Stabilization of Iridium(IV) by Monoanionic Dialkyldiarylguanidinato Ligands

Rohde, Jan-Uwe; Lee, Wei‐Tsung

doi:10.1021/ja9033445

Cited by 32 publications

(26 citation statements)

References 31 publications

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“…The Δ E 1/2 of the first redox step is much lower than those observed in typical iridium(III) complexes. It is, however, comparable to Rhode’s dialkyldiarylguanidinatoiridium(III) complexes ([Ir{ArNC(NR 2 )NAr} 3 ]; Δ E 1/2 = −0.27 to −0.41 V vs Fc/Fc + ) and Crabtree’s mononuclear pyridine–alkoxide iridium(III) system (Δ E 1/2 = −0.18 to −0.69 V vs Fc/Fc + ), − both of which could be oxidized to afford isolable iridium(IV) and/or iridium(V) complexes. The facile oxidation of 4 is likely due to conjugation between the metal d orbitals with the π-rich dpa Ar2 NHC CCC-pincer ligand.…”

Section: Resultsmentioning

confidence: 76%

Synthesis and Isolation of an Anionic Bis(dipyrido-annulated) N-Heterocyclic Carbene CCC-Pincer Iridium(III) Complex by Facile C–H Bond Activation

et al. 2021

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Meridional tridentate N-heterocyclic carbene (NHC)-based pincer ligands contribute to a substantial growth in modern organometallic chemistry in both homogeneous catalysis and luminescence materials. Among all NHC-based pincer ligands, the dianionic LX 2 -type CCC-pincer ones constitute the smallest subcategory owing to their limited ligand frameworks suitable for complexation. This work reports a one-pot, high-yield synthesis of a homoleptic anionic all-carbon bis-pincer iridium(III) complex (4) directly from a bis(aryl)-substituted dipyrido-annulated (dpa Ar2 ) imidazolium salt and [Ir(COD)Cl] 2 via a cascade of deprotonation/C−H activation processes. Both experimental complexation chemistry and computational mechanistic investigation suggest that the large bite angle and π-rich character of the dpa Ar2 NHC are responsible for its facile complexation as a dianionic LX 2type CCC-pincer ligand precursor. The all-carbon ligated iridium(III) complex (4) bearing a π-conjugated ligand scaffold showed remarkably low oxidation potentials, which allows future investigations in its redox chemistry and photophysical properties.

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Section: Resultsmentioning

confidence: 76%

Synthesis and Isolation of an Anionic Bis(dipyrido-annulated) N-Heterocyclic Carbene CCC-Pincer Iridium(III) Complex by Facile C–H Bond Activation

et al. 2021

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“…[10] In contrast, both 1 IV and 2 IV have approximately 0.7 unpaired electrons per Ir and give rhombic EPR signals similar to those of other Ir IV monomers ( Figure S6). [7,11] Thed iamagnetism of 1 V and 2 V indicates an S = 0d 4 Ir V . Prior work showed that having strong donor alkoxides in the same coordination plane favors Ir III to Ir IV oxidation in aseries of Ir(pyalk) 3 and Ir(pyalk) 2 Cl 2 monomers.…”

Section: Angewandte Chemiementioning

confidence: 99%

Synthesis and Characterization of Iridium(V) Coordination Complexes With an N,O‐Donor Organic Ligand

et al. 2017

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We have prepared and fully characterized two isomers of [Ir IV (dpyp) 2 ]( dpyp = meso-2,4-di(2-pyridinyl)-2,4pentanediolate). These complexes can cleanly oxidizet o [Ir V (dpyp) 2 ] + ,w hicht oo ur knowledge represent the first mononuclear coordination complexes of Ir V in an N,O-donor environment. One isomer has been fully characterized in the Ir V state,i ncluding by X-rayc rystallography,X PS,a nd DFT calculations,a ll of which confirm metal-centered oxidation. The unprecedented stability of these Ir V complexes is ascribed to the exceptional donor strength of the ligands,their resistance to oxidative degradation, and the presence of four highly donor alkoxide groups in aplane,which breaks the degeneracy of the d-orbitals and favors oxidation.

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“…Because of its biological interest, guanidine has been used as a ligand for the synthesis of a number of metal complexes; − however, little or no reactivity of these complexes has been reported. We recently reported the synthesis of novel osmium(III) guanidine, mer -[Os{N(H)C(NH 2 ) 2 }( L ) (CN) 3 ] − ( OsG , HL = 2-(2-hydroxyphenyl)benzoxazole) and N -hydroxyguanidine ( mer -[Os{NHC(NH 2 ) (NHOH)}( L ) (CN) 3 ] − , γ -OsGOH ) complexes via the nucleophilic addition of NH 3 and NH 2 OH, respectively, at an osmium(III) hydrogen cyanamide precursor ([Os(NHCN)( L ) (CN) 3 ] 2– , OsNHCN ) (Figure ).…”

Section: Introductionmentioning

confidence: 99%

Dual Pathways in the Oxidation of an Osmium(III) Guanidine Complex. Formation of Osmium(VI) Nitrido and Osmium Nitrosyl Complex

et al. 2017

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The guanidine moiety of arginine is involved in the active sites of a variety of enzymes, such as nitric oxide synthase (NOS) and NiFe hydrogenase. In this paper we aim to investigate the effects of a metal center on the oxidation of guanidine, which should provide an interesting comparison with the biological aerobic oxidation of arginine catalyzed by NOS. We studied the oxidation of an osmium(III) guanidine complex, mer-[Os(L){N(H)C(NH)}(CN)], (OsG, HL = 2-(2-hydroxyphenyl)benzoxazole) by m-chloroperbenzoic acid (m-CPBA), which is potentially an O atom transfer reagent, and by (NH)[Ce(NO)], which is a one-electron oxidant. With m-CPBA, mer-[Os(NO)(L)(CN)] (mer-OsNO) is the product, while with Ce, mer-[Os(N)(L)(CN)] (mer-OsN) is formed instead. The crystal structures of mer-OsNO and mer-OsN were determined by X-ray crystallography. The mechanisms for the oxidation of OsG by m-CPBA and Ce are proposed.

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Stabilization of Iridium(IV) by Monoanionic Dialkyldiarylguanidinato Ligands

Cited by 32 publications

References 31 publications

Synthesis and Isolation of an Anionic Bis(dipyrido-annulated) N-Heterocyclic Carbene CCC-Pincer Iridium(III) Complex by Facile C–H Bond Activation

Synthesis and Isolation of an Anionic Bis(dipyrido-annulated) N-Heterocyclic Carbene CCC-Pincer Iridium(III) Complex by Facile C–H Bond Activation

Synthesis and Characterization of Iridium(V) Coordination Complexes With an N,O‐Donor Organic Ligand

Dual Pathways in the Oxidation of an Osmium(III) Guanidine Complex. Formation of Osmium(VI) Nitrido and Osmium Nitrosyl Complex

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