Reactions of Rhodium Porphyrins with Lactones, Silanes, and Stannanes

Mizutani, Tadashi; Uesaka, Tetsuya; Ogoshi, Hisanobu

doi:10.1021/om00001a049

Cited by 27 publications

(22 citation statements)

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“…Group 9 M I (por) − (M = Rh, Ir; por = porphyrinato dianion) anions show “super nucleophilic” character toward alkyl iodide, lactones, and epoxides in these substitution reactions . The typical method to generate M I (por) − , however, requires an anaerobic atmosphere and expensive NaBH 4 to reduce M III (por)Cl . Recently, our group has developed a more convenient method by using KOH as the reducing agent to generate M I (por) − in aerobic conditions.…”

Section: Introductionmentioning

confidence: 99%

Alkyl Carbon–Oxygen Bond Cleavage of Aryl Alkyl Ethers by Iridium–Porphyrin and Rhodium–Porphyrin Complexes in Alkaline Media

Chen

Chan

2017

Organometallics

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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 M2 II(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.

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Section: Introductionmentioning

confidence: 99%

Alkyl Carbon–Oxygen Bond Cleavage of Aryl Alkyl Ethers by Iridium–Porphyrin and Rhodium–Porphyrin Complexes in Alkaline Media

Chen

Chan

2017

Organometallics

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“…Rhodium and iridium complexes have received much attention for their use in a wide range of chemical transformations, including C–C , and C–H − bond activation and hydrogen-atom-transfer reactions. , In these reactions, paramagnetic Rh and Ir centers could play an important role; however, isolated and well-characterized monomeric species in the 2+ oxidation state are rare compared to their 1+ and 3+ counterparts. Multidentate ligands have been found to successfully stabilize these less accessible rhodium(II) and iridium(II) species. − While rhodium(II) complexes are more often encountered as bimetallic species with bridging ligands and metal–metal bonds, various ligands such as porphyrin-based ligands, , a N , N -bis(2-pyridylmethyl)amine ligand, and pincer ligands have been used to stabilize mononuclear rhodium(II) species. ,,,,− Within this list of complexes, it is rare to find an octahedral monomeric rhodium(II) complex chelated by a tetradentate ligand. , Herein we report the use of Me N4 and t Bu N4 pyridinophane ligands to isolate and full characterize mononuclear Rh I /Ir I (COD) complexes, as well as a rare mononuclear ( Me N4)Rh II complex. The isolation of these complexes allows a direct structural and spectroscopic comparison of group 9 complexes that possess similar geometries and ancillary ligands.…”

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confidence: 99%

Mononuclear Rhodium(II) and Iridium(II) Complexes Supported by Tetradentate Pyridinophane Ligands

2017

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The tetradentate ligands N,N'-dialkyl-2,11-diaza[3,3](2,6)pyridinophane (N4, where R = Me or tBu) were employed to synthesize and fully characterize [(N4)M(COD)] complexes (M = Rh or Ir; COD = cyclooctadiene). Interestingly, these complexes exhibit accessible oxidation potentials and can generate detectable [(N4)M(COD)] complexes, which were characterized by electron paramagnetic resonance and high-resolution electrospray ionization mass spectrometry. Moreover, a rare mononuclear [(N4)Rh(COD)] complex was isolated and crystallographically characterized, allowing for a direct comparison with its rhodium(I) analogue. The detailed characterization of such paramagnetic rhodium(II) and iridium(II) complexes enables further investigation of their redox reactivity.

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“…The two resonances unique to this product are assigned to a rhodium-bound ethyl group in RhEt(Bu 4 saloph) ( 2 ) (eq 1, R = Et). Formation of the ethyl complex in this reaction indicates that the tetralkylammonium ion serves as the source of the alkyl groups in compounds 1 and 2 . , …”

Section: Resultsmentioning

confidence: 92%

“…Further studies of this reaction system utilized two rhodium porphyrins linked by an alkoxy chain in order to modify the interaction of the rhodium centers with methane from a termolecular process to a bimolecular one, and in keeping with the proposed mechanism, this decrease in molecularity boosted the rate of homolytic methane CH activation . Similar radical and radical chain mechanisms have been used to explain other reactions of rhodium porphyrins with hydrogen, olefins, carbon monoxide, alkyl isocyanides, trialkylsilanes, and trialkylstannanes. ,, …”

Section: Introductionmentioning

confidence: 99%

Reactions of the Schiff Base Rhodium Hydride Complex RhH(Bu₄salophen) with Olefins. Observations and Mechanistic Studies

and

Eisenberg

1996

Organometallics

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The tetradentate dianionic Schiff base ligand Bu 4 salophenH 2 reacts with [RhCl(C 2 H 4 ) 2 ] 2 and NR 4 OH (R ) n-Bu, Et) to produce the complexes RhR(Bu 4 salophen) (1, R ) n-Bu; 2, R ) Et), which undergo photolysis (λ > 475 nm) under a hydrogen atmosphere to generate RhH(Bu 4 salophen) (3) and the corresponding alkanes. In benzene at room temperature, olefins insert into the metal-hydride bond ofIn a competition experiment, insertion of styrene is only slightly favored over that of ethylene. For olefinic substrates capable of radical rearrangement (CH 2 dCHR where R ) CH 2 OCH 2 CHdCH 2 and c-C 3 H 5 ), insertion products are formed that do not correspond to radical rearrangements. Specifically, Rh(CH 2 CH 2 OCH 2 CHdCH 2 )(Bu 4salophen) ( 6) is observed as the only product of the reaction of 3 with bis(allyl) ether while Rh(CH 2 CH 2 -c-C 3 H 5 )(Bu 4 salophen) ( 7) is seen as the major product in the reaction with vinylcyclopropane. For the vinylcyclopropane reaction, additional products are also identified by 2D NMR methods as Rh(CH 2 CH 2 CHdCHCH 3 )(Bu 4 salophen) ( 8) and (Bu 4 salophen)Rh-(µ-CH 2 CH 2 CHdCHCH 2 )Rh(Bu 4 salophen) (9). Both the poor selectivity for styrene versus ethylene insertion and the absence of radical rearranged product with bis(allyl) ether and vinylcyclopropane indicate that, in the reaction of 3 with olefins, an intermediate containing a pure carbon-based radical is not involved.

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Reactions of Rhodium Porphyrins with Lactones, Silanes, and Stannanes

Cited by 27 publications

References 0 publications

Alkyl Carbon–Oxygen Bond Cleavage of Aryl Alkyl Ethers by Iridium–Porphyrin and Rhodium–Porphyrin Complexes in Alkaline Media

Alkyl Carbon–Oxygen Bond Cleavage of Aryl Alkyl Ethers by Iridium–Porphyrin and Rhodium–Porphyrin Complexes in Alkaline Media

Mononuclear Rhodium(II) and Iridium(II) Complexes Supported by Tetradentate Pyridinophane Ligands

Reactions of the Schiff Base Rhodium Hydride Complex RhH(Bu₄salophen) with Olefins. Observations and Mechanistic Studies

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Reactions of Rhodium Porphyrins with Lactones, Silanes, and Stannanes

Cited by 27 publications

References 0 publications

Alkyl Carbon–Oxygen Bond Cleavage of Aryl Alkyl Ethers by Iridium–Porphyrin and Rhodium–Porphyrin Complexes in Alkaline Media

Alkyl Carbon–Oxygen Bond Cleavage of Aryl Alkyl Ethers by Iridium–Porphyrin and Rhodium–Porphyrin Complexes in Alkaline Media

Mononuclear Rhodium(II) and Iridium(II) Complexes Supported by Tetradentate Pyridinophane Ligands

Reactions of the Schiff Base Rhodium Hydride Complex RhH(Bu4salophen) with Olefins. Observations and Mechanistic Studies

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Reactions of the Schiff Base Rhodium Hydride Complex RhH(Bu₄salophen) with Olefins. Observations and Mechanistic Studies