Unexpected reactivity of a PONNOP ‘expanded pincer’ ligand

Scheerder, Arthur R.; Lutz, Martin; Broere, Daniël L. J.

doi:10.1039/d0cc02166k

Cited by 17 publications

(53 citation statements)

References 38 publications

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“…The major species observed in each case is a linear tricopper complex, [Cu 3 (DPENO) 2 ]NTf 2 , bearing two naphthyridine-based ligands resulting from cleavage of the P–O bond of the DPEOPN side arm, as evidenced by 1 H NMR spectroscopy, ESI-MS, and X-ray crystallography (Scheme ). Cleavage of DPEOPN’s P–O bond was also observed when [ 1b ]NTf 2 was treated with lithium benzoate or potassium tert -butoxide (Figure S24), and a similar P–O bond cleavage was reported recently by Broere et al As with other naphthyridine-based linear tricopper assemblies, − the Cu···Cu distance in [Cu 3 (DPENO) 2 ]NTf 2 (2.5510(3) Å) is relatively standard for a ligand-supported Cu I –Cu I cuprophilic interaction …”

Section: Resultssupporting

confidence: 78%

Unsymmetrical Naphthyridine-Based Dicopper(I) Complexes: Synthesis, Stability, and Carbon–Hydrogen Bond Activations

et al. 2021

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Two unsymmetrical dinucleating naphthyridine-based ligands with di(pyridyl) and phosphino side arms were employed in the synthesis of dicopper(I) chloride cores that activate NaBPh 4 to afford bridging phenyl organocopper complexes. In these compounds, the bridging ligand binds symmetrically, as observed in previously described symmetrical dicopper(I) complexes supported by naphthyridine-based ligands with two di(pyridyl) side arms. Unlike the symmetrical systems, however, these complexes undergo quasireversible electrochemical reductions, and chemical reduction yields a diamagnetic product resulting from the coupling of naphthyridine-based radicals of two complexes. The μ-Ph complexes activate the C−H bonds of terminal alkynes and the electron-poor arene C 6 F 5 H. By DFT calculations, the mechanism of terminal alkyne activation involves H-atom transfer at the cationic dicopper center and is sensitive to subtle changes in copper-ligand interactions as well as the position of the anion.

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Section: Resultssupporting

confidence: 78%

Unsymmetrical Naphthyridine-Based Dicopper(I) Complexes: Synthesis, Stability, and Carbon–Hydrogen Bond Activations

et al. 2021

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“…85 Utilizing a related NDI ligand, Bera and co-workers have recently reported a dicopper(I) complex that is active for catalytic alcohol dehydrogenation. 44 Use of symmetrical diphosphino-substituted naphthyridine ligands has been explored by Broere and co-workers, who obtained dicopper(I) complexes that bind ligands in the bridging position, 86,87 as was observed for the DPFN-supported compounds. In addition, in a manner similar to that of the Milstein group explored with related PNP ligands, 88 Broere and co-workers reported deprotonations of the methylene-linked phosphine side-arms, which led to activation of H 2 and isolation of a bridging mesityl complex, analogous to our DPFN-based phenyl complex 10.…”

Section: ■ Unsymmetrical Ligandsmentioning

confidence: 99%

Bimetallics in a Nutshell: Complexes Supported by Chelating Naphthyridine-Based Ligands

et al. 2020

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Conspectus: Bimetallic motifs are a structural feature common to some of the most effective and synthetically useful catalysts known, including in the active sites of many metalloenzymes and on the surfaces of industrially relevant heterogeneous materials. However, the complexity of these systems often hampers detailed studies of their fundamental properties. To glean valuable mechanistic insight into how these catalysts function, this research group has prepared a family of dinucleating 1,8-naphthyridine ligands that bind two first-row transition metals in close proximity, originally designed to help mimic the proposed active site of metal oxide surfaces. Of the various bimetallic combinations examined, dicopper(I) is particularly versatile, as neutral bridging ligands adopt a variety of different binding modes depending on the configuration of frontier orbitals available to interact with the Cu centers. Organodicopper complexes are readily accessible, either through the traditional route of salt metathesis or via the activation of tetraarylborate anions through aryl group abstraction by a dicopper(I) unit. The resulting bridging aryl complexes engage in C-H bond activations, notably with terminal alkynes to afford bridging alkynyl species. The µhydrocarbyl complexes are surprisingly tolerant of water and elevated temperatures. This stability was leveraged to isolate a species that typically represents a fleeting intermediate in Cu-catalyzed azide-alkyne coupling (CuAAC); reaction of a bridging alkynyl complex with an organic azide afforded the first example of a well-defined, symmetrically bridged dicopper triazolide. This complex was shown to be an intermediate during CuAAC, providing support for a proposed bimetallic mechanism. These platforms are not limited to formally low oxidation states; chemical oxidation of the hydrocarbyl complexes cleanly results in formation of mixed-valent Cu I Cu II complexes with varying degrees of distortion in both the bridging moiety and the dicopper core. Higher oxidation states, i.e. dicopper(II), are easily accessed via oxidation of a dicopper(I) compound with air to give a Cu II 2(µ-OH)2 complex. Reduction of this compound with silanes resulted in the unexpected formation of pentametallic copper(I) dihydride clusters or trimetallic monohydride complexes, depending on the nature of the silane. Finally, development of an unsymmetrical naphthyridine ligand with mixed donor side-arms enables selective synthesis of an isostructural series of six heterobimetallic complexes, demonstrating the power of ligand design in the preparation of heterometallic assemblies.

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“…However, the chemical shifts observed for 2H do not map well on those in the ostensibly related N-P i Pr 2 and O-P i Pr 2 compounds (Figure 5). The 31 P NMR chemical shifts for the i Pr 2 PÀ O fragments in L1, [14] L2, [ 15 ] and L3 [16] appear at ca. 140-150 ppm and for the i Pr 2 PÀ N fragments in L4, [ 17 ] L5, and L6 [18] at ca.…”

Section: Synthesis and Characterization Of Nucleopincers Based On Uracil And Thyminementioning

confidence: 99%

Nucleopincers? Rhodium Complexes of Pyrimidine‐centered PNP Pincer Ligands Derived from Nitrogenous Nucleobases Uracil and Thymine

Günther

Kosanovich

Cao

et al. 2021

Zeitschrift anorg allge chemie

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This manuscript describes the synthesis and characterization of PONOP ligands from uracil and thymine. Rhodium chloride complexes of the ligands were synthesized and characterized by solution NMR and solid‐state X‐Ray crystallography. Cationic CO complexes were generated in situ to understand the electronic properties of these ligands and it was found that these are among the least donating of the neutral PNP type ligands at this time.

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Unexpected reactivity of a PONNOP ‘expanded pincer’ ligand

Abstract: A PONNOP ‘expanded pincer’ ligand is described that can bind two copper(i) atoms in close proximity, but undergoes an unexpected rearrangement in the presence of nickel(ii) salts.

Cited by 17 publications

References 38 publications

Unsymmetrical Naphthyridine-Based Dicopper(I) Complexes: Synthesis, Stability, and Carbon–Hydrogen Bond Activations

Unsymmetrical Naphthyridine-Based Dicopper(I) Complexes: Synthesis, Stability, and Carbon–Hydrogen Bond Activations

Bimetallics in a Nutshell: Complexes Supported by Chelating Naphthyridine-Based Ligands

Nucleopincers? Rhodium Complexes of Pyrimidine‐centered PNP Pincer Ligands Derived from Nitrogenous Nucleobases Uracil and Thymine

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