A THEORETICAL COMPARISON OF PHOSPHINO AND AMINO-GROUPS IN THE ISOCYANIDE-CYANIDE REARRANGEMENT

Ab initio molecular orbital calculations have been used to study the i socyanide-cyanide rearrangement involving the migration of the hydroge n, amino and phosphino groups. Geometries were optimized using MP2/6-3 11 G (d,p) while relative energies were obtained from CISDQ/6-311 + G (d,p) wavefunctions. Structures and some spectroscopic properties of the equilibrium structures are predicted. Phosphinoisocyanide is foun d to lie 16 +/- 2 kcal mol(-1) above phosphinocyanide, and to rearrang e to the latter with an energy barrier of 27 +/- 2 kcal mol(-1). Energ etics (kcal mol(-1)) of two other rearrangements are as follows: isocy anamide (0) --> TS (37) --> cyanamide (-44) and hydrogen isocyanide (0 ) --> TS (30) --> hydrogen cyanide (-14). Phosphinoisocyanide exhibits kinetic and thermodynamic stability similar to hydrogen isocyanide (r elative to their isomers) and should thus be detectable in both gaseou s and condensed phases.