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Abstract ortho‐Phosphinophenol (oPP) is an unusual example of an air‐stable primary phosphine and a valuable precursor to a variety of useful organophosphorus compounds. The presence of PH2and OH functionalities offers the possibility of intermolecular and intramolecular P⋅⋅⋅HO hydrogen bonding (HB). The close proximity of these two groups also offers the opportunity for intramolecular PH2⋅⋅⋅HO dihydrogen bonding (DHB). This work provides experimental and computational evidence for these various types of interactions. In the solid state,oPPis associated by significant intermolecular P⋅⋅⋅HO hydrogen bonds as revealed by a single crystal X‐ray structural determination. Multinuclear NMR and IR spectroscopic studies, coupled with DFT computational studies, suggest thatoPPadopts multiple conformations in solution whose nature varies with the identity of the solvent. In the gas phase or non‐polar solvents (such as cyclohexane) an equilibrium between four conformations ofoPPis proposed. Interestingly,in silico, a conformational isomer having bifurcated intramolecular PH2⋅⋅⋅HODHB(PP4) is found to be more stable than a conformational isomer having intramolecular P⋅⋅⋅HOHB(PP1). In polar solvents (S), NMR studies indicate intermolecular OH⋅⋅⋅S HBplays a dominant role in modulating31P NMR chemical shifts over a 17 ppm range.
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Ligand‐Free Ultrasmall Recyclable Iridium(0) Nanoparticles for Regioselective Aromatic Hydrogenation of Phosphine Oxide Scaffolds: An Easy Access to New Phosphine Ligands
Abstract Herein, we developed the recyclable ligand‐free iridium (Ir)‐hydride based Ir0nanoparticles (NPs) for the first regioselective partial hydrogenation of PV‐substituted naphthalenes. Both the isolated and in situ generated NPs are catalytically active. A control nuclear magnetic resonance (NMR) study revealed the presence of metal‐surface‐bound hydrides, most likely formed from Ir0species. A control NMR study confirmed that hexafluoroisopropanol as a solvent was accountable for substrate activation via hydrogen bonding. High‐resolution transmission electron microscopy of the catalyst supports the formation of ultrasmall NPs, and X‐ray photoelectron spectroscopy confirmed the dominance of Ir0in the NPs. The catalytic activity of NPs is broad as showcased by highly regioselective aromatic ring reduction in various phosphine oxides or phosphonates. The study also showcased a novel pathway toward preparingbis(diphenylphosphino)‐5,5′,6,6′,7,7′,8,8′‐octahydro‐1,1′‐binaphthyl (H8‐BINAP) and its derivatives without losing enantioselectivity during catalytic events.
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- Award ID(s):
- 2044778
- PAR ID:
- 10426654
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 62
- Issue:
- 39
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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