Photocrystallographic Observation of Halide-Bridged Intermediates in Halogen Photoeliminations
نویسندگان
چکیده
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.
منابع مشابه
Asymmetric hydrogenation of quinazolinium salts catalysed by halide-bridged dinuclear iridium complexes bearing chiral diphosphine ligands.
Asymmetric hydrogenation of quinazolinium salts was catalysed by halogen-bridged dinuclear iridium complexes bearing chiral diphosphine ligands, yielding tetrahydroquinazoline and 3,4-dihydroquinazoline with high enantioselectivity. A derivative of chiral dihydroquinazoline was used as a chiral NHC ligand.
متن کاملHalogen Photoelimination from Dirhodium Phosphazane Complexes via Chloride-Bridged Intermediates.
Halogen photoelimination is a critical step in HX-splitting photocatalysis. Herein, we report the photoreduction of a pair of valence-isomeric dirhodium phosphazane complexes, and suggest that a common intermediate is accessed in the photochemistry of both mixed-valent and valence-symmetric complexes. The results of these investigations suggest that halogen photoelimination proceeds by two sequ...
متن کاملHalogen radicals contribute to photooxidation in coastal and estuarine waters.
Although halogen radicals are recognized to form as products of hydroxyl radical ((•)OH) scavenging by halides, their contribution to the phototransformation of marine organic compounds has received little attention. We demonstrate that, relative to freshwater conditions, seawater halides can increase photodegradation rates of domoic acid, a marine algal toxin, and dimethyl sulfide, a volatile ...
متن کاملDirect evidence of a multicentre halogen bond: unexpected contraction of the P-XXX-P fragment in triphenylphosphine dihalides.
Triphenylhalophosphonium halides, Ph(3)PX(2), form crystals comprising bridged linear cations [Ph(3)P-X-X-X-PPh(3)](+) where the X(3) bridge is shortened from 6.56 Å in Cl-Cl-Cl to 6.37 Å in the Br-Br-Br system. It is proposed that this structure is stabilised by five-centre/six-electron (5c-6e) hypervalent interactions.
متن کاملMetal-catalysed halogen exchange reactions of aryl halides.
Aryl halides are common synthetic targets themselves, and also highly versatile synthetic intermediates. Aryl chlorides are much more widely available and easier to synthesise than the other halide derivatives, so the development of effective methods for interconverting aryl halide derivatives would therefore be extremely useful. This article outlines which transformations are particularly desi...
متن کامل