More Like this

1. Iron( iii ) chloride-catalyzed activation of glycosyl chlorides

   https://doi.org/10.1039/C8OB02413H  

   Geringer, Scott A.; Demchenko, Alexei V. (December 2018, Organic & Biomolecular Chemistry)

   Glycosyl chlorides have historically been activated using harsh conditions and/or toxic stoichiometric promoters. More recently, the Ye and the Jacobsen groups showed that glycosyl chlorides can be activated under organocatalytic conditions. However, those reactions are slow, require specialized catalysts and high temperatures, but still provide only moderate yields. Presented herein is a simple method for the activation of glycosyl chlorides using abundant and inexpensive ferric chloride in catalytic amounts. Our preliminary results indicate that both benzylated and benzoylated glycosyl chlorides can be activated with 20 mol% of FeCl 3 . 

   more » « less
2. 2.2.2-Cryptand complexes of neptunium( iii ) and plutonium( iii )

   https://doi.org/10.1039/D1CC05904A  

   Goodwin, Conrad A.; Ciccone, Sierra R.; Bekoe, Samuel; Majumdar, Sourav; Scott, Brian L.; Ziller, Joseph W.; Gaunt, Andrew J.; Furche, Filipp; Evans, William J. (January 2022, Chemical Communications)

   New coordination environments are reported for Np( iii ) and Pu( iii ) based on pilot studies of U( iii ) in 2.2.2-cryptand (crypt). The U( iii )-in-crypt complex, [U(crypt)I 2 ][I], obtained from the reaction between UI 3 and crypt, is treated with Me 3 SiOTf (OTf = O 3 SCF 3 ) in benzene to form the [U(crypt)(OTf) 2 ][OTf] complex. Similarly, the isomorphous Np( iii ) and Pu( iii ) complexes were obtained similarly starting from [AnI 3 (THF) 4 ]. All three complexes (1-An; An = U, Np, Pu) contain an encapsulated actinide in a THF-soluble complex. Absorption spectroscopy and DFT calculations are consistent with 5f 3 U( iii ), 5f 4 Np( iii ), and 5f 5 Pu( iii ) electron configurations. 

   more » « less
3. A Stiboranyl Platinum Triflate Complex as an Electrophilic Catalyst

   https://doi.org/10.1021/acs.organomet.0c00193  

   You, Di; Smith, Jesse E.; Sen, Srobona; Gabbaï, François P. (April 2020, Organometallics)

   With the view of developing electrophilic late-transition-metal catalysts, we have now synthesized [(o-(Ph2P)C6H4)2Sb(OTf)2]Pt(OTf) (2) and [(o-(iPr2P)C6H4)2Sb(OTf)2]Pt(OTf) (4) by treatment of the corresponding trichlorides ([(o-(R2P)C6H4)2SbCl2]PtCl (R = Ph, iPr)) with 3 equiv of AgOTf. The crystal structures of 2 and 4 confirmed that the chloride ligands have been fully substituted by more labile triflate ligands. Despite structural similarities in the dinuclear cores of 2 and 4, only 2 acts as a potent carbophilic catalyst in enyne cyclization reactions. The high activity of 2 is also reflected by its ability to promote the addition of pyrrole and thiophene derivatives to alkynes. Structural and computational analyses suggest that the superior reactivity of 2 results from both favorable steric and electronic effects. Finally, a comparison of 2 with the previously reported self-activating catalyst [(o-(Ph2P)C6H4)2Sb(OTf)2]PtCl underscores the benefits of triflate for chloride substitution. 

   more » « less
4. Cyclopentadienone Iridium Bipyridyl Complexes: Acid-Stable Transfer Hydrogenation Catalysts

   https://doi.org/10.1021/acs.organomet.3c00266  

   Marron, Daniel P.; Galvin, Conor M.; Waymouth, Robert M. (August 2023, Organometallics)

   The synthesis, structure, and reactivity of a series of cyclopentadienone and hydroxycyclopentadienyl 4,4’-dimethylbipyridine (dmbpy) iridium complexes (C5Tol2Ph2O)(dmbpy)IrCl 1, [(C5Tol2Ph2OH)(dmbpy)IrCl][OTf] 2 (C5Tol2Ph2O)(dmbpy)IrH 3, and [(C5Tol2Ph2OH)(dmbpy)IrH][OTf] 4 are described. The Ir(I) complexes 1 and 3 are active catalyst precursors for transfer hydrogenation of aldehydes, ketones, and N-heterocycles with HCO2H/Et3N under mild conditions. Model studies implicate the cationic iridium hydride, [(C5Tol2Ph2OH)(dmbpy)IrH][OTf] 4 as a key intermediate, as 4 reacts readily with acetone to generate isopropanol. Selectivity over hydrogenation of alkenes is enhanced compared to other Shvo-type catalysts, and only modest C=C hydrogenation observed when adjacent to polarizing functional groups. Catalytic hydrogenation likely proceeds by a metal-ligand bifunctional mechanism similar to related cyclopentadienone complexes 

   more » « less
5. A unique series of chromium( iii ) mono-alkynyl complexes supported by tetraazamacrocycles

   https://doi.org/10.1039/d1dt00707f  

   Schuman, Ashley J.; Robey, Sarah F.; Judkins, Eileen C.; Zeller, Matthias; Ren, Tong (April 2021, Dalton Transactions)

   null (Ed.)

   Described herein is the synthesis and characterization of macrocyclic Cr III mono-alkynyl complexes. By using the meso -form of the tetraazamacrocycle HMC (HMC = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane), trans -[Cr(HMC)(C 2 Ph)Cl]OTf ( 1a ), trans -[Cr(HMC)(C 2 Np)Cl]OTf ( 2a ), trans -[Cr(HMC)(C 2 C 6 H 4 t Bu)Cl]OTf ( 3a ), and trans -[Cr(HMC)(C 2 (3,5-Cl 2 C 6 H 3 ))Cl]OTf ( 4a ) complexes have been realized. These complexes were synthesized in high yield through the reaction of trans -[Cr( meso -HMC)(C 2 Ar) 2 ]OTf ( 1b–4b ) with stoichiometric amounts of methanolic HCl. Single crystal X-ray diffraction showed that the trans -stereochemistry and pseudo-octahedral geometry is retained in the desired mono-alkynyl complexes. The absorption spectra of complexes 1a–4a display d–d bands with distinct vibronic progressions that are slightly red shifted from trans -[Cr(HMC)(C 2 Ar) 2 ] + with approximately halved molar extinction coefficients. Time-delayed measurements of the emission spectra for complexes 1a–4a at 77 K revealed phosphorescence with lifetimes ranging between 343 μs ( 4a ) and 397 μs ( 1a ). The phosphorescence spectra of 1a–4a also exhibit more structuring than the bis-alkynyl complexes due to a strengthened vibronic coupling between the Cr III metal center and alkynyl ligands. 

   more » « less