Structures, energetics and vibrational spectra of the valence isomers of phosphinine. An ab initio and DFT study

The structures and energetics of nine valence isomers of phosphinine, (CH)( 5)P, have been investigated by ab initio (HF, MP2 and CCSD(T)) and hybrid d ensity functional (B3LYP) methods. The relative stability ordering of the ( CH)(5)P isomers is similar to those of (CH)(6). Strain energies are evaluat ed for all the non-planar isomers based on the sum of standard bond strengt hs, taking the planar resonance stabilized isomer, phosphinine as the refer ence. Lower magnitudes of the frequencies corresponding to the first few no rmal modes compared to their benzene isomers account for smoother isomeriza tion reactions among them. (C) 2001 Published by Elsevier Science B.V.