From an <i>N</i>‐Methyl N‐Heterocyclic Carbene to Carbyne and Carbide Ligands via Multiple CH and CN Bond Activations

Cabeza, Javier A.; Rı́o, Ignacio del; Miguel, Daniel; Sánchez-Vega, M. Gabriela

doi:10.1002/ange.200705154

Cited by 15 publications

(8 citation statements)

References 46 publications

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“…similar to that of 2. The Os−C(1) bond lengths of 2.022 (4) and 2.029(4) Å compare well with the distances reported for other Os−imidazolylidene derivatives with normal coordination of the NHC. 20 The 1 H, 13 C{ 1 H}, and 31 P{ 1 H} NMR spectra of 3, in benzene-d 6 at room temperature, are consistent with the structure shown in Figure 3.…”

Section: ■ Results and Discussionsupporting

confidence: 80%

“…1 H NMR (400 MHz, C 6 D 6 , 298 K): δ 7.53 (br, 2H, CH Ph ), 7.27 (dd, 3 J H−H = 7.6, 3 J H−H = 7.6, 2H, CH Ph ), 6.85 (t, 3 J H−H = 7.6, 1H, CH Ph ), 6.10 (s, 1H, CH imidazole ), 5.97 (s, 1H, CH imidazole ), 3.99 (s, 3H, NCH 3 ), 3.43 (s, 2H, NCH 2 ), 2.96 (br, 1 H, CHPh) 2.74−2.62 (m, 6H, PCH), 1.23 (dvt, 3 J H−H= 6.4, N = 12.8, 18H, PCH(CH 3 ) 2 ), 1.18 (dvt, 3 J H−H = 6.4, N = 12.8, 18H, PCH(CH 3 )2 ). 13 C{ 1 H}-APT NMR plus HSQC and HMBC (75.5 MHz, C 6 D 6 , 298 K): δ 308.6 (t, 2 J C−P = 12.8, OsCC), 233.7 (t, 2 J C−P = 6.8, CO), 180.0 (t, 2 J C−P = 7.6, NCN), 131.1 (t,4 J C−P = 2.3, C ipso ), 128.2 (s, CH Ph ), 126.7 (s, CH Ph ), 125.4 (s, CH imidazole ), 123.5 (s, CH Ph ), 117.0 (t, 3 J C−P = 3.8, CHPh), 116.9 (s, CH imidazole ), 74.4 (s, CH 2 ), 37.1 (s, NCH 3 ), 26.1 (vt, N = 23.4, PCH), 20.3 and 20.0 (both s, PCH(CH 3 ) 2 ). 31 P{ 1 H} NMR (162.0 MHz, C 6 D 6 , 298 K): δ −11.7 (s).…”

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confidence: 99%

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Conceptual Extension of the Degradation–Transformation of N-Heterocyclic Carbenes: Unusual Rearrangements on Osmium

2018

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The range of processes of degradation−transformation of NHC ligands in the coordination sphere of a transition metal has been enlarged. The NHC-acyl ligand of the complex Os{κ 2-C,C-[C(O)CH 2 ImMe]}Cl(P i Pr 3) 2 (1) undergoes a complex rearrangement promoted by internal alkynes to give Os{κ 2-C,N-[CH 2 ImMe]}Cl(CO)(P i Pr 3) 2 (2). Mechanistic studies have revealed that the degradation involves a catalytic alkyne-mediated deinsertion of CO from the acyl moiety to afford Os{κ 2-C,C-[CH 2 ImMe]}Cl(CO)(P i Pr 3) 2 (3), followed by a thermally activated stoichiometric 1,2-methylene shift from N to C. The catalytic activity of the alkynes depends upon their substituents, decreasing in the sequence diphenylacetylene > 1-phenyl-1-propyne > 3-hexyne > 2-butyne. Phenylacetylene tautomerizes in the metal coordination sphere to afford the stable vinylidene Os{κ 2-C,C-[C(O)CH 2 ImMe]}Cl(CCHPh)(P i Pr 3) 2 (4), which experiences the coupling of the acyl moiety and the vinylidene ligand under a carbon monoxide atmosphere. The addition of HBF 4 •OEt 2 to the resulting complex Os{κ 2-C,C-[C(CHPh)C(O)CH 2 ImMe]}Cl-(CO) 2 (P i Pr 3) (5) leads to [Os{κ 2-O,C-[OC(CHCHPh)CH 2 ImMe]}Cl(CO) 2 (P i Pr 3)]BF 4 (6) containing an NHC-(α,βunsaturated ketone) ligand.

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Section: ■ Results and Discussionsupporting

confidence: 80%

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confidence: 99%

Conceptual Extension of the Degradation–Transformation of N-Heterocyclic Carbenes: Unusual Rearrangements on Osmium

2018

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“…8 Recent model studies focus on CN double‐bond cleavage of aromatic N‐heterocycles, because this process presents the promising opportunity of eliminating an expensive and energy intensive hydrogenation step 9. Ultimately, an aliphatic CN bond scission must occur, and herein we provide a relevant example of a unique CN bond activation across a WW dimer and the formation of a bridging methylidyne ligand by methyl dehydrogenation 10. This sequence of reactions represents a model pathway for site deactivation of commercial HDN catalysts.…”

Section: Methodsmentioning

confidence: 89%

Primary Carbon–Nitrogen Bond Scission and Methyl Dehydrogenation across a WW Multiple Bond

et al. 2010

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“…Recent studies by our group [17] and also by those of Whittlesey [16] and Cole [18] have revealed that some imidazolederived NHCs can be incorporated into triruthenium carbonyl clusters, when the NHCs are not used in excess, [16c, 18] to give isolable derivatives of the type [Ru 3 (CO) 11 (NHC)]. These clusters are prone to undergo intramolecular C(sp 2 )ÀH, [16a,b] C(sp 3 )ÀH, [17a,c-e] and/or C(sp 2 )ÀN [17d] bond-activation processes, but only the double CÀH activation of a methyl group in [Ru 3 (CO) 11 (Me 2 Im)] (Me 2 Im = 1,3-dimethylimidazol-2-ylidene) has been mechanistically studied.…”

Section: In Memory Of Lorenzo Pueyomentioning

confidence: 98%

A Simple Preparation of Pyridine‐Derived N‐Heterocyclic Carbenes and Their Transformation into Bridging Ligands by Orthometalation

et al. 2008

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A plethora of transition-metal complexes containing Nheterocyclic carbene (NHC) ligands have been prepared over the past decade, [1] particularly because many of them are among the most active catalysts for important organic reactions, such as olefin metathesis and various C À C bondforming processes. [2] The great majority of the NHC ligands of these complexes are two-nitrogen, five-membered, heterocyclic carbenes.Metal complexes containing one-nitrogen, six-membered, heterocyclic carbene ligands are far less common. [3][4][5][6][7][8][9][10][11][12] Cationic nickel(II) or palladium(II) complexes that have been prepared in the laboratories of Raubenheimer, Herrmann, or Frenking by oxidative addition (or oxidative substitution) of the CÀX (X = halogen) bond of N-alkyl (or N-aryl) halopyridinium (or haloquinolinium, haloacridinium, etc.) salts to appropriate metal(0) precursors. [3] This synthetic method is restricted to metal complexes that can undergo easy oxidative addition reactions. It can provide not only complexes with normal pyrid-2-ylidene-type ligands, in which the metal is bound to a C atom away from the N atom of the heterocyclic ligand (A in Scheme 1, for example), but also complexes with remote pyrid-4-ylidene-type ligands, in which the metal is bound to a C atom para to the N atom (B in Scheme 1, for example). These complexes are also active as catalysts for C À C coupling reactions. [3,5] Some pyridine-derived NHC ligands have also been prepared by oxidative addition of pyridinium CÀH bonds, [6] N-alkylation of coordinated pyridyl ligands, [7] and deprotonation of isoquinolinium cations. [8] Recent studies by the groups of Bergman, [9] Carmona, [10] Esteruelas, [11] and Li [12] have shown that some pyridines can undergo metal-induced rearrangements to form NHC ligands. These reactions, which are restricted to a few metal systems, generally involve tautomerization processes (such as that shown in Scheme 2 for 2-substituted pyridines).Herein, we report that simple pyrid-2-ylidenes can also be prepared by deprotonation of N-substituted pyridinium cations (Scheme 3) and that they can be trapped in solution by metal complexes, such as [Ru 3 (CO) 12 ]. Interestingly, the great basicity of this type of NHC [3,6] and the polynuclear character of the ruthenium cluster trigger the room-temperature transformation of the initial k 1 -C 2 -pyrid-2-ylidene ligands into unprecedented face-capping m 3 -k 2 -C 2 ,C 3 -pyrid-3yl-2-ylidene ligands by orthometalation. The mechanism of this process, modeled by density functional (DFT) calculations, is also reported.Scheme 2. Metal-induced tautomerization of substituted pyridines.Scheme 3. Deprotonation of N-methylpyridinium to give N-methylpyrid-2-ylidene. The carbene (C) and ylidic (D and E) resonance structures of this NHC are also shown. Scheme 1. Syntheses of complexes containing "normal" (A) and "remote" (B) pyridylidene ligands derived from halopyridinium cations.

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From an N‐Methyl N‐Heterocyclic Carbene to Carbyne and Carbide Ligands via Multiple CH and CN Bond Activations

Cited by 15 publications

References 46 publications

Conceptual Extension of the Degradation–Transformation of N-Heterocyclic Carbenes: Unusual Rearrangements on Osmium

Conceptual Extension of the Degradation–Transformation of N-Heterocyclic Carbenes: Unusual Rearrangements on Osmium

Primary Carbon–Nitrogen Bond Scission and Methyl Dehydrogenation across a WW Multiple Bond

A Simple Preparation of Pyridine‐Derived N‐Heterocyclic Carbenes and Their Transformation into Bridging Ligands by Orthometalation

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