Synthesis, structure and reactivity of iridium complexes containing a bis-cyclometalated tridentate C^N^C ligand

Cheung, Wai Man; Chong, Man Chun; Sung, Ho Yung; Cheng, Shun‐Cheung; Williams, Ian D.; Ko, Chi‐Chiu; Leung, Wa Hung

doi:10.1039/d1dt01269j

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“…The reaction chemistry of Ir(C^N^C) complexes is underdeveloped due, in part, to the lack of general methods to synthesize Ir(C^N^C) starting materials that possess a labile coligand or a vacant coordination site at the Ir center. − Coordinately saturated [Ir(C^N^C)(N^N^N)] + and [Ir(C^N^C)(N^C^N)] complexes bearing planar, bis-cyclometalated C^N^C ligands such as 2,6-diphenylpyridine (dppy) have been synthesized by cyclometalation of H 2 C^N^C with [Ir(N^N^N)Cl 3 ] (N^N^N = substituted 2:2′,6′:2″-terpyridine) and [Ir(N^C^N)Cl] 2 (μ-Cl) 2 (HN^C^N = substituted 1,3-di(2-pyridyl)benzene), respectively. The hydride compound [Ir(dppy)(P i Pr 3 ) 2 (H)] has been obtained via C–H activation of 2,6-diphenylpyridine with [Ir(H) 5 (P i Pr 3 ) 2 ] .…”

Section: Introductionmentioning

confidence: 99%

“…The hydride compound [Ir(dppy)(P i Pr 3 ) 2 (H)] has been obtained via C–H activation of 2,6-diphenylpyridine with [Ir(H) 5 (P i Pr 3 ) 2 ] . We have recently synthesized [Ir(C^N^C)(HC^N^C)(CO)] (H 2 C^N^C = 2,6-bis(4- tert -butylphenyl)pyridine) via transmetalation of [Ir(CO) 2 Cl 2 ] − with [Hg(HC^N^C)Cl], and studied its photoisomerization …”

Section: Introductionmentioning

confidence: 99%

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High-Valent Iridium Complexes Containing a Tripodal Bis-Cyclometalated C^N^C Ligand

Cheng

Chan

et al. 2023

Organometallics

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Iridium complexes containing a bis-cyclometalated tripodal C^N^C ligand have been synthesized, and their redox property and reactivity have been studied. The previously reported intermediate (1) prepared from IrCl 3 •xH 2 O and bis(4-(tert-butyl)phenyl)methyl)pyridine (H 2 Bubnpy) has been used as a starting material for synthesis of Ir(C^N^C) complexes. Treatment of 1 with CO, xylNC (xyl = 2,6-dimethylphenyl), PCy 3 (Cy = cyclohexyl), and the Klaüi tripodal ligand Na[Co(η 5 -C 5 H 5 ){P(O)(OEt) 2 } 3 ] (NaL OEt ) afforded [H 3 dtpny][Ir(Bubnpy)(CO)Cl 2 ] (2), [Ir(Bubnpy)(CNxyl) 2 Cl] (3), [Ir(Bubnpy)(PCy 3 )Cl] (4), and [Ir(Bubnpy)(L OEt )] (6), respectively. Reaction of 5-coordinated 4 with CO gave the adduct [Ir(Bubnpy)(PCy 3 )Cl(CO)] (5). Treatment of 1 and 4 with [Ru(L OEt )(N)Cl 2 ] afforded the respective heterometallic μ-nitrido complexes [(H 2 O)Cl(Bubnpy)Ir(μ-N)Ru(L OEt )Cl 2 ] (7) and [(PCy 3 )Cl(Bubnpy)Ir(μ-N)Ru(L OEt )Cl 2 ] (8). The Ir−N [1.887(5) Å] and Ru−N [1.661(5) Å] distances in 7 are indicative of the Ir(V)�N�Ru(IV) resonance structure. The cyclic voltammogram of 6 in CH 2 Cl 2 displayed a reversible couple at ca. 0 V vs Fc +/0 (Fc = ferrocene) that is assigned as the Ir(IV/III) couple. Oxidation of 6 with Ag(OTf) (OTf − = triflate) afforded 6•OTf that exhibited an EPR signal in CH 2 Cl 2 at 4 K with g x = 2.06, g y = 1.91, and g z = 2.84 and Ir(IV) (I = 3/2) hyperfine coupling constants A xx , A yy , and A zz of 60, 40, and 18 G, respectively, consistent with the Ir(IV) formulation. Treatment of 4 with PhICl 2 yielded [Ir(Bubnpy)(PCy 3 )Cl 2 ] (9), whereas the reaction of 7 with PhICl 2 yielded mixed-valence [Cl 2 (Cl 2 Bubnpy)Ir(μ-N)Ru(L OEt )Cl 2 ] (10) that contains a chlorinated C^N^C ligand. DFT calculations indicated that the spin density in 10 is mostly found at the Ir atom, the chloride ligands, and a phenyl ring of the C^N^C ligand. 1 and 4 can catalyze the oxidation of cyclooctene with PhIO, possibly via an Ir-oxo or Ir−PhIO active intermediate. The results of this work highlight the ability of the dianionic tripodal C^N^C ligand to stabilize high-valent iridium.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

High-Valent Iridium Complexes Containing a Tripodal Bis-Cyclometalated C^N^C Ligand

Cheng

Chan

et al. 2023

Organometallics

Self Cite

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Synthesis, structure and reactivity of iridium complexes containing a bis-cyclometalated tridentate C^N^C ligand

Abstract: In an effort to synthesize cyclometalated iridium complexes containing a tridentate C^N^C ligand, transmetallation of [Hg(HC^N^C)Cl] (1) (H2C^N^C = 2,6-bis(4-tert-butylphenyl)pyridine) with various organoiridium starting materials has been studied. The treatment...

Cited by 1 publication

References 80 publications

High-Valent Iridium Complexes Containing a Tripodal Bis-Cyclometalated C^N^C Ligand

High-Valent Iridium Complexes Containing a Tripodal Bis-Cyclometalated C^N^C Ligand

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