Iridaoxacyclohexadiene-Bridged Mixed-Valence Iridium Cyclooctadiene Complex: Oxidative Addition and Hydrogen-Transfer to Coordinated Cyclooctadiene

Abstract

The systematic exploration of the synthesis of heteropentadienyl metal complexes leads us to study the metathesis reaction of [(η 4 -COD)Ir(μ 2 -Cl)] 2 with lithium 2,4-dimethyloxopentadienide, which affords the dinuclear Ir 0 −Ir II compound (η 4 -COD)Ir[η 1:1 -μ 2 -η 4 -CHC(Me)CHC(Me)O)]-Ir(η 4 -COD) (1) with a metal−metal bond. The COD ligands are coordinated η 4 to each Ir center, whereas the oxopentadienyl ligand is bridging both Ir atoms, allowing the formation of a novel iridapyran complex with Ir II and bonding η 4 with Ir 0

Pyridyl-Directed C–H and C–Br Bond Activations Promoted by Dimer Iridium-Olefin Complexes

“…The other oxygen atom of the O,O-chelate acac ligand lies trans to the metalated phenyl group (O(2)–Ir–C(9) = 160.62(8)°), whereas the pyridyl ring is situated trans to the C(5)–C(6) double bond (N–Ir–M(2) = 173.33(8)°). The functionalized carbocycle coordinates with three different Ir–C bond lengths of 2.074(2) (Ir–C(2)) Å, 2.172(2) (Ir–C(5)) Å, and 2.169(2) (Ir–C(6)) Å, which agree with those reported for compounds bearing C 8 H 12 R rings similarly linked to iridium­(III) . The length of the coordinated C(5)–C(6) bond of 1.391(3) Å also compares well with the lengths of C(1)–C(2) and C(5)–C(6) in 9 .…”

“…This suggests that the addition to C(1)–C(2) takes place outside to the metal. The 1 H and 13 C­{ 1 H} NMR spectra of 10 , in dichloromethane- d 2 , at room temperature are consistent with the structure shown in Figure and the spectra of related compounds. , In the 1 H NMR spectrum, the most noticeable features are the two olefinic resonances at 5.05 and 4.58 ppm and the signal due to the IrC­(sp 3 )H hydrogen atom, which appears at 1.28 ppm. In the 13 C­{ 1 H} NMR spectrum, the resonances corresponding to the C­(sp 2 ) atoms C(5) and C(6) are observed at 82.8 and 77.4 ppm, whereas the signal due to C(2) appears at 10.5 ppm.…”

Protic NHC Iridium Complexes with β-H Reactivity–Synthesis, Acetonitrile Insertion, and Oxidative Self-Activation

“…Complex 9 has a unique C s symmetry with two anionic NHC ligands and a hydride bridging its iridium atoms (δ­( 1 H) −20.01 ppm) . While bimetallic iridium species with bridging hydride ligands are well-known, ,− those with bridging NHC ligands are rare and tend to have them coordinated in a head-to-tail fashion between identical metal centers. − In contrast, 9 features a head-to-head arrangement with inequivalent Ir centers. This is supported by two distinct Cp*-CH 3 1 H and 13 C NMR chemical shifts (δ­( 1 H) 2.23, 2.15; δ­( 13 C) 11.8, 10.9 ppm).…”

“…The intriguing bonding in the metallic core of 9 , with its bridging hydride and delocalized anionicity of the NHC ligands, makes the oxidation states of the metal centers ambiguous (i.e., Ir­(III)Ir­(III), Ir­(II)Ir­(IV), or Ir­(II)→Ir­(IV)). Intermetallic interaction between the two Ir centers seems arguable − because of the rather large separation (Ir11Ir21 = 3.0410(4), Ir12Ir22 = 3.0501(4) Å).…”

“…The intriguing bonding in the metallic core of 9 , with its bridging hydride and delocalized anionicity of the NHC ligands, makes the oxidation states of the metal centers ambiguous (i.e., Ir­(III)Ir­(III), Ir­(II)Ir­(IV), or Ir­(II)→Ir­(IV)). Intermetallic interaction between the two Ir centers seems arguable − because of the rather large separation (Ir11Ir21 = 3.0410(4), Ir12Ir22 = 3.0501(4) Å). Since the low solubility of 9 prevented CV measurements, we used a QTAIM analysis on a BP86-D3­(ZORA)/TZ2P , optimized geometry, which showed near-identical bond paths of the two iridium nuclei to the hydride (critical bond points Ir11–H1 ρ 0.12 au, ε 0.09, Ir21–H1 ρ 0.10 au, ε 0.08; ring critical points Ir11–H1–Ir21–N31–C81: ρ 0.03 au, Ir11–H1–Ir21–N11–C11: ρ 0.03 au) but no intermetallic interactions (Figure and Figure S36 in the Supporting Information).…”