N-Atom transfer via thermal or photolytic activation of a Co-azido complex with a PNP pincer ligand

Vreeken, Vincent; Baij, Lambert; Bruin, Bas de; Siegler, Maxime A.; Vlugt, Jarl Ivar van der

doi:10.1039/c7dt01712j

Cited by 32 publications

(27 citation statements)

References 51 publications

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“…[9] A transient paramagnetic cobalt–imido complex was spectroscopically assigned by Caulton and co‐workers at −40 °C that rapidly underwent rearrangement by P−N bond formation at temperatures above −20 °C [10] . More recently, van der Vlugt and co‐workers implicated a cobalt–nitrido intermediate en route to P−N bond formation [11] . Our laboratory has also described the generation of a cobalt nitride supported by a pyridine(diimine) ligand that underwent intramolecular C−H addition [12] .…”

Section: Methodsmentioning

confidence: 99%

Synthesis, Electronic Structure, and Reactivity of a Planar Four‐Coordinate, Cobalt–Imido Complex

et al. 2021

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A four‐coordinate cobalt–imido complex, (tBumPNP)Co=NMes (tBumPNP=modified PNP pincer ligand) has been synthesized from addition of 2,4,6‐trimethylphenylazide (Mes–N3) to the corresponding dinitrogen complex. The solid‐state structure determined by X‐ray diffraction established a rare, idealized planar geometry with a Co=N bond distance of 1.716(2) Å. Magnetic measurements revealed an S=1 ground state with CAS‐SCF calculations supporting radical character on the imide nitrogen. Thermolysis of the cobalt–imido compound induced selective insertion of the imido group into a Co−P bond and yielded a three‐coordinate cobalt complex with a distorted T‐shaped geometry. Transition state analysis conducted with DFT calculations established the thermodynamic stability of the P–N coupled product and provided insight into the exclusive selectivity.

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Section: Methodsmentioning

confidence: 99%

Synthesis, Electronic Structure, and Reactivity of a Planar Four‐Coordinate, Cobalt–Imido Complex

et al. 2021

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“…In addition to their industrial relevance, low-nuclearity cobalt nitrides are of interest because of their rarity and high reactivity. A pair of terminal nitrides have been proposed in the literature, , and another terminal nitride was observed by electron paramagnetic resonance spectroscopy, following photolysis at 10 K . These species all appear to undergo intramolecular electrophilic reactivity, including C–H activation or other proton-coupled electron transfer (PCET) chemistry.…”

Section: Introductionmentioning

confidence: 97%

“…In addition to their industrial relevance, low-nuclearity cobalt nitrides are of interest because of their rarity and high reactivity. A pair of terminal nitrides have been proposed in the literature, 23,24 electron paramagnetic resonance spectroscopy, following photolysis at 10 K. 25 These species all appear to undergo intramolecular electrophilic reactivity, including C−H activation or other proton-coupled electron transfer (PCET) chemistry. Recently, Fortier and co-workers described the first example of an isolable dicobalt bridging nitride, This species was found to be capable of intermolecular reactivity with C−H bonds and H 2 .…”

Section: ■ Introductionmentioning

confidence: 99%

Mapping the Reactivity of Dicobalt Bridging Nitrides in Constrained Geometries

Spentzos

Tomson

2021

Inorg. Chem.

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Low-nuclearity nitrides of the late transition metals are rare and reactive molecular species, with little experimental precedent. The first putative examples of dicobalt bridging nitrides,; PDI = pyridyldiimine; n = 2 or 3, representing the length of the aliphatic chain linking PDI imino groups), were reported recently and shown to undergo a range of intramolecular reaction pathways, including N− H bond formation, C−H bond insertion, and PN bond formation at the bridging nitride. The specific mode of reactivity changed with the phase of the reaction and the size of the macrocycle used to support the transient species. The present contribution offers a computational investigation into both the geometric and electronic structures of these nitrides as well as the factors governing their reaction selectivity. The compounds n [Co 2 N] 3+ exhibit μ-N-based lowest unoccupied molecular orbitals (LUMOs) that are consistent with subvalent, electrophilic nitrides. The specific orientations of the LUMOs induce ring-size-dependent stereoelectronic effects, thereby causing the product selectivity observed experimentally. Notably, the nitrides also exhibit a degree of nucleophilicity at μ-N by way of a high-energy, μ-N-based lone pair. This ambiphilic character appears to be a direct result of the constrained environment imposed by the folded-ligand geometries of n [Co 2 N] 3+ . When combined with the experimental findings, these data led to the conclusion that the folded-ligand isomers are the reactive species and that the constrained geometry imposed by the macrocyclic ligand plays an important role in controlling the reaction outcome.

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“…Transition metals generally enable milder conditions for the formation of nitrenes and higher selectivity in their subsequent transfer. The majority of nitrene-transfer studies are focused on middle and late transition metals, which generally feature weaker metal-imido bonds and therefore exhibit more reactive nitrene functionalities [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. In contrast, early transition metals (particularly chromium) typically exhibit less reactive nitrene functionalities due to the stability of multiple metal-nitrogen bonds [22][23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Chromium(II) Complexes with Chelating Bis(alkoxide) Ligand and Their Reactions with Organoazides and Diazoalkanes

et al. 2020

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Synthesis of new chromium(II) complexes with chelating bis(alkoxide) ligand [OO]Ph (H2[OO]Ph = [1,1′:4′,1′’-terphenyl]-2,2′’-diylbis(diphenylmethanol)) and their subsequent reactivity in the context of catalytic production of carbodiimides from azides and isocyanides are described. Two different Cr(II) complexes are obtained, as a function of the crystallization solvent: mononuclear Cr[OO]Ph(THF)2 (in toluene/THF, THF = tetrahydrofuran) and dinuclear Cr2([OO]Ph)2 (in CH2Cl2/THF). The electronic structure and bonding in Cr[OO]Ph(THF)2 were probed by density functional theory calculations. Isolated Cr2([OO]Ph)2 undergoes facile reaction with 4-MeC6H4N3, 4-MeOC6H4N3, or 3,5-Me2C6H3N3 to yield diamagnetic Cr(VI) bis(imido) complexes; a structure of Cr[OO]Ph(N(4-MeC6H4))2 was confirmed by X-ray crystallography. The reaction of Cr2([OO]Ph)2 with bulkier azides N3R (MesN3, AdN3) forms paramagnetic products, formulated as Cr[OO]Ph(NR). The attempted formation of a Cr–alkylidene complex (using N2CPh2) instead forms chromium(VI) bis(diphenylmethylenehydrazido) complex Cr[OO]Ph(NNCPh2)2. Catalytic formation of carbodiimides was investigated for the azide/isocyanide mixtures containing various aryl azides and isocyanides. The formation of carbodiimides was found to depend on the nature of organoazide: whereas bulky mesitylazide led to the formation of carbodiimides with all isocyanides, no carbodiimide formation was observed for 3,5-dimethylphenylazide or 4-methylphenylazide. Treatment of Cr2([OO]Ph)2 or H2[OO]Ph with NO+ leads to the formation of [1,2-b]-dihydroindenofluorene, likely obtained via carbocation-mediated cyclization of the ligand.

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N-Atom transfer via thermal or photolytic activation of a Co-azido complex with a PNP pincer ligand

Cited by 32 publications

References 51 publications

Synthesis, Electronic Structure, and Reactivity of a Planar Four‐Coordinate, Cobalt–Imido Complex

Synthesis, Electronic Structure, and Reactivity of a Planar Four‐Coordinate, Cobalt–Imido Complex

Mapping the Reactivity of Dicobalt Bridging Nitrides in Constrained Geometries

Synthesis of Chromium(II) Complexes with Chelating Bis(alkoxide) Ligand and Their Reactions with Organoazides and Diazoalkanes

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