Synthesis, characterization and reactivity of iridium pincer complexes

Shafiei‐Haghighi, Sara; Singer, Laci M.; Tamang, Sem Raj; Findlater, Michael

doi:10.1016/j.poly.2017.09.005

Cited by 7 publications

(9 citation statements)

References 42 publications

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“…Moreover, the C–Ir–P angle of 79° and N–Ir–P angles of 100° and 101° for complexes 2 and 3 , respectively, are consistent with a distorted square-planar geometry around the iridium center. This unsymmetrical binding motif and ligand distortion are consistent with previously published metal–pincer complexes. ,, …”

Section: Resultssupporting

confidence: 92%

“…Based upon the NMR spectroscopic data for complexes 2 – 4 , the coordination environment around the iridium center is consistent with pseudo-square-planar geometry with time-averaged C 2 v symmetry . The associative mechanism is considered to be more common in 16 e , d 8 square-planar complexes and is more likely to occur for electron-deficient metal centers; this mechanism therefore avoids formation of electron-deficient 14 e species .…”

Section: Resultsmentioning

confidence: 95%

“…This unsymmetrical binding motif and ligand distortion are consistent with previously published metal−pincer complexes. 1,25,26 Ligand-Exchange Studies by NMR and UV−Vis Spectroscopy. Previously, 25 we demonstrated that addition of CO or C 2 H 4 to 4 resulted in the formation of the known complexes ( tBu POCOP)Ir(CO) (5) 27 and ( tBu POCOP)Ir-(C 2 H 4 ) (6) 28 at room temperature and 75 °C, respectively, and 1 equiv of free PPh 3 .…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Subsequently, (0.0479 mmol) of ligand (acetonitrile or pyridine) was added, resulting in an instantaneous color change of the reaction mixture from red to bright brown. The solution was filtered by using a syringe filter, and the volatiles were removed in vacuo to yield a light yellow solid product …”

Section: Methodsmentioning

confidence: 99%

“…24 Surprisingly, given their popularity in organometallic chemistry, to the best of our knowledge there is still a lack of comparable ligand exchange studies employing iridium− pincer complexes. 21 Previously, we have reported the synthesis of ( tBu POCOP)Ir(L) (L = MeCN (2), pyridine (3)) complexes (Scheme 1 and Figure 1), 25 which we viewed as excellent test beds for such fundamental ligand exchange studies. Herein, we report on our experimental and computational studies of ligand exchange chemistry between ( tBu POCOP)Ir(PPh 3 ) (4) and exogenous ligand, L (L = MeCN, pyridine).…”

Section: ■ Introductionmentioning

confidence: 99%

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Experimental and Computational Studies of Phosphine Ligand Displacement in Iridium–Pincer Complexes Employing Pyridine or Acetonitrile

et al. 2020

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This report describes the synthesis, characterization, and ligand exchange studies of iridium-based, pincer complexes. ( t B u POCOP)Ir(PP h 3 ) ( t B u POCOP = 2,6-bis(di-tertbutylphosphonito)benzene) serves as a convenient source of the latent Ir(I), 14-electron species [( tBu POCOP)Ir] and is susceptible to ligand exchange chemistry; reactions with acetonitrile and pyridine afford the corresponding ( tBu POCOP)Ir(NCMe) (2) and ( tBu POCOP)Ir(Py) (3) complexes, respectively. Varying concentrations of both pyridine and acetonitrile, the kinetic and thermodynamic parameters of the ligand exchange process between ( tBu POCOP)Ir(PPh 3 ) and L (L = MeCN or pyridine) were determined by employing NMR, UV−vis spectroscopy, and density functional theory (DFT) calculations to measure the relevant equilibria. A discussion of these results allows us to address whether phosphine displacement occurs via an associative or a dissociative pathway.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 95%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Experimental and Computational Studies of Phosphine Ligand Displacement in Iridium–Pincer Complexes Employing Pyridine or Acetonitrile

et al. 2020

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Effect of Ligands on the Lewis Acidity of the Metal and the Binding of N‐Bases to Iridium Pincer Complexes

et al. 2019

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The coordination of pyridine (Py) and benzonitrile (PhCN) to benzene based pincer hydridochlorides [(PCP)IrH(Cl)] (1), [(POCOP)IrH(Cl)] (2), [{EtO(O)C‐POCOP}IrH(Cl)] (3), and [(PCN)IrH(Cl)] (4) was studied spectroscopically and computationally to deduce the ligand influence. The variable temperature NMR (1H, 31P, 15N) and UV/Visible spectroscopic measurements revealed preferential coordination of these N‐donor ligands in the apical position of 1–4 and gave the formation enthalpies for the hexacoordinate complexes, which follow the order: 1 ≈ 4 > 3 > 2. This order nicely agrees with the order of Lewis acidity obtained for these complexes in DFT calculations. The orbital and electron density distribution analysis were performed at the DFT/M06 theory level for 1–4 and a series of p‐substituted PCP‐based hydridochlorides. The increasing Lewis acidity of iridium [as a maximum energy, VS,max, of molecular electrostatic potential (MEP)] correlates with decreasing basicity of Cl‐ligand (as MEP minimum, VS,min) as well as with Hammett σp parameters of p‐substituents. Importantly, these properties are conserved upon conversion into the corresponding dihydrides, as shown on the example of 1 and 4.

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