Novel binuclear doubly vinyl-bridged iridium complexes formed by olefinic C—H activation

Werner, Helmut; Wolf, Justin; Nessel, Angelika; Fries, Arno; Stempfle, Bernd; Nürnberg, Oliver

doi:10.1139/v95-130

Cited by 7 publications

(7 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The ruthenium(II) analogue [RuCp*(P–NH 2 )py]PF 6 was previously reported . We have also prepared the iridium(III) complex [IrCp(C–NH 2 )Cl]PF 6 ( 5 ), which contains a cyclopentadienyl ligand (Cp), by a transmetalation reaction , from 1 to [IrCpCl 2 ] 2 in refluxing acetonitrile for comparison purposes. The reaction between 1 and [IrCpBr 2 ] 2 did not result in the desired complex containing a bromide ligand.…”

Section: Resultsmentioning

confidence: 99%

“…We have also prepared the iridium(III) complex [IrCp(C–NH 2 )Cl]PF 6 ( 5 ), which contains a cyclopentadienyl ligand (Cp), by a transmetalation reaction , from 1 to [IrCpCl 2 ] 2 in refluxing acetonitrile for comparison purposes. The reaction between 1 and [IrCpBr 2 ] 2 did not result in the desired complex containing a bromide ligand. The Ir–C carbene resonance of 5 in acetonitrile- d 3 was observed at 149.0 ppm in its 13 C{ 1 H} NMR spectrum.…”

Section: Resultsmentioning

confidence: 99%

“…The synthesis of bis[1-(2-aminomethylphenyl)-3-methylimidazol-2-ylidene]nickel(II) hexafluorophosphate ( 1 ) has been reported previously . The syntheses of [IrCp*Cl 2 ] 2, [IrCpCl 2 ] 2 , 2-(diphenylphosphino)benzylamine (P–NH 2 ), and 1-( N,N- dimethylamino)propyl-3-methylimidazolium chloride hydrochloride (HC–NMe 2 ·HCl) were reported in the literature. All other reagents and solvents were purchased from commercial sources and were used as received.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Bifunctional Mechanism with Unconventional Intermediates for the Hydrogenation of Ketones Catalyzed by an Iridium(III) Complex Containing an N-Heterocyclic Carbene with a Primary Amine Donor

Lough

Morris

2012

Organometallics

View full text Add to dashboard Cite

An alcohol-assisted outer-sphere bifunctional mechanism for the H 2 hydrogenation of ketones catalyzed by an iridium system is presented on the basis of experimental and theoretical evidence. An iridium(III) complex containing an N-heterocyclic carbene (NHC) with a tethered primary amine donor (C−NH 2 ), [IrCp*(C−NH 2 )Cl]PF 6 (3; Cp* = pentamethylcyclopentadienyl ligand), when activated by an alkoxide base, catalyzed the H 2 hydrogenation of acetophenone and benzophenone under 25 bar of H 2 pressure at 50 °C, achieving a maximum turnover frequency (TOF) of 416 h −1 . The presence of 2-propanol accelerates catalysis only when the alkoxide base is used in large excess with respect to iridium. This system has activity for ketone hydrogenation that is inferior to that of the structurally similar ruthenium(II) complex [RuCp*(C−NH 2 )py]PF 6 (2; py = pyridine, TOF of up to 17 600 h −1 for the hydrogenation of acetophenone). On the other hand, an iridium(III) complex that contains a cyclopentadienyl ligand (Cp), [IrCp(C−NH 2 )Cl]PF 6 (5), has activity that is superior to that of its Cp* analogue (3) in the catalytic H 2 hydrogenation of acetophenone when activated by an alkoxide base, reaching a TOF of up to 687 h −1 . Consistent with our previous computational studies, an iridium(III) hydride−amine complex, [IrCp*(C−NH 2 )H]PF 6 (6), was isolated and was found to be inactive as a catalyst for ketone hydrogenation. The cationic charge is thought to contribute to a diminished hydricity and reactivity of the iridium(III) hydride in comparison to the neutral ruthenium(II) analogue. The important role of the N−H group is illustrated as well by the poor catalytic activity of the structurally similar iridium(III) complex [IrCp*(C−NMe 2 )Cl]PF 6 (8), which does not contain an N−H group. Nevertheless, we present evidence that complex 3, in the presence of an excess alkoxide base, does efficiently hydrogenate ketones via an outer-sphere bifunctional mechanism involving the novel, neutral hydride intermediate Ir(η 4 -Cp*H)(C−NH 2 )H. The formation of this intermediate relies on the uncommon migration of a hydride ligand to the η 5 -Cp* ligand which appears to be promoted by the unique NHC ligand of the present system.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Bifunctional Mechanism with Unconventional Intermediates for the Hydrogenation of Ketones Catalyzed by an Iridium(III) Complex Containing an N-Heterocyclic Carbene with a Primary Amine Donor

Lough

Morris

2012

Organometallics

View full text Add to dashboard Cite

show abstract

“…The short C1-C2 bond distance (1.429(6) Å) is intermediate between typical C-C single and C=C double bonds, in agreement with an unsaturated C 2 unit, and compares well with that found in related vinyl complexes. [64][65][66][67] The π-system of the vinyl anion is bound symmetrically to the iridium center: the Ir-C1 (2.128(4) Å) and Ir-C2 (2.1287(4) Å) distances are almost identical and lie well within the range for bond lengths between Ir and π-bonded carbons. 67,68 The Ta-C1 distance (2.141(4) Å) is in the expected range for a single bond, and is slightly shorter than the Ta-C neopentyl bond lengths (Ta1-C13 = 2.206(4) Å; Ta1-C16 = 2.232(4) Å).…”

Section: Scheme 5 Solvent-dependent Reactivity Of 2 Towards Neopentyl...mentioning

confidence: 87%

Reactivity of Tantalum/Iridium and Hafnium/Iridium Alkyl Hydrides with Alkyl Lithium Reagents: Nucleophilic Addition, Alpha-H Abstraction, or Hydride Deprotonation?

et al. 2022

View full text Add to dashboard Cite

Cp*IrH 4 reacts with Hf(Np) 4 (Np = CH 2 C(CH 3 ) 3 ) to yield the heterobimetallic complex [Hf(Np) 3 (μ-H) 3 IrCp*], 2. Treatment of 2 with neopentyl lithium (NpLi) results in the nucleophilic addition of a neopentyl moiety onto the Hf center, restoring Hf(Np) 4 and displacing the Cp*IrH 3 iridate fragment. By contrast, treatment of the tantalum/iridium analogue, [Ta(Np) 3 IrH 2 (Cp*)], 1, with NpLi triggers the α-hydrogen abstraction at a Ta-neopentyl moiety and leads to the formation of the alkylidene -ate complex [Li][{Ta(CH t Bu)(Np) 2 }{IrH 2 Cp*}], 4. The benzylidene analogue, [K][{Ta(CHPh)(Np) 2 }{IrH 2 Cp*}], 5, is obtained upon reacting 1 with benzyl potassium. An unusual vinyl oxo species, [{Li(THF) 3 }Ta(O)(Np) 2 {μ-C 2 H 3 }IrH(Cp*)], 6, is formed when the reaction of 1 with NpLi is carried out in THF, due to THF fragmentation.

show abstract

“…17 The vinyl ligand resulting from the ethylene oxidative addition bridges the metals in an asymmetric µ,η 1 :η 2 -coordination mode. 18 As a result of this coordination mode, the ligand distribution around the Ir(I) center resembles a trigonal bipyramid, with the two CdC moieties contained in the equatorial plane. Although such cis and coplanar arrangement of the two CdC fragments appears to be suitable for an insertion process, 3 did not evolve insertion products, even under harsh reaction conditions.…”

mentioning

confidence: 99%

Sequential C−H Activation and Dinuclear Insertion of Ethylene Promoted by a Diiridium Complex

et al. 2002

View full text Add to dashboard Cite

Novel binuclear doubly vinyl-bridged iridium complexes formed by olefinic C—H activation

Abstract: Treatment of [C,H,IrX,],, (2: X = C1; 3: X = Br) with CH,=CHtBu in the presence of Na,CO,-iPrOH gives, besides the bis(o1efin) complex [C5H,Ir(CH,=CHtBu)

Cited by 7 publications

References 25 publications

Bifunctional Mechanism with Unconventional Intermediates for the Hydrogenation of Ketones Catalyzed by an Iridium(III) Complex Containing an N-Heterocyclic Carbene with a Primary Amine Donor

Bifunctional Mechanism with Unconventional Intermediates for the Hydrogenation of Ketones Catalyzed by an Iridium(III) Complex Containing an N-Heterocyclic Carbene with a Primary Amine Donor

Reactivity of Tantalum/Iridium and Hafnium/Iridium Alkyl Hydrides with Alkyl Lithium Reagents: Nucleophilic Addition, Alpha-H Abstraction, or Hydride Deprotonation?

Sequential C−H Activation and Dinuclear Insertion of Ethylene Promoted by a Diiridium Complex

Contact Info

Product

Resources

About