Naslov
1, 8-Bis(hexamethyl-triamino-phosphazenyl)naphthalene, HMPN: A Superbasic Bisphosphazene "Proton Sponge"

Autori
Raab, Volker ; Gauchenova, Ekaterina ; Merkoulov, Alexei ; Harms, Klaus ; Sundermeyer, Jorg ; Kovačević, Borislav ; Maksić, Zvonimir

Izvornik
Journal of the American Chemical Society (0002-7863) 127 (2005), 45; 15738-15743

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Basicity; Peralkylated phosphazenes; Protonation; Proton sponge; Hydrogen bonding

Sažetak
It is shown that a combination of Schwesinger's phosphazene base concept and the idea of the disubstituted 1, 8-naphthalene spacer, first introduced by Alder in paradigmatic 1, 8-bis(dimethylamino)naphthalene (DMAN), yields a new superbase HMPN, which represents the up to date most basic representative of this class of "proton sponges" as evidenced by the theoretically estimated proton affinity PA = 274 kcal/mol and the measured pKBH+ (MeCN) 29.9 +0.2. HMPN is by nearly twelve orders of magnitude more basic than Alder's classical 1, 8-bis-(dimethylamino)naphthalene (DMAN). The title compound HMPN is prepared and fully characterized. The spatial structure of HMPN and its conjugate acid is determined by X-ray technique and theoretical DFT calculations. It is found that mono-protonated HMPN has an unsymmetrical intramolecular hydrogen bridge (IHB). This cooperative proton chelating effect renders the bis-phosphazene more basic than Schwesinger's set of "mono-dentate" P1 phosphazene bases. The density functional calculations are in good accordance with the experimental results, providing some complementary information. They conclusively show that the high basicity of HMPN is a consequence of the high energy content of the base in its initial neutral state and the intramolecular hydrogen bonding in the resulting conjugate acid with contributions to proton affinity of 14.1 and 9.5 kcal/mol, respectively.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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