Photocatalysis of Chloroform Decomposition by Hexachloroosmate(IV)

Abstract

Hexachloroosmate(IV) effectively catalyzes the photodecomposition of chloroform in aerated solutions. The decomposition products are consistent with a mechanism in which excited state OsCl(6)(2-) reduces chloroform, rather than one involving photodissociation of chlorine atoms. Trace amounts of ethanol or water in the chloroform lead to photosubstitution to form OsCl(5)(EtOH)(-) or OsCl(5)(H(2)O)(-), neither of which is photocatalytically active.

Photodecomposition of Chloroform Catalyzed by Unmodified MCM‐41 Mesoporous Silica

“…Because carbon–chlorine bond fission occurs during the photocatalyzed decomposition of carbon tetrachloride in ethanol , one might expect an analogous bond fission to occur when chloroform is photocatalytically decomposed, yet this clearly does not occur with MCM‐41 as the catalyst because if it did, the termination products from CHCl 2 radicals would have been found .…”

“…Much of the recent work in our laboratory has been on the catalyzed decomposition of chloroalkanes (29)(30)(31)(32)(33)(34)(35)(36); thus, we have followed with special interest the published work on the photodecomposition of chloroalkanes and chloroarenes by modified mesoporous silica (27,(37)(38)(39)(40)(41)(42)(43)(44). These studies have incorporated a wide variety of modifications.…”

Photocatalysis of Chloroform Decomposition by the Hexachlororuthenate(IV) Ion

“…To complete the cycle, the iron must be reoxidized, from which process more radicals may be generated. A second route to radicals is the photoreduction of the solvent, which is thought to occur with OsCl 6 2− as the catalyst :…”

“…While these and other mechanisms lead to photocatalyzed decomposition, the situation is often complicated by a transformation of the original chlorometallate complex to another species under irradiation , which can greatly obscure mechanistic conclusions.…”

“…A complex that does appear to catalyze chloroform decomposition in this way is [Ru(bpy) 2 Cl 2 ] + , which, when excited, apparently oxidizes ClÀ to Cl (17). *Corresponding author email: phoggard@scu.edu (Patrick E. Hoggard) While these and other (1,4) mechanisms lead to photocatalyzed decomposition, the situation is often complicated by a transformation of the original chlorometallate complex to another species under irradiation (2)(3)(4)18), which can greatly obscure mechanistic conclusions.…”