title: Stereoelectronic Effects in Cl2Elimination from Binuclear Pt(III) Complexes.
abstract: Halogen photoelimination is the critical energy-storing step of metal-catalyzed HX-splitting photocycles. Homo- and heterobimetallic Pt(III) complexes display among the highest quantum efficiencies for halogen elimination reactions. Herein, we examine in detail the mechanism and energetics of halogen elimination from a family of binuclear Pt(III) complexes featuring meridionally coordinated Pt(III) trichlorides. Transient absorption spectroscopy, steady-state photocrystallography, and far-infrared vibrational spectroscopy suggest a halogen elimination mechanism that proceeds via two sequential halogen-atom-extrusion steps. Solution-phase calorimetry experiments of the meridional complexes have defined the thermodynamics of halogen elimination, which show a decrease in the photoelimination quantum efficiency with an increase in the thermochemically defined Pt-X bond strength. Conversely, when compared to an isomeric facial Pt(III) trichloride, a much more efficient photoelimination is observed for the fac isomer than would be predicted based on thermochemistry. This difference in the fac vs mer isomer photochemistry highlights the importance of stereochemistry on halogen elimination efficiency and points to a mechanism-based strategy for achieving halogen elimination reactions that are both efficient and energy storing.
authors: Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States.|Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States.
authors: David C
authors: DC
authors: Powers
authors: Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
authors: Seung Jun
authors: SJ
authors: Hwang
authors: Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
authors: Bryce L
authors: BL
authors: Anderson
authors: Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States.
authors: Haifeng
authors: H
authors: Yang
authors: Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
authors: Shao-Liang
authors: SL
authors: Zheng
authors: ChemMatCARS, The University of Chicago , Argonne, Illinois 60439, United States.
authors: Yu-Sheng
authors: YS
authors: Chen
authors: University at Buffalo, The State University of New York , Buffalo, New York 14260, United States.
authors: Timothy R
authors: TR
authors: Cook
authors: Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States.
authors: François P
authors: FP
authors: Gabbaï
authors: Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
authors: Daniel G
authors: DG
authors: Nocera