Recent advances in the chemistry of group 9—Pincer organometallics

Martı́n, Marta; Sola, Eduardo

doi:10.1016/bs.adomc.2019.09.002

Cited by 9 publications

(2 citation statements)

References 671 publications

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“…Pincer-type metal complexes are an indispensable class of catalytic materials for a variety of chemical transformations. A plethora of pincer-type ligand-based transition-metal complexes have been used as catalysts for the hydrogenation of various functional groups. − One of the notable pincer-type complexes is the commercially available Ru-Macho complex, which is a highly robust catalyst for several transformations, including the reduction of carbon dioxide, ester, and carbonyl compounds, as well as the dehydrogenation of amines, alcohols, and formic acid. ,− …”

Section: Introductionmentioning

confidence: 99%

Direct Heterogenization of the Ru-Macho Catalyst for the Chemoselective Hydrogenation of α,β-Unsaturated Carbonyl Compounds

2021

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In this study, a commercially available homogeneous pincer-type complex, Ru-Macho, was directly heterogenized via the Lewis acid-catalyzed Friedel–Crafts reaction using dichloromethane as the cross-linker to obtain a heterogeneous, pincer-type Ru porous organometallic polymer (Ru-Macho-POMP) with a high surface area. Notably, Ru-Macho-POMP was demonstrated to be an efficient heterogeneous catalyst for the chemoselective hydrogenation of α,β-unsaturated carbonyl compounds to their corresponding allylic alcohols using cinnamaldehyde as a model compound. The Ru-Macho-POMP catalyst showed a high turnover frequency (TOF = 920 h–1) and a high turnover number (TON = 2750), with high chemoselectivity (99%) and recyclability during the selective hydrogenation of α,β-unsaturated carbonyl compounds.

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Section: Introductionmentioning

confidence: 99%

Direct Heterogenization of the Ru-Macho Catalyst for the Chemoselective Hydrogenation of α,β-Unsaturated Carbonyl Compounds

2021

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“…Pincer ligands have risen to prominence in coordination chemistry and organometallics, in the last two decades, 1 due to the performance of complexes bearing this class of groups in catalysis 2 and materials science, 3 among other fields. 4 Several reasons could be mentioned to explain this fact.…”

Section: Introductionmentioning

confidence: 99%

Competition between N,C,N-Pincer and N,N-Chelate Ligands in Platinum(II)

et al. 2023

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Replacement of the chloride ligand of PtCl{κ3-N,C,N-[py-C6HR2-py]} (R = H (1), Me (2)) and PtCl{κ3-N,C,N-[py-O-C6H3-O-py]} (3) by hydroxido gives Pt(OH){κ3-N,C,N-[py-C6HR2-py]} (R = H (4), Me (5)) and Pt(OH){κ3-N,C,N-[py-O-C6H3-O-py]} (6). These compounds promote deprotonation of 3-(2-pyridyl)pyrazole, 3-(2-pyridyl)-5-methylpyrazole, 3-(2-pyridyl)-5-trifluoromethylpyrazole, and 2-(2-pyridyl)-3,5-bis(trifluoromethyl)pyrrole. The coordination of the anions generates square-planar derivatives, which in solution exist as a unique species or equilibria between isomers. Reactions of 4 and 5 with 3-(2-pyridyl)pyrazole and 3-(2-pyridyl)-5-methylpyrazole provide Pt{κ3-N,C,N-[py-C6HR2-py]}{κ1-N 1-[R′pz-py]} (R = H; R′ = H (7), Me (8). R = Me; R′ = H (9), Me (10)), displaying κ1-N 1-pyridylpyrazolate coordination. A 5-trifluoromethyl substituent causes N1-to-N2 slide. Thus, 3-(2-pyridyl)-5-trifluoromethylpyrazole affords equilibria between Pt{κ3-N,C,N-[py-C6HR2-py]}{κ1-N 1-[CF3pz-py]} (R = H (11a), Me (12a)) and Pt{κ3-N,C,N-[py-C6HR2-py]}{κ1-N 2-[CF3pz-py]} (R = H (11b), Me (12b)). 1,3-Bis(2-pyridyloxy)phenyl allows the chelating coordination of the incoming anions. Deprotonations of 3-(2-pyridyl)pyrazole and its substituted 5-methyl counterpart promoted by 6 lead to equilibria between Pt{κ3-N,C,N-[pyO-C6H3-Opy]}{κ1-N 1-[R′pz-py]} (R′ = H (13a), Me (14a)) with a κ-N 1-pyridylpyrazolate anion, keeping the pincer coordination of the di(pyridyloxy)aryl ligand, and Pt{κ2-N,C-[pyO-C6H3(Opy)]}{κ2-N,N-[R′pz-py]} (R′ = H (13c), Me (14c)) with two chelates. Under the same conditions, 3-(2-pyridyl)-5-trifluoromethylpyrazole generates the three possible isomers: Pt{κ3-N,C,N-[pyO-C6H3-Opy]}{κ1-N 1-[CF3pz-py]} (15a), Pt{κ3-N,C,N-[pyO-C6H3-Opy]}{κ1-N 2-[CF3pz-py]} (15b), and Pt{κ2-N,C-[pyO-C6H3(Opy)]}{κ2-N,N-[CF3pz-py]} (15c). The N1-pyrazolate atom produces a remote stabilizing effect on the chelating form, pyridylpyrazolates being better chelate ligands than pyridylpyrrolates. Accordingly, reactions of 4–6 with 2-(2-pyridyl)-3,5-bis(trifluoromethyl)pyrrole yield Pt{κ3-N,C,N-[py-C6HR2-py]}{κ1-N 1-[(CF3)2C4(py)HN]} (R = H (16), Me (17)) or Pt{κ3-N,C,N-[pyO-C6H3-Opy]}{κ1-N 1-[(CF3)2C4(py)HN]} (18), displaying κ1-N 1-pyrrolate coordination. Complexes 7–10 are efficient green phosphorescent emitters (488–576 nm). In poly(methyl methacrylate) (PMMA) films and in dichloromethane, they experience self-quenching, due to molecular stacking. Aggregation occurs through aromatic π–π interactions, reinforced by weak platinum–platinum interactions.

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Experimental and Theoretical Study of Ni^II‐ and Pd^II‐Promoted Double Geminal C(sp³)−H Bond Activation Providing Facile Access to NHC Pincer Complexes: Isolated Intermediates and Mechanism

Gourlaouen

Pang

et al. 2022

Chemistry A European J

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We report the first examples of metal-promoted double geminal activation of C(sp 3 )À H bonds of the NÀ CH 2 À N moiety in an imidazole-type heterocycle, leading to nickel and palladium N-heterocyclic carbene complexes under mild conditions. Reaction of the new electron-rich diphosphine 1,3-bis((di-tert-butylphosphaneyl)methyl)-2,3-dihydro-1Hbenzo[d]imidazole (1) with [PdCl 2 (cod)] occurred in a stepwise fashion, first by single CÀ H bond activation yielding the alkyl pincer complex [PdCl(PC sp 3 H P)] (3) with two trans phosphane donors and a covalent PdÀ C sp 3 bond. Activation of the CÀ H bond of the resulting α-methine C sp 3 HÀ M group occurred subsequently when 3 was treated with HCl to yield the NHC pincer complex [PdCl(PC NHC P)]Cl (2). Treatment of 1 with [NiBr 2 (dme)] also afforded a NHC pincer complex, [NiBr(PC NHC P)]Br ( 6), but the reactions leading to the double geminal CÀ H bond activation of the NÀ CH 2 À N group were too fast to allow identification or isolation of an intermediate analogous to 3. The determination of six crystal structures, the isolation of reaction intermediates and DFT calculations provided the basis for suggesting the mechanism of the stepwise transformation of a NÀ CH 2 À N moiety in the NÀ C NHC À N unit of NHC pincer complexes and explain the key differences observed between the Pd and Ni chemistries.

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Recent advances in the chemistry of group 9—Pincer organometallics

Cited by 9 publications

References 671 publications

Direct Heterogenization of the Ru-Macho Catalyst for the Chemoselective Hydrogenation of α,β-Unsaturated Carbonyl Compounds

Direct Heterogenization of the Ru-Macho Catalyst for the Chemoselective Hydrogenation of α,β-Unsaturated Carbonyl Compounds

Competition between N,C,N-Pincer and N,N-Chelate Ligands in Platinum(II)

Experimental and Theoretical Study of Ni^II‐ and Pd^II‐Promoted Double Geminal C(sp³)−H Bond Activation Providing Facile Access to NHC Pincer Complexes: Isolated Intermediates and Mechanism

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Recent advances in the chemistry of group 9—Pincer organometallics

Cited by 9 publications

References 671 publications

Direct Heterogenization of the Ru-Macho Catalyst for the Chemoselective Hydrogenation of α,β-Unsaturated Carbonyl Compounds

Direct Heterogenization of the Ru-Macho Catalyst for the Chemoselective Hydrogenation of α,β-Unsaturated Carbonyl Compounds

Competition between N,C,N-Pincer and N,N-Chelate Ligands in Platinum(II)

Experimental and Theoretical Study of NiII‐ and PdII‐Promoted Double Geminal C(sp3)−H Bond Activation Providing Facile Access to NHC Pincer Complexes: Isolated Intermediates and Mechanism

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Experimental and Theoretical Study of Ni^II‐ and Pd^II‐Promoted Double Geminal C(sp³)−H Bond Activation Providing Facile Access to NHC Pincer Complexes: Isolated Intermediates and Mechanism