title: Photocrystallographic observation of halide-bridged intermediates in halogen photoeliminations.
abstract: Polynuclear transition metal complexes, which frequently constitute the active sites of both biological and chemical catalysts, provide access to unique chemical transformations that are derived from metal-metal cooperation. Reductive elimination via ligand-bridged binuclear intermediates from bimetallic cores is one mechanism by which metals may cooperate during catalysis. We have established families of Rh2 complexes that participate in HX-splitting photocatalysis in which metal-metal cooperation is credited with the ability to achieve multielectron photochemical reactions in preference to single-electron transformations. Nanosecond-resolved transient absorption spectroscopy, steady-state photocrystallography, and computational modeling have allowed direct observation and characterization of Cl-bridged intermediates (intramolecular analogues of classical ligand-bridged intermediates in binuclear eliminations) in halogen elimination reactions. On the basis of these observations, a new class of Rh2 complexes, supported by CO ligands, has been prepared, allowing for the isolation and independent characterization of the proposed halide-bridged intermediates. Direct observation of halide-bridged structures establishes binuclear reductive elimination as a viable mechanism for photogenerating energetic bonds.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
authors.forename: David C
authors.initials: DC
authors.lastname: Powers
authors.forename: Bryce L
authors.initials: BL
authors.lastname: Anderson
authors.forename: Seung Jun
authors.initials: SJ
authors.lastname: Hwang
authors.forename: Tamara M
authors.initials: TM
authors.lastname: Powers
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Pérez
authors.forename: Michael B
authors.initials: MB
authors.lastname: Hall
authors.forename: Shao-Liang
authors.initials: SL
authors.lastname: Zheng
authors.forename: Yu-Sheng
authors.initials: YS
authors.lastname: Chen
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Nocera
mesh_terms: D002384:Catalysis; D003460:Crystallization; D006219:Halogens / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D055668:Photochemical Processes; D011789:Quantum Theory; D012238:Rhodium / Q000737:chemistry*
chemical_list: D006219:Halogens; D009942:Organometallic Compounds; D012238:Rhodium