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Selective Transformation of Nickel-Bound Formate to CO or C-C Coupling Products Triggered by Deprotonation and Steered by Alkali-Metal Ions.

ABSTRACT: The complexes [L^tBu Ni(OCO-?² O,C)]M₃ [N(SiMe₃ )₂ ]₂ (M=Li, Na, K), synthesized by deprotonation of a nickel formate complex [L^tBu NiOOCH] with the corresponding amides M[N(SiMe₃ )₂ ], feature a Ni^II -CO₂ ^2- core surrounded by Lewis-acidic cations (M⁺ ) and the influence of the latter on the behavior and reactivity was studied. The results point to a decrease of CO₂ activation within the series Li, Na, and K, which is also reflected in the reactivity with Me₃ SiOTf leading to the liberation of CO and formation of a Ni-OSiMe₃ complex. Furthermore, in case of K⁺ , the {[K₃ [N(SiMe₃ )₂ ]₂ }⁺ shell around the Ni-CO₂ ^2- entity was shown to have a large impact on its stabilization and behavior. If the number of K[N(SiMe₃ )₂ ] equivalents used in the reaction with [L^tBu NiOOCH] is decreased from 3 to 0.5, the deprotonated part of the precursor enters a complex reaction sequence with formation of [L^tBu Ni^I (?-OOCH)Ni^I L^tBu ]K and [L^tBu Ni(C₂ O₄ )NiL^tBu ]. The same reaction at higher concentrations additionally led to the formation of a unique hexanuclear Ni^II complex containing both oxalate and mesoxalate ([O₂ C-CO₂ -CO₂ ]^4- ) ligands.

SUBMITTER: Zimmermann P

PROVIDER: S-EPMC7898393 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature

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Selective Transformation of Nickel-Bound Formate to CO or C-C Coupling Products Triggered by Deprotonation and Steered by Alkali-Metal Ions.

Zimmermann Philipp P Ar Deniz D Rößler Marie M Holze Patrick P Cula Beatrice B Herwig Christian C Limberg Christian C

Angewandte Chemie (International ed. in English) 20201130 5

The complexes [LtBu Ni(OCO-κ2 O,C)]M3 [N(SiMe3 )2 ]2 (M=Li, Na, K), synthesized by deprotonation of a nickel formate complex [LtBu NiOOCH] with the corresponding amides M[N(SiMe3 )2 ], feature a NiII -CO2 2- core surrounded by Lewis-acidic cations (M+ ) and the influence of the latter on the behavior and reactivity was studied. The results point to a decr ...[more]

PMID: 33084156

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Project description:Quantum chemical calculations were carried out for deprotonated (P-) and protonated purine (PH+) and for adducts with one alkali metal cation (P-M+ and PM+, where M+ is Li+ or Na+) in the gas phase {B3LYP/6-311+G(d,p)}, a model of perfectly apolar environment, and for selected structures in aqueous solution {PCM(water)//B3LYP/6-311+G(d,p)}, a reference polar medium for biological studies. All potential isomers of purine derivatives were considered, the favored structures indicated, and the preferred sites for protonation/deprotonation and cationization reactions determined. Proton and metal cation basicities of purine in the gas phase were discussed and compared with those of imidazole and pyrimidine. Bond-length alternations in the P, PH+, P-M+, and PM+ forms were quantitatively measured using the harmonic oscillator model of electron delocalization (HOMED) indices and compared with those for P. Variations of the HOMED values when proceeding from the purine structural building blocks, pyrimidine and imidazole, to the bicyclic purine system were also examined. Generally, the isolated NH isomers exhibit a strongly delocalized ?-system (HOMED >?0.8). Deprotonation slightly increases the HOMED values, whereas protonation and cationization change the HOMED indices in different way. For bidentate M+-adducts, the HOMED values are larger than 0.9 like for the largely delocalized P-. The HOMED values correlate well in a comprehensive relationship with the relative Gibbs energies (?G) calculated for individual isomers whatever the purine form is, neutral, protonated, or cationized. When PCM-DFT model was utilized for P-, PH+, PM+, and P-M+ (M+?=?Li+) both electron delocalization and relative stability are different from those for the molecules in vacuo. The solvation effects cause a slight increase in HOMEDs, whereas the ?Es decrease, but in different ways. Hence, contribution of particular isomers in the isomeric mixtures of PH+, PM+, and P-M+ also varies. HOMED variations for the favored neutral, deprotonated, protonated, and lithiated forms of purine in the gas phase and aqueous solution.

Dataset Information

Selective Transformation of Nickel-Bound Formate to CO or C-C Coupling Products Triggered by Deprotonation and Steered by Alkali-Metal Ions.

Publications

Selective Transformation of Nickel-Bound Formate to CO or C-C Coupling Products Triggered by Deprotonation and Steered by Alkali-Metal Ions.

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