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.