Contact

  • Academic
    University - Student Department: Chemistry Position: Graduate

Additional Info

  • Mail Code: 5080

All Publications

  • Ring-Opening Polymerization of Cyclic Esters and Carbonates with (Thio)urea/Cyclopropenimine Organocatalytic Systems. ACS macro letters Morodo, R., Dumas, D. M., Zhang, J., Lui, K. H., Hurst, P. J., Bosio, R., Campos, L. M., Park, N. H., Waymouth, R. M., Hedrick, J. L. 2024: 181-188

    Abstract

    Organocatalyzed ring-opening polymerization is a powerful tool for the synthesis of a variety of functional, readily degradable polyesters and polycarbonates. We report the use of (thio)ureas in combination with cyclopropenimine bases as a unique catalyst for the polymerization of cyclic esters and carbonates with a large span of reactivities. Methodologies of exceptionally effective and selective cocatalyst combinations were devised to produce polyesters and polycarbonates with narrow dispersities (D = 1.01-1.10). Correlations of the pKa of the various ureas and cyclopropenimine bases revealed the critical importance of matching the pKa of the two cocatalysts to achieve the most efficient polymerization conditions. It was found that promoting strong H-bonding interactions with a noncompetitive organic solvent, such as CH2Cl2, enabled greatly increased polymerization rates. The stereoselective polymerization of rac-lactide afforded stereoblock poly(lactides) that crystallize as stereocomplexes, as confirmed by wide-angle X-ray scattering.

    View details for DOI 10.1021/acsmacrolett.3c00716

    View details for PubMedID 38252690

  • Contrasting Roles of Counterions in Anionic Ring-Opening Polymerization Mediated by Heterocycle Organocatalysts ACS CATALYSIS Zhang, J., Lui, K., Jadrich, C. N., Jia, Y., Arrechea, P. L., Hedrick, J. L., Waymouth, R. M. 2023; 13 (24): 16097-16104

    View details for DOI 10.1021/acscatal.3c04772

    View details for Web of Science ID 001142879500001

  • Bimetallic, Silylene-Mediated Multielectron Reductions of Carbon Dioxide and Ethylene. Angewandte Chemie (International ed. in English) Whited, M. n., Zhang, J. n., Conley, A. M., Ma, S. n., Janzen, D. n., Kohen, D. n. 2020

    Abstract

    A metal/ligand cooperative approach to reduction of small molecules by metal silylene complexes (R2Si=M) is demonstrated, whereby silicon activates the incoming substrate and mediates net two-electron transformations via one-electron redox processes at two metal centers. An appropriately tuned cationic pincer cobalt(I) complex featuring a central silylene donor reacts with CO2 to afford a bimetallic siloxane featuring two Co(II) centers with liberation of CO, and reaction with ethylene yields a similar bimetallic complex with an ethylene bridge. Experimental and computational studies suggest a plausible mechanism proceeding via [2+2]-cycloaddition to the silylene complex that is quite sensitive to steric environment. The Co(II)/Co(II) products are further reactive to oxidation and reduction. Taken together, these findings demonstrate a strategy for metal/ligand cooperative small-molecule activation that is well-suited to 3d metals.

    View details for DOI 10.1002/anie.202011489

    View details for PubMedID 32991759

  • Cooperative CO2 Scission by Anomalous Insertion into a Rh-Si Bond ORGANOMETALLICS Whited, M. T., Zhang, J., Donnell, T. M., Eng, V. H., Peterson, P. O., Trenerry, M. J., Janzen, D. E., Taylor, B. H. 2019; 38 (22): 4420–32

    View details for DOI 10.1021/acs.organomet.9b00556

    View details for Web of Science ID 000500038800008

  • Synthesis and Reactivity of Pincer-Type Cobalt Silyl and Silylene Complexes ORGANOMETALLICS Zhang, J., Foley, B. J., Bhuvanesh, N., Zhou, J., Janzen, D. E., Whited, M. T., Ozerov, O. V. 2018; 37 (21): 3956–62

    View details for DOI 10.1021/acs.organomet.8b00594

    View details for Web of Science ID 000450374500035

  • Silylene-assisted hydride transfer to CO2 and CS2 at a [P2Si]Ru pincer-type complex DALTON TRANSACTIONS Whited, M. T., Zhang, J., Ma, S., Nguyen, B. D., Janzen, D. E. 2017; 46 (43): 14757–61

    Abstract

    The synthesis and characterization of base-stabilized and base-free pincer-type bis(phosphine)/silylene [P2Si]Ru complexes are reported. The base-free complex readily reduces CO2 and CS2via silylene-assisted hydride transfer, affording structurally distinct products with silicon-to-ruthenium formate and dithioformate bridges.

    View details for DOI 10.1039/c7dt03659k

    View details for Web of Science ID 000414775000009

    View details for PubMedID 29052677