Ab initio and density functional study of four-membered platina- and pallada-cycles, , X: CO, CNH, CNH 2+, P(O)H, SO and SO 2

Abstract

Ab initio and density functional calculations for the four-membered platina- and pallada-cycles of the type ▪ (X: CO, CNH, CNH 2 +, P(O)H, SO, SO 2) showed that the coordination about metal is square planar. The ▪ ring is non-planar, as measured by the fold angle between the planes C–M–C and C–X–C, in all complexes except that of metallathietane-3,3-dioxide complexes (X=SO 2). The theoretical results agree well with the experimental data. The structures with a planar ▪ ring are transition states connecting the puckered minima. The computations reveal a low-energy reaction path for the ring inversion. The results of the natural population analysis and the calculation of the metal–ligand dissociation energies revealed that the metal–ligand interaction is stronger in the platinum complexes. The dissociation energy increases for X: CO, CNH, CNH 2 + and decreases for X: P(O)H, SO, SO 2 as the metallacycle ring becomes more puckered.