Influence of trans axial ligands on five-coordinate .sigma.-bonded metalloporphyrins. Structural, electrochemical, and spectral investigations of (OEP)Ir(C3H7)(L) complexes

Kadish, Karl M.; Cornillon, J. L.; Mitaine, P.; Deng, Yi‐Fei; Korp, James D.

doi:10.1021/ic00312a008

Cited by 14 publications

(18 citation statements)

References 4 publications

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“…The molecular structure of 17 was confirmed by singlecrystal X-ray diffraction (Figure 2 complex 17 are both shorter than the Ir−P bond distance (2.537 Å) reported for the porphyrinic iridium phosphine complex (OEP)Ir(C 3 H 7 )(PPh 3 ). 52 This unusually long Ir−P bond length was attributed to the trans influence of the alkyl ligand and to steric repulsion between the bulky PPh 3 ligand and the octaethylporphyrin ligand.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Addition of Amines to a Carbonyl Ligand: Syntheses, Characterization, and Reactivities of Iridium(III) Porphyrin Carbamoyl Complexes

et al. 2014

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Treatment of (carbonyl)chloro(meso-tetra-p-tolylporphyrinato)iridium(III), (TTP)Ir(CO)Cl (1), with excess primary amines at 23 °C in the presence of Na2CO3 produces the trans-amine-coordinated iridium carbamoyl complexes (TTP)Ir(NH2R)[C(O)NHR] (R = Bn (2a), n-Bu (2b), i-Pr (2c), t-Bu (2d)) with isolated yields up to 94%. The trans-amine ligand is labile and can be replaced with quinuclidine (1-azabicyclo[2.2.2]octane, ABCO), 1-methylimidazole (1-MeIm), triethyl phosphite (P(OEt)3), and dimethylphenylphosphine (PMe2Ph) at 23 °C to afford the hexacoordinated carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (for R = Bn: L = ABCO (3a), 1-MeIm (4a), P(OEt)3 (5a), PMe2Ph (6a)). On the basis of ligand displacement reactions and equilibrium studies, ligand binding strengths to the iridium metal center were found to decrease in the order PMe2Ph > P(OEt)3 > 1-MeIm > ABCO > BnNH2 ≫ Et3N, PCy3. The carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L = RNH2 (2a,b), 1-MeIm (4a)) undergo protonolysis with HBF4 to give the cationic carbonyl complexes [(TTP)Ir(NH2R)(CO)]BF4 (7a,b) and [(TTP)Ir(1-MeIm)(CO)]BF4 (8), respectively. In contrast, the carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L = P(OEt)3 (5a), PMe2Ph (6a,c)) reacted with HBF4 to afford the complexes [(TTP)Ir(PMe2Ph)]BF4 (9) and [(TTP)IrP(OEt)3]BF4 (10), respectively. The carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L = RNH2 (2a-d), 1-MeIm (4a), P(OEt)3 (5b), PMe2Ph (6c)) reacted with methyl iodide to give the iodo complexes (TTP)Ir(L)I (L = RNH2 (11a-d), 1-MeIm (12), P(OEt)3(13), PMe2Ph (14)). Reactions of the complexes [(TTP)Ir(PMe2Ph)]BF4 (9) and [(TTP)IrP(OEt)3]BF4 (10) with [Bu4N]I, benzylamine (BnNH2), and PMe2Ph afforded (TTP)Ir(PMe2Ph)I (14), (TTP)Ir[P(OEt)3]I (13), [(TTP)Ir(PMe2Ph)(NH2Bn)]BF4 (16), and trans-[(TTP)Ir(PMe2Ph)2]BF4 (17), respectively. Metrical details for the molecular structures of 4a and17 are reported.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Addition of Amines to a Carbonyl Ligand: Syntheses, Characterization, and Reactivities of Iridium(III) Porphyrin Carbamoyl Complexes

et al. 2014

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“…23 Similar hyper spectra were observed previously with the diazoacetate chemistry of iridium porphyrin complexes, including the metal−carbene and metal−ylide intermediates detected in Ir(TTP)CH 3 -catalyzed C−H insertion and N−H insertion reactions, respectively. 14,15,24 In contrast, the diaminocarbene complexes of rhodium (1) and iridium (3 and 4) did not display hyper spectra, suggesting that NHC complexes 5 and 6 provide a better model for the electronic structure of metal−carbene intermediates involved in catalysis than do the diaminocarbene complexes. Transition metal hyperporphyrin complexes are typically classified as d-type metalloporphryins, where the hyper character is the result of ligand-to-metal charge transfer (LMCT) from porphyrin a 1u (π), a 2u (π) orbitals to metal e g (d π ) orbitals.…”

Section: Synthesis and Characterization Of Diaminocarbenementioning

confidence: 95%

Comparative Study of Rhodium and Iridium Porphyrin Diaminocarbene and N-Heterocyclic Carbene Complexes

2014

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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 CC bond rotation and NHC exchange. meso-Aryl-porphyrin CC 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 ΔG⧧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 ΔGf⧧ of 65.2 ± 0.6 kJ•mol-1 and ΔGr⧧ 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 ΔG⧧ 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) Å and Ir-CNHC: 2.194(4) Å).

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“…Two sulfoxide-metalloporphyrin X-ray crystal structures with sulfur-to-metal coordination have been reported. One is an Ir(II) complex of OEP in which DMSO is coordinated trans to a σ-bonded propyl group, 61 and the second is a Ru(II)-TPP complex containing two axial S-coordinated diethyl sulfoxide ligands. 62 The metal ion in both of these complexes is categorized as soft.…”

Section: Predicting the Mode Of Ligand Coordination In The Dmso-acmp8mentioning

confidence: 99%

Comparison of Thioethers and Sulfoxides as Axial Ligands for N-Acetylmicroperoxidase-8: Implications for Oxidation of Methionine-80 in Cytochrome c

et al. 2003

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Methionine-80 (Met-80) in mitochondrial cytochrome c (cyt c) can be oxidized to the corresponding sulfoxide by reactive oxygen species, a reaction of potential biological significance. As an approach to investigating how oxidation of Met-80 would influence its interactions with heme iron, we have examined binding of 2-(methylthio)ethanol (MTE) and dimethyl sulfoxide (DMSO), models for the side chains of Met and Met(SO), respectively, to ferrous and ferric N-acetylmicroperoxidase-8 (AcMP8). We find that DMSO coordinates 1.2 kcal/mol less strongly to Fe(III)-AcMP8 than does MTE, although both ligands form low-spin complexes. Comparison of spectroscopic data for the DMSO complex of Fe(III)-AcMP8 with published data for the Met(SO)-80 form of ferric cyt c allows us to conclude that Met(SO)-80 does not coordinate to iron in the latter. DMSO coordinates to Fe(II)-AcMP8 1.3 kcal/mol more strongly than does MTE, whereas Met-80 and Met(SO)-80 are reported to have approximately equal affinity for Fe(II) in cyt c. This result suggests that the steric environment near the heme iron in cyt c discriminates against coordination of Met(SO)-80. Vacuum quantum chemical density functional theory calculations confirm the greater affinity of the sulfoxide and show that coordination via oxygen is strongly favored. Resonance Raman spectroscopic data indicate that the preference for coordination via oxygen is maintained in solution. The computational data further indicate that the DMSO complex derives significant enthalpic stabilization from pi back-bonding but that iron to sulfur pi back-bonding does not make a significant contribution to bonding in the thioether complex.

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Influence of trans axial ligands on five-coordinate .sigma.-bonded metalloporphyrins. Structural, electrochemical, and spectral investigations of (OEP)Ir(C3H7)(L) complexes

Cited by 14 publications

References 4 publications

Addition of Amines to a Carbonyl Ligand: Syntheses, Characterization, and Reactivities of Iridium(III) Porphyrin Carbamoyl Complexes

Addition of Amines to a Carbonyl Ligand: Syntheses, Characterization, and Reactivities of Iridium(III) Porphyrin Carbamoyl Complexes

Comparative Study of Rhodium and Iridium Porphyrin Diaminocarbene and N-Heterocyclic Carbene Complexes

Comparison of Thioethers and Sulfoxides as Axial Ligands for N-Acetylmicroperoxidase-8: Implications for Oxidation of Methionine-80 in Cytochrome c

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