst, a wide array of carbonyls and imines functionalized with electron-withdrawing and electron-donating substituents have been surveyed and afforded their reduced products in moderate-to-good yields. No detachment of the BICAAC unit from the Ir center was observed upon prolonged heating of Ir(MeBICAAC)Cl(COD) in toluene-d8 or isopropyl alcohol-d8, which evidenced good thermal stability of the catalyst. Complex Ir(MeBICAAC)Cl(COD) was also found to be catalytically active for the hydrosilylation of a variety of aldehydes using triethylsilane (Et3SiH).

Ionic Liquids: Advances and Applications in Phase Transfer Catalysis

Ionic liquids are a family of liquids that are composed entirely of ions and usually have melting points lower than 100 °C. Extensive research, along with the ever-growing interest of the scientific community, allowed for the development of a multitude of ionic liquids with low melting points. Such compounds are considered neoteric materials as well as ideal, custom-made solvents for a variety of different chemical transformations. In this regard, the importance of phase transfer catalysis is evident in a diversity of substrates and reactions. The use of phase transfer catalysts allows the reaction to proceed, facilitating the transfer of otherwise insoluble reactants to the desired phase. Recent scientific advances led to the emergence of ionic liquids, which are excellent candidates as phase transfer catalysts. The inherent fine-tuning capability of these molecules, along with the potential of phase transfer catalytic reactions, epitomize the sustainable aspect of this field of research. Herein, a cohesive report of such applications will be presented, including the period from the last decade of the 20th century up to date.

Modifying bis(triflimide) ionic liquids by dissolving early transition metal carbamates

The authors report the first modification of ionic liquids with metal carbamates. A selection of homoleptic N,N-dialkylcarbamates of group 4 and 5 metals, M(O₂CNR₂)_n, were dissolved in bis(trifluoromethylsulfonyl)imide-based ionic liquids, i.e. [bmim][Tf₂N] and [P(oct)₄][Tf₂N], at 293 K. The resulting solutions were characterized by means of IR, UV and NMR spectroscopy, and the data were compared to those of the respective metal compounds. Notably, the dissolution process did not proceed with the release of any of the original carbamato ligands, thus preserving the intact coordination frame around the metal centre. The solvation process of Ti(O₂CNⁱPr₂)₄, as a model species, in [bmim][Tf₂N] was rationalized by DFT calculations. As a comparative study, solutions of NbF₅ and MCl₅ (M = Nb, Ta) in [bmim][Tf₂N] were also investigated, revealing the possible occurrence of solvent anion coordination to the metal centres.

Ruthenium p-cymene complexes with α-diimine ligands as catalytic precursors for the transfer hydrogenation of ethyl levulinate to γ-valerolactone

Cationic Ru(ii) arene complexes with α-diimine ligands were investigated as catalytic precursors in the transfer hydrogenation of ethyl levulinate to γ-valerolactone from isopropanol under MW irradiation.