Theoretical Design of Cage Structures with Unusual Linear P=O→Si Interactions

Molecular design of cage phosphine oxides (6-phospha-1,3,9,12-tetrasila-bicyclo[4.4.4]tetradecan-6-oxides) with four Si-containing acceptor fragments and one P=O donor fragment was performed using density functional theory methods (B3PW91 and ωB97X-D). Substituents at the silicon and phosphorus atoms were selected to favor the existence of the structures in the endo form containing a P=O···Si interaction. The competition of four silicon atoms for bonding to the phosphoryl oxygen atom was used to assess the coordinating ability of the phosphoryl group and to determine the nature of the P=O bond in phosphine oxides.