A study of the inclusion properties of 1,2-bis(diphenylphosphinoselenoyl)ethane and related host molecules

Abstract

The title compound (I) has been found to form stable adducts when recrystallised from various pure solvents. Most significantly, host (I) exhibits a remarkably high selectivity for certain para-disubstituted aromatic molecules. For example, recrystallisation of (I) from an equimolar mixture of each of the xylenes, and ethylbenzene leads to incorporation of 97.5% of p-xylene. An X-ray investigation of the inclusion compound of (I) with p-xylene has been carried out. Crystals are triclinic, space group P1, with a= 8.958(1), b= 14.822(2), c= 15.496(2)Å, α= 81.20(1)°, β= 83.05(1)°, γ= 79.38(1)°, with three host and a single guest molecule in the unit cell. The structure was refined by least-squares methods to a final R of 0.036 for 2 558 significant diffractometer data. The adduct is of the true clathrate type, the highly ordered p-xylene guest being accommodated in an effectively closed cage. Compounds (II)–(V) which are structurally related to (I) have also been prepared and found to exhibit inclusion behaviour, but to a lesser degree than (I).