Synthetic strategies to bicyclic tetraphosphanes using P1, P2 and P4 building blocks

Abstract

Different reactions of Mes∗ substituted phosphanes (Mes∗ = 2,4,6-tri-tert-butylphenyl) led to the formation of the bicyclic tetraphosphane Mes∗P4Mes∗ (5) and its unknown Lewis acid adduct 5·GaCl3. In this context, the endo-exo isomer of 5 was fully characterized for the first time. The synthesis was achieved by reactions involving "self-assembly" of the P4 scaffold from P1 building blocks (i.e. primary phosphanes) or by reactions starting from P2 or P4 scaffolds (i.e. a diphosphene or cyclic tetraphosphane). Furthermore, interconversion between the exo-exo and endo-exo isomer were studied by 31P NMR spectroscopy. All compounds were fully characterized by experimental as well as computational methods.