The role of 3d orbitals in the bonding of phosphorus compounds

Ab initio LCAO-MO-SCF calculations for several typical molecules containing phosphorushave been undertaken to study the role of phosphorus 3d orbitals in the bonding.It is emphasizedthat the discussion about the 3d orbital participation in bonding should be based on a reasonable choiceof basis sets and it seems suitable to choose the atomic orbitals in proper molecular environment asthe basis set.As an approximation,the optimized minimal STO-NG basis sets have been adoptedin the present paper.The results obtained well exhibit the model of 3d orbital participation in bonding.It is shown that under the influence of highly electronegative ligands the phosphorus 3d orbitals con-tract greatly,their energy levels drop considerably,and thus they can effectively participate in bond-ing.The presence of highly electronegative ligands seems necessary.The contribution of 3d orbitalsto bonding is achieved mainly through the concertedformation of σ bonds and p-d backbonds,thoughthe contribution to σ bonding is minor.The three-center,four-electron bond modelis only approxi-mately correct.The results of the present paper demonstrate that the model of 3d orbital participationin bonding favoured by experimental chemists is reasonable and possesses sound ground.

The role of 3d orbitals in the bonding of phosphorus compounds

Ab initio LCAO-MO-SCF calculations for several typical molecules containing phosphorus have been undertaken to study the role of phosphorus 3d orbitals in the bonding. It is emphasized that the discussion about the 3d orbital participation in bonding should be based on a reasonable choice of basis sets and it seems suitable to choose the atomic orbitals in proper molecular environment as the basis set. As an approximation, the optimized minimal STO-NG basis sets have been adopted in the present paper. The results obtained well exhibit the model of 3d orbital participation in bonding. It is shown that under the influence of highly electronegative ligands the phosphorus 3d orbitals contract greatly, their energy levels drop considerably, and thus they can effectively participate in bonding. The presence of highly electronegative ligands seems necessary. The contribution of 3d orbitals to bonding is achieved mainly through the concerted formation of σ bonds and p-d backbonds, though the contribution to σ bonding is minor. The three-center, four-electron bond model is only approximately correct. The results of the present paper demonstrate that the model of 3d orbital participation in bonding favoured by experimental chemists is reasonable and possesses sound ground.