The aim of the project lies in the synthesis of acyclic, cyclic and cage-shaped molecules with backbones composed
of the elements silicon and phosphorus. Valencies outside the backbone are saturated with hydrogen only, the
molecules thus contain SiH and PH bonds. With the general composition Pn Si m Ho (n, m, o = 1 - 10) they
constitute the parent molecules of organosubstituted silylphosphanes and phosphanylsilanes known for quite a long
time. Despite their fundamental importance for basic science, only a small number of molecules are known at
present and systematic procedures for their preparation are virtually absent from the literature. A further important
aim of the project is the investigation of their molecular properties with spectroscopic methods and quantum
chemical calculations.
In the project, the dependence of the silicon-phosphorus NMR coupling constant 1J(SiP) in silylphosphanes X3Si-PH2 and in the phosphonium ions [X3Si-PH3]+ with X = H, F, Cl, Br, I, CH3 und SiH3 was investigated with quantum chemical calculations. For the phosphonium ions, a linear dependence of the coupling constants on the sum of the electronegativities of the substituents X was established. Due to the lone electron pair on the P-atom, this is not the case for the silylphosphanes themselves. It was also found that the coupling constants in the silylphosphanes Cl2HSiPH2 und ClH2SiPH2 depend strongly on the molecular conformations, i. e. on the dihedral angles Cl-Si-P-lone pair.