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

Different reactions of Mes* substituted phosphanes (Mes* = 2,4,6-tri-tert-butylphenyl) led to the formation of the bicyclic tetraphosphane Mes*P(4)Mes* (5) and its unknown Lewis acid adduct 5 center dot 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 P-4 scaffold from P-1 building blocks (i.e. primary phosphanes) or by reactions starting from P-2 or P-4 scaffolds (i.e. a diphosphene or cyclic tetraphosphane). Furthermore, interconversion between the exo-exo and endo-exo isomer were studied by P-31 NMR spectroscopy. All compounds were fully characterized by experimental as well as computational methods.