A new model compound for vitamin B12 coenzyme: synthesis and crystal structure of a tetraazamacrocyclic alkylcobalt(III) compound with a pendant coordinating alkyl arm

Kofod, Pauli; Moore, Peter; Alcock, Nathaniel W.; Clase, Howard J.

doi:10.1039/c39920001261

Cited by 10 publications

(6 citation statements)

References 6 publications

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“…Moreover, the crystal structure revealed a square-pyramidal arrangement of the coordination sphere of the cobalt ion. The Co–C bond length is 1.973 Å, which is typical of that found in other alkylcobalt(III) compounds . Furthermore, the photolysis of complex 7 in the presence of a radical trap (TEMPO) led to the formation of TEMPO adduct 6 in 53% yield, corroborating the hypothesis that under developed conditions the Co–C bond undergoes homolytic cleavage, generating an alkyl radical (Scheme C).…”

Section: Resultssupporting

confidence: 77%

Polarity-Reversal Strategy for the Functionalization of Electrophilic Strained Molecules via Light-Driven Cobalt Catalysis

et al. 2020

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Strain-release-driven methodology is a powerful tool for accessing structural motifs, highly desirable by the pharmaceutical industry. The reactivity of spring-loaded cyclic reagents is dominated by transformations relying on their inherent electrophilic reactivity. Herein, we present a polarity-reversal strategy based on light-driven cobalt catalysis, which enables the generation of nucleophilic radicals through strain release. The applicability of this methodology is demonstrated by the design of two distinct types of reactions: Giese-type addition and Co/Nicatalyzed cross-coupling. Moreover, a series of electrochemical, spectroscopic, and kinetic experiments as well as X-ray structural analysis of the intermediate alkylcobalt(III) complex give deeper insight into the mechanism of the reaction.

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Section: Resultssupporting

confidence: 77%

Polarity-Reversal Strategy for the Functionalization of Electrophilic Strained Molecules via Light-Driven Cobalt Catalysis

et al. 2020

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“…In another recent example involving a main-group-element cycloaddition of acetylene and phenylacetylene to a dianionic diiminate based germylene complex was reported by Driess and co-workers . Iron, titanium, and copper nacnac complexes have been reported to add oxygen- and nitrogen-containing unsaturated molecules across the metal and ligand CH. − Acetylacetonate complexes of Pd(II), Rh(I), and Ir(I) added the activated alkyne hexafluoro-2-butyne across the M and central CH as well, but unactivated alkynes did not react, and unlike our system, these are all d 8 metal reagents. , A number of macrocyclic compounds of Co, Rh, Fe, and Ru with ligands based on multiple β-diiminate units have been reported to undergo cycloadditions. − …”

Section: Resultsmentioning

confidence: 99%

Cycloaddition Reactions of Terminal Alkynes and Phosphaalkynes with an Isolable 5-Coordinate β-Diiminate Platinum(IV) Dihydrosilyl Complex

et al. 2009

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Combining (Cl-nacnac)Pt(H)(1-pentene) (Cl-nacnac = N-p-Cl-phenyl-β-diiminate) and HSiR3 (SiR3 = SiPh3, SiEt3, SiHPh2) leads to rapid displacement of 1-pentene; oxidative addition of the Si−H bond produces a stable 5-coordinate Pt(IV) silyl dihydride complex which has been isolated and characterized crystallographically. The 5-coordinate silyl dihydride platinum(IV) complex undergoes a cycloaddition reaction with either acetylene or phosphaalkyne to form a vinyl or phosphaalkenyl Pt(IV) product, respectively. One acetylenic carbon adds to the central methine carbon of the Cl-nacnac ligand and the other alkyne carbon or phosphorus coordinates to the vacant site of the d6 metal. Phosphaalkynes are polarized such that the carbon is at the negative end of the dipole; however we observe a final product that reflects a reversal of this normal polarity. The phosphorus is nucleophilic even after the cycloaddition reaction is complete, and its lone pair can be methylated by MeOTf (OTf = trifluoromethanesulfonate) or protonated by addition of HBF4·Et2O.

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“…Several studies report C-C coupling reactions between the nitrile carbon and the methylene carbon of β-diimine ligands in the presence of bases, which involve BDI intermediates (Scheme 33top). Finally, a number of complexes of multidentate macrocyclic ligands [147][148][149][150][151][152][153][154][155][156][157] have also been reported to undergo related cycloaddition reactions, representative examples of which are depicted in Scheme 34. 146 Fig.…”

Section: Scheme 30mentioning

confidence: 99%

On the non-innocence of “Nacnacs”: ligand-based reactivity in β-diketiminate supported coordination compounds

2016

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While β-diketiminate (BDI or 'nacnac') ligands have been widely adopted to stabilize a wide range of metal ions in multiple oxidation states and coordination numbers, in several occurrences these ligands do not behave as spectators and participate in reactivity. Besides unwanted decomposition processes, BDI redox non-innnocence and unusual metal-ligand cooperative activation of substrates yielding attractive reactivity have been reported. This feature article will provide a comprehensive analysis of the various transformations involving BDI ligand platforms in coordination compounds across the periodic table.

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A new model compound for vitamin B12 coenzyme: synthesis and crystal structure of a tetraazamacrocyclic alkylcobalt(III) compound with a pendant coordinating alkyl arm

Cited by 10 publications

References 6 publications

Polarity-Reversal Strategy for the Functionalization of Electrophilic Strained Molecules via Light-Driven Cobalt Catalysis

Polarity-Reversal Strategy for the Functionalization of Electrophilic Strained Molecules via Light-Driven Cobalt Catalysis

Cycloaddition Reactions of Terminal Alkynes and Phosphaalkynes with an Isolable 5-Coordinate β-Diiminate Platinum(IV) Dihydrosilyl Complex

On the non-innocence of “Nacnacs”: ligand-based reactivity in β-diketiminate supported coordination compounds

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