1215770-26-5Relevant articles and documents
Base-promoted selective aryl C-Br and C-I bond cleavage by iridium(III) porphyrin: Reduction of IrIII-OH to IrII for metalloradical ipso substitution of aryl-halogen bonds
Cheung, Chi Wai,Chan, Kin Shing
, p. 4269 - 4283 (2011/10/03)
Base-promoted selective aryl carbon-bromine and carbon-iodine bond (Ar-X, X = Br, I) cleavage by iridium(III) porphyrin carbonyl chloride (Ir III(ttp)(CO)Cl) was achieved in the presence of base (K 2CO3, NaOH) to give iridium(III) porphyrin aryls (Ir III(ttp)Ar). Mechanistic studies revealed that the base undergoes ligand substitution with Ir(ttp)(CO)Cl to yield an iridium(III) hydroxo species (IrIII(ttp)OH). The hydroxo ligand most likely reduces the Ir(III) center to give iridium(II) porphyrin dimer ([IrII(ttp)]2) and H2O2. In a competitive pathway, [Ir II(ttp)]2 disproportionates in the presence of base and residual water to give an iridium(III) hydride (IrIII(ttp)H) and Ir(ttp)OH. In a productive process, [Ir(ttp)]2 undergoes Ir II(ttp) metalloradical-mediated ipso substitution of Ar-X via an addition-elimination pathway to form Ir(ttp)Ar and Ir(ttp)X. Ir(ttp)X is recycled by reacting with base to regenerate [Ir(ttp)]2 for subsequent Ar-X cleavage.
Base-promoted selective aryl C-Cl cleavage by iridium(III) porphyrins via a metalloradical ipso addition-elimination mechanism
Cheung, Chi Wai,Chan, Kin Shing
, p. 4999 - 5009 (2011/11/04)
Base-promoted aryl carbon-chlorine bond (Ar-Cl) cleavage by iridium(III) porphyrin carbonyl chloride (IrIII(ttp)(CO)Cl; ttp = 5,10,15,20-tetrakis(p-tolyl)porphyrinato dianion) was achieved in the presence of K2CO3 to give iridium(III) porphyrin aryls (Ir III(ttp)Ar). Mechanistic studies revealed that K2CO 3 promotes the reduction of Ir(ttp)(CO)Cl to give the iridium(II) porphyrin dimer intermediate [IrII(ttp)2. [Ir(ttp) 2 is the source of IrII(ttp) metalloradical, which cleaves Ar-Cl to give Ir(ttp)Ar and a chlorine radical (Cl?) via radical ipso substitution in an addition-elimination pathway. Cl ? reacts with [Ir(ttp)2 to yield Ir(ttp)Cl for subsequent base-promoted reduction and Ir(ttp) for radical chain propagation. Additionally, the base-promoted Ar-Cl cleavage of chlorobenzene (PhCl) by Ir(ttp)(CO)Cl gives both Ir(ttp)Ph and 1,4-bis-iridium(III)-porphyrin benzene, IrIII(ttp)(p-C6H4)IrIII(ttp). The reactive Cl? can simultaneously react with PhCl via homolytic aromatic substitution to give 1,4-dichlorobenzene, which further undergoes double Ar-Cl cleavage to form Ir(ttp)(p-C6H4)Ir(ttp).
Reactivity studies of iridiuni(III) porphyrins with methanol in alkaline media
Cheung, Chi Wai,Fung, Hong Sang,Lee, Siu Yin,Qian, Ying Ying,Chan, Yun Wai,Chan, Kin Shing
experimental part, p. 1343 - 1354 (2010/05/14)
Ir(ttp)Cl(CO) (la; ttp = 5,10,15,20-tetrakis(p-tolyl)porphyrinato dianion) was found to cleave the C-O bond of CH3OH at 200 C to give Ir(ttp)CH3 (3a). Addition of KOH promoted the reaction rate and gave a higher yield of Ir(ttp)CH3 in 70% yield in 1 day. Mechanistic studies suggest that, in the absence of KOH, Ir(ttp)Cl(CO) reacts with CH 3OH initially to give Ir(ttp)OCH3, which then undergoes β elimination to produce Ir(ttp)H (4a). Ir(ttp)H further reacts slowly to cleave the C-O bond of CH3OH, likely via cr-bond metathesis, to give Ir(ttp)CH3. In the presence of KOH, Ir(ttp)Cl(CO) initially reacts with KOH more rapidly to give Ir(ttp)OH, which then cleaves the 0-H bond of CH3OH by metathesis to give Ir(ttp)OCH3. Ir(ttp)OCH 3 further isomerizes via /3-hydride elimination/reinsertion to give Ir(Up)CH2OH and concurrently undergoes base-assisted /3-proton elimination to give Ir(ttp)-K+ (5a). Ir(ttp)CH.20H subsequently condenses with CH3OH to form. Ir(Up)CH2OCH3 (2). Finally, Ir(ttp)-K+ cleaves the C-O bond in CH3OH, most probably via nucleophilic substitution, to give Ir(ttp)CH3. Ir(ttp)CH 2OCH3 also serves as the precursor of Ir(ttp)-K+ as it undergoes nucleophilic substitution by KOH to give Ir(ttp)-K+.
