Synthesis of PdII Complexes Bearing pNHC Ligands by Oxidative Addition of 8-Halogenotheophyllines and 8-Bromoadenine to Pd0

Blumenberg, Jonas; Wilm, Lukas F. B.; Hahn, F. Ekkehardt

doi:10.1021/acs.organomet.0c00046

Cited by 14 publications

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“…Comparing its structure with that of [(IMes)Co(η 2 :η 2 -dvtms)] revealed that the reduction reaction has resulted in the conversion of the IMes ligand into a N -mesityl imidazolate ligand with K(18-crown-6) coordinating on the N 3 position. Similar imidazolate complexes without a cation coordinated by the unsubstituted ring nitrogen atom have been obtained by the oxidative addition of neutral 2-halogenoazoles to suitable (low-valent) transition-metal complexes. − The K–N distance (2.727(3) Å) is typical of the ionic K–N bond of potassium N -imidazolate compounds . The N -mesityl imidazolate ligand has C1–N1 and C1–N2 distances of 1.348(3) and 1.388(4) Å, respectively, and C1–N1–C6 and C1–N2–C7 angles of 110.0(2)°.…”

Section: Results and Discussionsupporting

confidence: 74%

Cobalt(−I)- and Rhodium(−I)-Mediated Dearylation of N-Aryl N-Heterocyclic Carbene Ligands

et al. 2020

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N-heterocyclic carbene (NHC) ligands are intensively used in transition-metal-catalyzed reactions. Their bond-activation reactions, however, are much less understood. We now report unprecedented dearylation reactions of N-aryl-substituted NHCs mediated by cobalt(−I) and rhodium(−I) species, which lead to the conversion of N-aryl NHCs into N-aryl imidazolate ligands. The reduction reactions of [(IMes)Co(η2:η2-dvtms)] (IMes = 1,3-dimesitylimidazol-2-ylidene, dvtms = divinyltetramethyldisiloxane) and [Rh(cod)Cl]2/IPr (cod = cycloocta-1,5-diene, IPr = 1,3-bis(2′,6′-diisopropylphenyl)imidazol-2-ylidene) with KC8 and 18-crown-6 gave the corresponding N-aryl imidazolate complexes [(18-crown-6)K(μ-C3H2N2Mes-κC 2,κN 3)Co(η2:η2-dvtms)] (1) and [K(18-crown-6)(THF)][(η2 :η 2-cod)2Rh2(μ-C3H2N2(Dipp)-κC 2,κN 3)2(μ-Dipp)2K] (3), which have been characterized by NMR and X-ray diffraction studies. In supporting the possible involvement of cobalt(−I) and rhodium(−I) species in the dearylation reactions, the three-coordinate formal cobalt(−I) and rhodium(−I) complexes [K(2,2,2-Crypt)][(ICy)Co(η2:η2-dvtms)] (2) and [K(18-crown-6)][(IPr)Rh(η2:η2-dvtms)] (5) have been obtained from the reduction reactions of [(ICy)Co(η2:η2-dvtms)] (ICy = 1,3-dicyclohexylimidazol-2-ylidene) and [Rh(dvtms)Cl]2/IPr with KC8 and crown ethers. These results suggest that the C–N bond cleavage step of the dearylation reactions is likely achieved by cobalt(−I)-/rhodium(−I)-mediated C–N bond oxidative addition and also imply the possible involvement of similar degradation reactions in N-aryl NHC-transition-metal-catalyzed reactions operating under strong reducing conditions.

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Section: Results and Discussionsupporting

confidence: 74%

Cobalt(−I)- and Rhodium(−I)-Mediated Dearylation of N-Aryl N-Heterocyclic Carbene Ligands

et al. 2020

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“…Complexes [ 1 ]–[ 4 ] constitute additional examples for the preferred oxidative addition of 8-halogenotheophyllines to transition metals proceeding under the reaction of the N7–H bond while the C8–halogen bond remains intact. Previously, we reported the N7–H oxidative addition in the reaction of 8-halogenotheophyllines with [Ni(cod) 2 ]/PEt 3 (Scheme , middle) and the C8–halogen oxidative addition in the same reaction with [Pd(PPh 3 ) 4 ] (Scheme , bottom) . These reactions are most likely thermodynamically controlled .…”

Section: Resultsmentioning

confidence: 88%

“…Previously, we reported the N7–H oxidative addition in the reaction of 8-halogenotheophyllines with [Ni(cod) 2 ]/PEt 3 ( Scheme 1 , middle) 10 and the C8–halogen oxidative addition in the same reaction with [Pd(PPh 3 ) 4 ] ( Scheme 1 , bottom). 11 These reactions are most likely thermodynamically controlled. 10 The factors determining the outcome of the reaction of 8-halogenotheophyllines with Ir I complexes are not yet clear, but it appears that the formation of the N7^O1 chelate rings favors the N7–H oxidative addition over the reaction at the C8–X bond.…”

Section: Resultsmentioning

confidence: 99%

“…This unusual N-metalation of halogenoazole derivatives was only observed in the oxidative addition to Ni 0 at low temperature. If [Pd(PPh 3 ) 4 ] instead of Ni 0 was used as a metal precursor, the oxidative addition of 8-halogenotheophyllines yielded the expected complexes of type III with a C-metalated azolato ligand, which upon addition of a proton acid react to give the complexes with the diprotic, unsymmetric NH, NH–NHC ligands IV …”

Section: Introductionmentioning

confidence: 99%

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Synthesis of Ir^III Hydrido Complexes by Oxidative Addition of Halogenated Theophylline and Adenine Derivatives

et al. 2020

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The Ir III hydrido complexes [ 1 ] and [ 2 ] have been synthesized by the regioselective oxidative addition of the N7–H bond of 8-halogenotheophyllines to [IrCl(coe) 2 ] 2 in the presence of PPh 3 . The use of dppf in this reaction yielded the bimetallic Ir III /Fe II hydrido complexes [ 3 ] and [ 4 ]. X-ray diffraction studies confirmed that complexes [ 1 ]–[ 4 ] feature a theophyllinato ligand coordinated to the metal center in the rarely observed, chelating fashion via the N7 and O1 atoms. In addition, 8-bromoadenine reacts with [IrCl(coe) 2 ] 2 in the presence of PPh 3 to form the Ir III hydrido complex [ 5 ] which features one anionic 8-bromoadeninato and one neutral 8-bromoadenine ligand linked by an intramolecular hydrogen bond. Complex [ 5 ] was characterized by high-resolution mass spectrometry and an X-ray diffraction analysis but could not be analyzed by nuclear magnetic resonance spectroscopy because of its low solubility.

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“…The resulting diaminoheterocycles in [ 13a ] and [ 15a ] carry a negative charge at one of the ring nitrogen atoms. While these complexes have not been isolated, related azolato complexes have been observed multiple times. , The negatively charged ring nitrogen atom then attacked the C–F bond of a neighboring o -fluorophenyl group to give complexes [ 13b ] + and [ 15b ] + , respectively. This reaction is normally observed upon deprotonation of NH,NH-NHC ligands in the template-controlled preparation of [11]ane-P 2 C NHC macrocycles (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Ruthenium(II) Complexes Bearing Macrocyclic [11]ane-P₂C^NHC Ligands by a Template-Controlled Domino Reaction

et al. 2021

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Coordination of 1,2-dis[bis(o-fluorophenyl)phosphino]ethane (1) and a β-functionalized isocyanide (2-azidoethyl isocyanide (3) or 2-nitrophenyl isocyanide (6)) in a facial manner to the{Ru(indenyl)}+ template followed by reduction of the isocyanides yielded the NH,NH-NHC complex [5][ZnCl4]0.5 for isocyanide 3 and the 2-aminophenyl isocyanide complex [8]Cl for isocyanide 6, respectively. Deprotonation of the ring nitrogen atoms in [5][ZnCl4]0.5 gave, via an intramolecular nucleophilic substitution, complex [9][ZnCl4]0.5 bearing a facially coordinated [11]ane-P2CNHC ligand. Attempts to remove the η5-indenyl ligand led to decomposition of [9][ZnCl4]0.5. Repetition of the template synthesis at the {Ru(η5-2,4-dimethylpentadienyl)}+ template initially yielded complexes [13] and [15]BF4, both bearing a 2-amine-substituted isocyanide. Cyclization of the isocyanides in [13] and [15]BF4 to the NH,NH-NHCs was achieved by amine deprotonation with KOtBu. This led not only to the formation of the NHC ligand but also subsequently in a domino reaction to the formation of [11]ane-P2CNHC macrocycles in complexes [16]BF4 and [17]BF4. The η5-pentadienyl ligand in [16]BF4 and [17]BF4 was substituted for a chlorido and two acetonitrile ligands to give the ruthenium(II) complexes [18]BF4 and [19]BF4.

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Synthesis of Pd^II Complexes Bearing pNHC Ligands by Oxidative Addition of 8-Halogenotheophyllines and 8-Bromoadenine to Pd⁰

Cited by 14 publications

References 39 publications

Cobalt(−I)- and Rhodium(−I)-Mediated Dearylation of N-Aryl N-Heterocyclic Carbene Ligands

Cobalt(−I)- and Rhodium(−I)-Mediated Dearylation of N-Aryl N-Heterocyclic Carbene Ligands

Synthesis of Ir^III Hydrido Complexes by Oxidative Addition of Halogenated Theophylline and Adenine Derivatives

Synthesis of Ruthenium(II) Complexes Bearing Macrocyclic [11]ane-P₂C^NHC Ligands by a Template-Controlled Domino Reaction

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Synthesis of PdII Complexes Bearing pNHC Ligands by Oxidative Addition of 8-Halogenotheophyllines and 8-Bromoadenine to Pd0

Cited by 14 publications

References 39 publications

Cobalt(−I)- and Rhodium(−I)-Mediated Dearylation of N-Aryl N-Heterocyclic Carbene Ligands

Cobalt(−I)- and Rhodium(−I)-Mediated Dearylation of N-Aryl N-Heterocyclic Carbene Ligands

Synthesis of IrIII Hydrido Complexes by Oxidative Addition of Halogenated Theophylline and Adenine Derivatives

Synthesis of Ruthenium(II) Complexes Bearing Macrocyclic [11]ane-P2CNHC Ligands by a Template-Controlled Domino Reaction

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Synthesis of Pd^II Complexes Bearing pNHC Ligands by Oxidative Addition of 8-Halogenotheophyllines and 8-Bromoadenine to Pd⁰

Synthesis of Ir^III Hydrido Complexes by Oxidative Addition of Halogenated Theophylline and Adenine Derivatives

Synthesis of Ruthenium(II) Complexes Bearing Macrocyclic [11]ane-P₂C^NHC Ligands by a Template-Controlled Domino Reaction