Synthesis of iridium complexes with novel planar chiral chelating imidazolylidene ligands (original) (raw)
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Organometallics, 2015
Iridium(III) complexes with a trifunctional pincer ligand containing protic N-heterocyclic carbene (pNHC), pyridine, and imine donor groups were obtained in two sequential steps: (i) protonation of 2-(1-(2,6-diisopropylphenylimino)ethyl)-6-(1-imidazolyl)pyridine (L CH ; the superscript specifies the position of the tautomerizable H atom in the imidazole ring) with HBF 4 •Et 2 O to give the imidazolium salt [HL CH ] + [BF 4 ] − (protonation always occurs at the imidazole N atom) and (ii) metalation of the latter with [Ir(cod)(μ-Cl)] 2 to give the hydrido pincer complex [Ir(H)(Cl)(NCMe){L NHκ 3 N imine ,N Py ,C NHC }] + [BF 4 ] − (3 + [BF 4 ] −). Substitution of MeCN in 3 + [BF 4 ] − by treatment with triisopropylphosphine gave the analogue [Ir(H)(Cl)P(i-Pr) 3 {L NH-κ 3 N imine ,N Py ,C NHC }] + [BF 4 ] − (4 + [BF 4 ] −). Chloride abstraction from 3 + [BF 4 ] − by AgBF 4 gave [Ir(H)(NCMe) 2 {L NH-κ 3 N imine ,N Py ,C NHC }] 2+ [BF 4 − ] 2 (5 2+ [BF 4 − ] 2). The centrosymmetric dinuclear Ir(III) complex [Ir(H)(NCMe){μ-(L CH −H)-κ 3 N imine ,N Py ,C2,κN3}] 2 2+ [B-(C 6 F 5) 3 F − ] 2 (6 2+ [B(C 6 F 5) 3 F − ] 2) was obtained after deprotonation of 5 2+ [BF 4 − ] 2 with KO-t-Bu, followed by addition of B(C 6 F 5) 3. It contains two Ir pincer moieties, each with a N imine ,N Py ,C2 donor set, which are connected by the Ir−N bonds involving the imidazolide rings, leading to a μ-C,N bridging mode for the latter. Remarkably, all of the donor atoms in the tetradentate bridging chelating ligands are chemically different. The molecular structures of 3 + [BF 4 ] − •CH 2 Cl 2 , 4 + [BF 4 ] − •CH 2 Cl 2 , 5 2+ [BF 4 − ] 2 •2CH 2 Cl 2 , and 6 2+ [B(C 6 F 5) 3 F − ] 2 •4CH 2 Cl 2 have been determined by X-ray diffraction.
Iridium(I) and Iridium(III) Complexes Supported by a Diphenolate Imidazolyl-Carbene Ligand
Organometallics, 2010
Deprotonation of 1,3-di(2-hydroxy-5-tert-butylphenyl)imidazolium chloride (1a) followed by reaction with chloro-1,5-cyclooctadiene Ir(I) dimer affords the anionic Ir(I) complex [K][{OCO}Ir(cod)] (2: OCO = 1,3-di(2-hydroxy-5-tert-butylphenyl)imidazolyl; cod = 1,5-cyclooctadiene), the first Ir complex stabilized by a diphenolate imidazolyl-carbene ligand. In the solid state 2 exhibits squareplanar geometry, with only one of the phenoxides bound to the metal center. Oxidation of 2 with 2 equiv of [FeCp 2 ][PF 6 ] generates the Ir(III) complex [{OCO}Ir(cod)(MeCN)][PF 6 ] (3). Reaction of 3 with H 2 results in the liberation of cyclooctane and a species capable of catalyzing the hydrogenation of cyclohexene to cyclohexane. Displacement of cyclooctadiene from 3 can be achieved by heating in acetonitrile to form [{OCO}Ir(MeCN) 3 ][PF 6 ] (4) or by reaction with either PMe 3 or PCy 3 to generate [{OCO}Ir(PMe 3 ) 3 ][PF 6 ] (5) or [{OCO}Ir(PCy 3 ) 2 (MeCN)][PF 6 ] (6), respectively. 6 reacts with CO in acetonitrile to give an equilibrium mixture of 6 and [{OCO}Ir(PCy 3 ) 2 (CO)][PF 6 ] (7) and with chloride to generate [{OCO}Ir(PCy 3 ) 2 Cl] . The solid-state structure of 8 shows that the diphenolate imidazolylcarbene ligand is distorted from planarity; DFT calculations suggest this is due to an antibonding interaction between the phenolates and the metal center in the highest occupied molecular orbital (HOMO) of the complex. 8 undergoes two successive reversible one-electron oxidations in CH 2 Cl 2 at -0.22 and at 0.58 V (vs ferrocene/ferrocenium); EPR spectra, mass spectroscopy, and DFT calculations suggest that the product of the first oxidation is [{OCO}Ir(PCy 3 ) 2 Cl] þ (8 þ ), with the unpaired electron occupying a molecular orbital that is delocalized over both the metal center and the diphenolate imidazolyl-carbene ligand.
Organometallics, 2010
Reactions between an N,N 0 -adamantyl-substituted bis(imidazolium) diiodide (CH imid CHCH imid )I 2 (1) and the dinuclear iridium(I) complex ([Ir( μ-X)(cod)] 2 [X = Cl, I (prepared in situ)] in the absence of a base yielded the hydrogen-bonded complexes [(CH imid CHCH imid )I] þ [IrCl(I)(cod)] -(2) and [(CH imid CHCH imid )I] þ [IrI 2 (cod)] -(2 0 ). The charge-assisted intermolecular C-H 3 3 3 X-M hydrogen-bonding interactions between the [(CH imid CHCH imid )I] þ cations and the [IrX(I)(cod)] -(X=Cl or I) anions involve two (C2-)H atoms of the imidazolium salt precursors and a halogen atom terminally bound to iridium. These hydrogen-bonded compounds can be converted to the monometalated iridium(I) N-heterocyclic carbene (NHC) complexes [IrCl(cod)(CH imid CHC NHC )]I (3) and [IrI(cod)(CH imid CHC NHC )]I (3 0 ) by strong or weak bases. On the basis of our experimental results, we suggest an explanation for the influence of the imidazolium counteranions on the metalation reactions. The reaction between the bis(imidazolium) diiodide and [Ir( μ-Cl)(cod)] 2 in the presence of excess Cs 2 CO 3 in refluxing acetonitrile directly afforded the monometalated iridium(I) NHC complex 3. The crystal structures of 2 0 3 MeCN and 3/3 0 3 MeCN have been determined by X-ray diffraction.
Journal of Molecular Structure 1211 (2020) 128058, 2020
A series of Iridium (III) complexes of general formula [Ir(ppy) 2 (L)] 0/þ (ppy ¼ 2-phenyl pyridine, L ¼ Schiff base) were synthesised from the dichloro bridged dimeric starting material, [(ppy) 2 Ir(m-Cl) 2 Ir(ppy) 2 ]. Three Schiff bases used as ligand were obtained from condensation of 2-amino phenol with benzalde-hyde (L1), salicylaldehyde with 2-aminopyridine (L2) and pyridine 2-aldehyde with 2-aminopyridine (L3). All the complexes were characterised by IR, 1 H NMR, electronic absorption spectroscopy and cyclic voltammetry studies. Molecular structure of two of these complexes were determined by single crystal X-ray structure analysis. Complexes displayed several weak absorptions in visible region in the range of 401e499 nm. TDDFT calculations on complexes revealed the ligand orbital dominance in both HOMO and LUMO orbitals and subsequent ligand centred transitions were observed in absorption spectra.
Preparation of Phosphorescent Iridium(III) Complexes with a Dianionic C,C,C,C-Tetradentate Ligand
Inorganic chemistry, 2018
The preparation and photophysical properties of heteroleptic iridium(III) complexes containing a dianionic C,C,C,C-tetradentate ligand and a cyclometalated phenylpyridine group are described. Complex [Ir(μ-OMe)(COD)](1, COD = 1,5-cyclooctadiene) reacts with 1,1-diphenyl-3,3-butylenediimidazolium iodide ([PhIm(CH)ImPh]I), in the presence NaOBu, to give [Ir(μ-I){κ- C, C, C, C-[CHIm(CH)ImCH]}](2), which leads to {[Ir{κ- C, C, C, C-[CHIm(CH)ImCH]}](μ-OH)(μ-OMe)} (3) by treatment first with silver trifluoromethanesulfonate (AgOTf) in acetone-dichloromethane and subsequently with KOH in methanol. The reaction of 2 with AgOTf and acetonitrile affords the bis(solvento) complex [Ir{κ- C, C, C, C-[CHIm(CH)ImCH]}(CHCN)]OTf (4). The latter promotes the pyridyl-supported heterolytic ortho-CH bond activation of the phenyl group of 2-phenylpyridine, 2-(2,4-difluorophenyl)pyridine, 2-( p-tolyl)pyridine, and 5-methyl-2-phenylpyridine to yield Ir{κ- C, C, C, C-[CHIm(CH)ImCH]}{κ- C, N-[Ar-py]} (Ar-py ...
Preparation and reactivity of iridium(III) hydride complexes with pyrazole and imidazole ligands
Journal of Organometallic Chemistry, 2006
Pyrazole IrHCl 2 (HRpz)P 2 [P = PPh 3 , P i Pr 3 ; R = H, 3-Me], bis(pyrazole) [IrHCl(HRpz) 2 (PPh 3 ) 2 ]BPh 4 and imidazole IrHCl 2 -(HIm)(PPh 3 ) 2 derivatives were prepared by allowing the IrHCl 2 (PPh 3 ) 3 complex to react with the appropriate azole in refluxing 1,2dichloroethane. Nitrile IrHCl 2 (CH 3 CN)(PPh 3 ) 2 and 2,2 0 -bipyridine (bpy) [IrHCl(bpy)(PPh 3 ) 2 ]BPh 4 derivatives were also prepared using IrHCl 2 (PPh 3 ) 3 as a precursor. The complexes were characterised spectroscopically (IR and NMR) and a geometry in solution was also established. Protonation with Brønsted acid of pyrazole IrHCl 2 (Hpz)(PPh 3 ) 2 and imidazole IrHCl 2 (HIm)(PPh 3 ) 2 complexes proceeded with the loss of the azole ligands and the formation of the unstable IrHCl 2 (PPh 3 ) 2 derivative. Vinyl IrCl 2 {CH@C(H)R1}(HRpz)P 2 and IrCl 2 {CH@C(H)R1}(HIm)P 2 (R1 = Ph, p-tolyl, COOCH 3 ; P = PPh 3 , P i Pr 3 ) complexes were prepared by allowing hydride-pyrazole IrHCl 2 (HRpz)P 2 and hydride-imidazole IrHCl 2 (HIm)P 2 to react with an excess of terminal alkyne in 1,2-dichloroethane. The complexes were characterised spectroscopically and by the X-ray crystal structure determination of the IrCl 2 {CH@C(H)Ph}(Hpz)(PPh 3 ) 2 derivative.