3 research outputs found
Experimental Basicities of Phosphazene, Guanidinophosphazene, and Proton Sponge Superbases in the Gas Phase and Solution
Experimental
gas-phase superbasicity scale spanning 20 orders of
magnitude and ranging from bicyclic guanidine 7-methyl-1,5,7-triazabicyclo[4.4.0]Âdec-5-ene
to triguanidinophosphazenes and P<sub>3</sub> phosphazenes is presented
together with solution basicity data in acetonitrile and tetrahydrofuran.
The most basic compound in the scaleî—¸triguanidinophosphazene
Et–Nî—»PÂ[Nî—»CÂ(NMe<sub>2</sub>)<sub>2</sub>]<sub>3</sub>î—¸has the highest experimental gas-phase basicity of
an organic base ever reported: 273.9 kcal mol<sup>–1</sup>.
The scale includes besides the higher homologues of classical superbasic
phosphazenes and several guanidino-substituted phosphazenes also a
number of recently introduced bisphosphazene and bis-guanidino proton
sponges. This advancement was made possible by a newly designed Fourier
transform ion cyclotron resonance (ICR) mass spectrometry setup with
the unique ability to generate and control in the ICR cell sufficient
vapor pressures of two delicate compounds having low volatility, which
enables determining their basicity difference. The obtained experimental
gas-phase and solution basicity data are analyzed in terms of structural
and solvent effects and compared with data from theoretical calculations