STRUCTURE AND FLEXIBILITY OF SYMMETRICAL HETEROCYCLOPENTENES

From an ab initio investigation of the equilibrium structures of heter ocyclopentanes with substituting moieties X (X is CH2, NH, O, Si, SiH2 , PH, P(O)H, S, SH2, SO and SO2), it was found that at the MP2/6-31G level the qualitative structural predictions are in accord with the re sults obtained from the analysis of the vibrational and microwave data . The rings where X is O, Si, SiH2, S and SH2 are planar. The present calculations provide the first structural data for most of the systems studied here. Among the hitherto uninvestigated compounds, the one wh ere X is SH2 is strongly planar, while 3-phospholene-1-oxide, an impor tant precursor in organophosphorus chemistry, seems to be quite floppy . (C) 1997 Elsevier Science B.V.