386707-40-0Relevant academic research and scientific papers
User-friendly aerobic reductive alkylation of iridium(III) porphyrin chloride with potassium hydroxide: Scope and mechanism
Zuo, Huiping,Liu, Zhipeng,Yang, Wu,Zhou, Zhikuan,Chan, Kin Shing
, p. 20618 - 20625 (2015)
Alkylation of iridium 5,10,15,20-tetrakistolylporphyrinato carbonyl chloride, Ir(ttp)Cl(CO) (1), with 1°, 2° alkyl halides was achieved to give (ttp)Ir-alkyls in good yields under air and water compatible conditions by utilizing KOH as the cheap reducing agent. The reaction rate followed the order: RCl N2 pathway by [IrI(ttp)]-. Ir(ttp)-adamantyl was obtained under N2 when 1-bromoadamantane was utilized, which could only undergo bromine atom transfer pathway. Mechanistic investigations reveal a substrate dependent pathway of SN2 or halogen atom transfer.
Base-Promoted C-O Bond Cleavage of Primary Alcohols by Iridium(III) Porphyrin Chloride
Bian, Yongjun,Qu, Xingyu,Chan, Kin Shing
supporting information, p. 1376 - 1383 (2020/04/20)
Various Ir(por)-benzyls and Ir(por)-alkyls (por = porphyrinato dianion ligand) were successfully synthesized with benzyl and 1° alkyl alcohols by C-O bond cleavage with Ir(ttp)(CO)Cl (ttp = 5,10,15,20-tetraphenylporphyrinato dianion) in alkaline media. The alkylation products were afforded in up to 92% yields. Mechanistic investigations suggest that both the Ir(ttp)- anion and Ir(ttp)H are key intermediates via a hydrogen-borrowing pathway.
Alkyl Carbon-Oxygen Bond Cleavage of Aryl Alkyl Ethers by Iridium-Porphyrin and Rhodium-Porphyrin Complexes in Alkaline Media
Chen, Chen,Chan, Kin Shing
, p. 3456 - 3464 (2017/10/03)
Alkyl C-O bond cleavage in aryl alkyl ethers was achieved with Rh(ttp)Cl (1a; ttp = 5,10,15,20-tetrakis(p-tolyl)porphyrinato dianion) together with competitive alkyl C-H bond activation in alkaline media. In contrast, selective alkyl C-O bond cleavage occurred with the iridium-porphyrin Ir(ttp)(CO)Cl (1b)/KOH. Mechanistic investigations indicate the coexistence of MI(ttp)- and M2II(ttp)2 (M = Rh, Ir) under basic conditions. With a weaker Rh(ttp)-Rh(ttp) bond, RhII(ttp)· metalloradical exists in an appreciable amount to cleave the alkyl C-H bond, competing with the alkyl C-O bond cleavage via RhI(ttp)-. In contrast, the more nucleophilic IrI(ttp)- cleaves the alkyl C-O bond exclusively.
Comparative study of rhodium and iridium porphyrin diaminocarbene and N-heterocyclic carbene complexes
Anding, Bernie J.,Ellern, Arkady,Woo, L. Keith
, p. 2219 - 2229 (2014/06/09)
Iridium meso-tetratolylporphyrinato (TTP) mono- and bis-diaminocarbene complexes, [Ir(TTP)[=C(NHBn)(NHR)]2-x(C≡NBn) x]BF4, where R = Bn, n-Bu and x = 1, 0, were synthesized by nucleophilic addition of amines to the bis-isocyanide complex [Ir(TTP)(C≡NBn)2]BF4. Rhodium and iridium porphyrinato N-heterocyclic carbene (NHC) complexes M(TTP)CH3(NHC), where NHC = 1,3-diethylimidazolylidene (deim) or 1-(n-butyl)-3- methylimidazolylidene (bmim), were prepared by the addition of the free NHC to M(TTP)CH3. The NHC complexes displayed two dynamic processes by variable-temperature NMR: meso-aryl-porphyrin C-C bond rotation and NHC exchange. meso-Aryl-porphyrin C-C bond rotation was exhibited by both rhodium and iridium complexes at temperatures ranging between 239 and 325 K. Coalescence data for four different complexes revealed δ? ROT values of 59 ± 2 to 63 ± 1 kJ·mol -1. These relatively low rotation barriers may result from ruffling distortions in the porphyrin core, which were observed in the molecular structures of the rhodium and iridium bmim complexes. Examination of NHC exchange with rhodium complexes by NMR line-shape analyses revealed rate constants of 3.72 ± 0.04 to 32 ± 6 s-1 for deim displacement by bmim (forward reaction) and 2.7 ± 0.4 to 18 ± 2 s-1 for bmim displacement by deim (reverse reaction) at temperatures between 282 and 295 K, corresponding to δf? of 65.2 ± 0.6 kJ·mol-1 and δr ? of 66.2 ± 0.5 kJ·mol-1, respectively. Rates of NHC exchange with iridium were far slower, with first-order dissociation rate constants of (1.75 ± 0.04) × 10 -4 s-1 for the forward reaction and (1.2 ± 0.1) × 10-4 s-1 for the reverse reaction at 297.1 K. These rate constants correspond to δ? values of 94.2 ± 0.6 and 95.2 ± 0.2 kJ·mol-1 for the forward and reverse reactions, respectively. Equilibrium constants for the exchange reactions were 1.6 ± 0.2 with rhodium and 1.56 ± 0.04 with iridium, favoring the bmim complex in both cases, and the log(K) values for NHC binding to M(TTP)CH3 were 4.5 ± 0.3 (M = Rh) and 5.4 ± 0.5 (M = Ir), as determined by spectrophotometric titrations at 23°C. The molecular structures also featured unusually long metal-Ccarbene bonds for the bmim complexes (Rh-CNHC: 2.255(3) A and Ir-C NHC: 2.194(4) A).
Scope and mechanism of carbonyl carbon and α-carbon bond cleavage of ketones by Iridium(III) porphyrin complexes
Li, Bao Zhu,Fung, Hong Sang,Song, Xu,Chan, Kin Shing
, p. 1984 - 1990 (2011/05/06)
Chemoselective carbonyl carbon and α-carbon bond activation (CCA) of ketones (RCOR) was successfully achieved with various iridium(III) tetrakis-4-tolylporphyrinato complexes Ir(ttp)X (X = (BF4)(CO), Cl(CO), and Me) to give the corresponding Ir(ttp)COR (R = Ar, Me, or Et) and Ir(ttp)R (R = Me or Et) complexes. Ir(ttp)(BF4)(CO) exhibited the highest reactivity toward CCA, as it possesses a higher Lewis acidity in catalyzing the aldol condensation of ketones to give water, which hydrolyzes the kinetic products, C-H bond activation (CHA) complexes, into the proposed Ir(ttp)OH for a subsequent CCA process. The CCA step is nonregioselective in giving both Ir(ttp)R and Ir(ttp)COR. However, Ir(ttp)R was kinetically less stable toward hydrolysis to give Ir(ttp)OH. Thus, only Ir(ttp)COR was observed as the sole CCA product.
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
, 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+.
Base-promoted selective activation of benzylic carbon-hydrogen bonds of toluenes by iridium(III) porphyrin
Cheung, Chi Wai,Chan, Kin Shing
, p. 3043 - 3055 (2009/02/05)
K2CO3 and NaOPh promoted the rate of benzylic carbon-hydrogen bond activation (BnCHA) of toluenes with iridium(III) porphyrin carbonyl chloride (Ir(ttp)Cl(CO)) to give iridium porphyrin benzyls in high yields. Mechanistic studies sug
Selective oxidation of (porphyrinato)iridium(III) arylethyls by nitroxide: Evidence for stabilization of carbon-centered Ir-CH2-CHR radicals by iridium
Yeung, Siu Kwan,Chan, Kin Shing
, p. 6426 - 6430 (2008/10/09)
(Arylethyl)iridium(III) porphyrins were oxidized selectively with excess 2,2,6,6-tetramethylpiperidinoxy (TEMPO) at the benzylic positions to yield (2-aryl-2-oxoethyl)iridium porphyrins. Other alkyl- and PhCH2CH 2CH2-substituted iridium porphyrins did not react or gave complex mixtures and low yields of indium methyl. The proposed intermediate of the carbon-centered IrIII(CH2CHR) radical is probably stabilized by the β iridium center, allowing the (slipped) olefin metalloradical complex IrII(CH2=CHR) as a reasonable resonance structure.
