An experimental and theoretical study of the basicity of tetra-tert-butyltetrahedrane

The gas-phase basicity (GB) of tetra-tert-butyltetrahedrane (tBu(4)THD) was determined by FT-ICR mass spectrometry and comparison with reference compo unds of known basicity. Its GB, 1035 +/- 10 kJmol(-1), makes tetra-tert-but yltetrahedrane one of the strongest bases reported so far. Ab initio calcul ations [B3LYP/6-31G(d) and B3LYP/6-311 + G(d,p)//6-31G(d)] have been carrie d out in order to compare the high experimental basicity of tBu(4)THD with that estimated theoretically. Both B3LYP/6-31G(d) and QCISD(T) calculations were used to determine the reaction path which connects the initial tetrah edrane - ammonium complex with the final products, protonated cyclobutadien e (CBDH+) and ammonia.