- Nucleophilic reactivities of the anions of nucleobases and their subunits
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The kinetics of the reactions of different heterocyclic anions derived from imidazoles, purines, pyrimidines, and related compounds with benzhydrylium ions and structurally related quinone methides have been studied in DMSO and water. The second-order rate constants (logk2) correlated linearly with the electrophilicity parameters E of the electrophiles according to the correlation logk2 = sN(N+E) (H. Mayr, M. Patz, Angew. Chem. 1994, 106, 990-1010; Angew. Chem. Int. Ed. Engl. 1994, 33, 938-957) allowing us to determine the nucleophilicity parameters N and sN for these anions. In DMSO, the reactivities of these heterocyclic anions vary by more than six orders of magnitude and are comparable to carbanions, amide and imide anions, or amines. The azole anions are generally four to five orders of magnitude more reactive than their conjugate acids. Copyright
- Breugst, Martin,Corralbautista, Francisco,Mayr, Herbert
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supporting information; experimental part
p. 127 - 137
(2012/03/09)
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- Nitrenium ions as ligands for transition metals
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Unlike N-heterocyclic carbenes (NHCs), which are now used ubiquitously in metal-based chemistry, the nitrogen-derived analogue (in which a carbon is replaced with the isoelectronic nitrogen cation, a nitrenium ion) has remained elusive as a ligand for metals. This is especially intriguing, because several other main-group analogues of NHCs have been prepared, and have been shown to coordinate with transition-metal complexes. Here, we describe the preparation of several N-heterocyclic nitrenium ions that are isoelectronic and isostructural to NHCs, and study their ligand properties. The formation of relatively strong nitrenium-metal bonds is unambiguously confirmed, in solution by selective 15 N-labelling experiments, and in the solid state by X-ray crystallography. Experimental and computational studies of the electronic properties of this novel type of ligand suggest that they are poor σ-donors and good μ-acceptors.
- Tulchinsky, Yuri,Iron, Mark A.,Botoshansky, Mark,Gandelman, Mark
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supporting information; experimental part
p. 525 - 531
(2012/04/04)
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