Reduction–oxidation properties of organotransition-metal complexes. Part 32. One-electron oxidation of [Co(η4-cot)-(η-C5Me5)](cot = cyclooctatetraene): redox-induced polycyclic ring transformations of the resulting dimer, and crystal structure of [Co2(η4:η′4-C16H16)(η-C5Me5)2]

Aggarwal, Ranjana; Connelly, Neil G.; Dunne, Barry J.; Gilbert, M. M.; Orpen, A. Guy

doi:10.1039/dt9910000001

Cited by 10 publications

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References 26 publications

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confidence: 99%

“…There are literature precedents for the 1,2,5,6-η 2 ,η 2 binding mode of COT in iridium chemistry, for instance [IrCl(COT)] 2 and CpIr(COT), 74 although none has been structurally characterized to the best of our knowledge. Structures featuring this type of COT coordination are, however, available for Co I , 75 Mo 0 , 76 and Ru 0 . [77][78][79] Concerning the 1-κ-4,5,6-η 3 binding mode, as already mentioned above, this is documented for the homologous complex [IrH(1-κ-4,5,6-η-C 8 H 10 )(dppb)], 73 which was obtained by addition of dppb to [Ir(NH 2 )(COD)] 2 .…”

Section: Dalton Transactions Papermentioning

confidence: 99%

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Ir^I(η⁴-diene) precatalyst activation by strong bases: formation of an anionic Ir^III tetrahydride

et al. 2023

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Section: Resultsmentioning

confidence: 99%

Section: Dalton Transactions Papermentioning

confidence: 99%

Ir^I(η⁴-diene) precatalyst activation by strong bases: formation of an anionic Ir^III tetrahydride

et al. 2023

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Insights Into the Carbene‐Initiated Aggregation of [Fe(cot)₂]

et al. 2010

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In the last 20 years stable carbenes [1] In marked contrast, before our recent report,[9] organic species capable of mediating complicated stoichiometric and catalytic organometallic transformations were virtually nonexistent. We found that the interaction of the N,Nbis(2,4,6-trimethyl)phenyl substituted NHC (IMes) with bis(cyclooctatetraene)iron (Fe(COT) 2 ) produced the novel tetrametallic cluster 3, featuring two bound NHCs (Scheme 1, bottom right). When the N,N-bis(2,6-diisopropyl)phenyl substituted NHC (SIPr) interacted with Fe(COT) 2 , a carbene catalyzed process formed the unprecedented trimetallic cluster Fe 3 (COT) 3 4, (Scheme 1, bottom left), which is a hydrocarbon analogue of Dewar's classic Fe 3 (CO) 12 . [10] We postulated that the observed reactivity was due to the NHC's ability to induce a key M-M bond forming reaction, and we proposed that discrete mono 1 (LFeCOT) and bimetallic intermediates 2 (LFe 2 (COT) 2 ) were involved (Scheme 1, Top). We believe the outcomes of these reactions are different based on steric effects of the NHC initiators. The SIMes ligand remains bound to intermediate 2, and is not bulky enough to kinetically block the dimerization[11] process or the COT reduced form (Scheme 1, Top right). On the other

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Insights Into the Carbene‐Initiated Aggregation of [Fe(cot)₂]

et al. 2010

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In the last 20 years stable carbenes [1] have found numerous applications. They are excellent ancillary ligands for transition metal catalysts, [2] as exemplified by the state of the art ruthenium-based olefin metathesis catalysts.[3] Moreover, they coordinate main group elements in their zero oxidation state, [4] stabilize highly reactive species, [5] activate small molecules, [6] and act as efficient organocatalysts. [7] For the latter application, a myriad of other organocatalysts are known. [8] In marked contrast, before our recent report, [9] organic species capable of mediating complicated stoichiometric and catalytic organometallic transformations were virtually nonexistent. We found that the interaction of the N,N-bis(2,4,6-trimethyl)phenyl-substituted N-heterocyclic carbene (NHC) IMes with bis(cyclooctatetraene)iron ([Fe-(cot) [10]We postulated that the observed reactivity was due to the NHCs ability to induce a key M À M bond forming reaction, and we proposed that discrete monometallic intermediates 1were involved (Scheme 1, top). We believe the outcomes of these reactions are different based on steric effects of the NHC initiators. The SIMes ligand remains bound to intermediate 2, and is not bulky enough to kinetically block the dimerization [11] process or the cot-reduced form (Scheme 1, top right). On the other hand, the increased steric hindrance of the SIPr carbene, both protects the transient species 2 and also destabilizes the M À carbene bond to encourage the expulsion of [Fe 2 (cot) 2 ], which ultimately is incorporated into the [Fe 3 (cot) 3 ] triangle.Herein we report the reaction of [Fe(cot) 2 ] with three types of stable carbenes, namely an abnormal NHC (aNHC), a cyclic (alkyl)(amino)carbene (CAAC) and a carbocyclic carbene (BAC). Several hitherto unknown organometallic architectures have been isolated, including mono-and bimetallic iron complexes related to the plausible intermediates 1 and 2 along the carbene-catalyzed pathway to form [Fe 3 (cot) Initially reported by Crabtree et al. in 2001, [13] and then extensively utilized by Albrecht et al., [14] C-5 metal-bound imidazolylidenes or aNHCs are stronger donor ligands than their normal isomers. A possibly even more important characteristic of aNHCs is that they are believed to bind metals much stronger than classical NHCs. The recent isolation of a stable metal-free aNHC [15] has opened up the doorway to utilize such species as ligands for elements across the periodic table. We hypothesized that since this aNHC features intermediate steric hindrance between IMes and SIPr, and also is not known to act as a leaving group, it might be possible to strategically implement this ligand to stabilize the highly reactive [(L)Fe 2 (cot) 2 ] complex 2 (Scheme 1, top). Treatment of a pentane solution of [Fe(cot) 2 ] with half an equivalent of aNHC (Figure 1) leads to a blood-red solution,

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Cited by 10 publications

References 26 publications

Ir^I(η⁴-diene) precatalyst activation by strong bases: formation of an anionic Ir^III tetrahydride

Ir^I(η⁴-diene) precatalyst activation by strong bases: formation of an anionic Ir^III tetrahydride

Insights Into the Carbene‐Initiated Aggregation of [Fe(cot)₂]

Insights Into the Carbene‐Initiated Aggregation of [Fe(cot)₂]

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Reduction–oxidation properties of organotransition-metal complexes. Part 32. One-electron oxidation of [Co(η4-cot)-(η-C5Me5)](cot = cyclooctatetraene): redox-induced polycyclic ring transformations of the resulting dimer, and crystal structure of [Co2(η4:η′4-C16H16)(η-C5Me5)2]

Cited by 10 publications

References 26 publications

IrI(η4-diene) precatalyst activation by strong bases: formation of an anionic IrIII tetrahydride

IrI(η4-diene) precatalyst activation by strong bases: formation of an anionic IrIII tetrahydride

Insights Into the Carbene‐Initiated Aggregation of [Fe(cot)2]

Insights Into the Carbene‐Initiated Aggregation of [Fe(cot)2]

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Ir^I(η⁴-diene) precatalyst activation by strong bases: formation of an anionic Ir^III tetrahydride

Ir^I(η⁴-diene) precatalyst activation by strong bases: formation of an anionic Ir^III tetrahydride

Insights Into the Carbene‐Initiated Aggregation of [Fe(cot)₂]

Insights Into the Carbene‐Initiated Aggregation of [Fe(cot)₂]