The role of the sulfur 3d orbitals in bond formation in sulfur-containing compounds

The role of the sulfur 3d orbitals in bond formation is discussed by taking into account the influence of the environment on the orbitals of the sulfur atom in the molecules. The calculation results of a series of prototype molecules containing sulfur such as SF₂ SF₄, NSF₃, SF₀, H₂S are reported. It is convincingly shown that in highly electronegative environment the energy levels of the sulfur 3d orbitals are reduced to the vicinity of those of the ligand valence orbitals and their spatial distributions are contracted to the bonding area, and therefore they can participate in bond formation to a certain extent, which is enhanced by the formation of the d-p π back bonds. It seems that the result reported in this paper is helpful for the solution of the long-standing debate about the sulfur 3d orbital participation in bond formation.     

磷的d轨道在H~3PO分子中的作用

用分子片轨道在分子环境中发生极化的概念研究d轨道在H~3PO分子中的作用。H~3PO分子被分为两个分子片---H~3P和O.在RHF/6-31G^*水平上计算出分子环境中的极化了的分子片轨道(FOM)。再剔除d函数为主的FOM,用剩余的FOM为基进行构型优化,得到与RHF/6-31G^*相近的结果。这一结果说明磷原子的d函数在H~3PO分子中仅仅起一个极化函数的作用,而不是起价轨道作用。     

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.     

Inclusion of 3d orbitals in calculations involving second row atoms

Valence-state ionisation potentials, I , and non-empirical one-centre electron repulsion integrals are evaluated for the separate 3s, 3p and 3d orbitals of Na, Mg, Al, Si, P, S, and Cl. These parameters are for use in the application of the CNDO SCMO method to molecules containing second row atoms.

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Zusammenfassung Die Ionisierungspotentiale des Valenzzustands, I und die nicht-empirischen Ein-Zentren-Elektronen-Absto\ungsintegrale werden für die 3s-, 3p- und 3d-Orbitale von Na, Mg, Al, Si, P, S und Cl angegeben. Diese Parameter werden bei der Anwendung der CNDO-SCMO-Methode auf Moleküle, die Atome der zweiten Reihe enthalten, benötigt.

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Résumé On détermine les potentiels d'ionisation de l'état de valence I et les intégrales de répulsion monocentriques pour les orbitales 3s, 3p, 3d de Na, Mg, Al, Si, P, S et Cl. Ces paramètres sont utilisés dans l'application de la méthode CNDO SCMO à des molécules contenant des atomes de la seconde colonne.

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We thank the S.R.C. for a maintenance grant (to K.A.L.).     

The role of d orbitals in tetrahedral hybrid orbitals of oxy-ions

The hybrid orbitals of tetrahedral oxy-ions containing some d character have been calculated by maximum overlap method. The d characters of hybrid orbitals increase in the order of SiO, PO, SO, ClO, and decrease in order of GeO, AsO, SeO, BrO. The bond strengths are also obtained for these ions. The hybrid Orbital of VO, CrO, and MnO are of the type d³s as the result of calculation.     

Spherically symmetric axial Gaussian lobe 3d and 4f orbitals

The axial Gaussian lobe orbital (AGLO ) representations of 3d and 4f orbitals proposed by LeRouzo and Silvi have been angularly optimized to ensure spherical symmetry of filled 3d and 4f shells. The functions have been tested on the hydrogen atom in the presence of high quality s and p basis sets and found to provide excellent minimal Gaussian representations of polarization functions. Exact orbital degeneracy is not obtained within each shell, however. Tabulated values are given to allow arbitrary scaling of the 3d and 4f lobe mimic orbitals.     

The nature of sulfur bonding in thiopyrylium cation

Comparison of the PMR spectrum ofthiopyrylium cation with those of the oxygen (pyrylium cation) and nitrogen (pyridinium cation) analogs has suggested the unique electronic structure of the thiopyrylium cation. To investigate this structure the extended Hückel MO calculations have been carried out using two basis sets, one with and another without sulfur 3d orbitals. The electronic structure of thiopyrylium cation can be rationalized by the 3d orbital involvement of the S atom in the basis set. The primary effect of the involvement of 3d orbitals on the S atom is shown to be the electron transfer from the ring carbon fragment, in particular from the β ring carbons, to the S atom, with an accompanying increase in sulfur-α-carbon bond order.     

On the effect of d orbitals on relativistic bond-length contractions

5d AOs are found to diminish the usual relativistic bond-length contraction in some hydrides. This is shown to be a first-order effect, unrelated to the relativistic expansion of 5d AOs, by both the perturbative Dirac-Fock one-center expansion and Hartree-Fock-Slater methods. The latter method is used to investigate the chemical similarity of Zr and Hf.     

The generalized valence bond π orbitals of ethylene and allyl cation

Using a fixed sigma core obtained from full electron ab initio Hartree-Fock calculations, the spatially projected GVB orbitals for the pi electron systems of ethylene and allyl cation are reported. The GVB(SP) method generates wavefunctions possessing the correct spatial and spin symmetry without restricting the nature of the individual orbitals. The GVB(SP) wavefunction provides a simple interpretation of the molecule in terms of orbitals each containing a single electron. The resulting total energies and excitation energies agree very well with full configuration interaction calculations.     

The inclusion of 3d orbitals in hybrid obitals. A valence-bond study on NH3

Valence-bound calculations are reported for the ground state of NH₃ in which nitrogen 3d orbitals are used in the hybrid orbitals. Inclusion of 3d orbitals raises the value for the inversion barrier above the experimental value. The contribution of the N⁺ structure is decreased when 3d orbitals are included.     

An ab initio study of the effect of the 3d orbitals of phosphorus on the properties of the phosphate group

A large number of properties of the dimethylphosphate anion (DMP^?), model system for the phosphate group of the nucleic acids and the phospholipid components of membranes, has been investigated by the SCF ab initio procedure including the 3d orbitals of the phosphorus atom in the gaussian basis set and the results of the computations were compared with similar results obtained previously without taking these orbitals into account. The properties investigated include the conformational states of DMP with respect to the torsion about the P-O_ester bonds, the distribution of the electronic charges, the molecular electrostatic potentials generated by DMP^?, the characteristics of the molecular orbitals, particularly the electronic isodensity maps, the hydration scheme. Qualitatively, the introduction of the 3d orbitals modifies little the general aspects of the results obtained for most of the properties studied. On the quantitative level significant, although generally not great, modifications may be noticed with respect to some features of these properties. One of the strongest influences of the introduction of the 3d orbitals concerns the decrease of the net electronic charges in DMP^?.     

聚苯硫醚中硫原子3d轨道参与成键作用的研究

运用EHMO/CO计算方法,通过对聚苯硫醚在掺杂前后的体系能量和能带结构的研究,以及对聚苯硫醚中电荷分布和C-S键性质的分析,肯定了聚苯硫醚中硫原子的3d轨道参与了重要的成键作用。     

Role of core and valence atomic orbitals in the formation of chemical bonds

The general principles of the electronic structure of molecules and complexes are discussed. An analysis of photoelectron and x-ray photoelectron spectra reveals that in most cases, the interaction of the valence AO's results in the formation of delocalized MO's, which are populated by electrons, but are not bonding according to their energies (molecules with small atomic cores are exceptions). These MO's do not make a positive contribution to the exothermic effect of chemical bonding. The delocalization of the valence electrons in such MO's reduces their charge density in the region of the atomic cores and lowers the energy of the inner atoms-in-molecules levels as a result of the reduction of the internal shielding; the ESCA shifts of the inner electronic levels confirm this stabilization. In accordance with the virial theorem, the lowering of the energy of the core levels of the central atoms (with simultaneous, generally small changes in the energy of the core levels of the ligands and despite the significant destabilization of the delocalized MO's in comparison to the valence orbitals of the corresponding free atoms) makes up the main contribution to the energy of chemical bonds.This article is being published for purposes of discussion.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 5, pp. 572–578, September–October, 1986.     

Extension of MNDO to d orbitals: Parameters and results for the halogens

A recently proposed extension of the MNDO formalism to d orbitals has been parameterized for the halogens CI, Br, and I. Extensive test calculations indicate slight consistent improvements for normalvalent molecules and dramatic improvements for hypervalent molecules, in comparison with established MNDO -type methods without d orbitals. The mean absolute errors in calculated heats of formation are 3.9 kcal/mol for 155 normalvalent compounds and 2.8 kcal/mol for 23 hypervalent compounds. The predicted structures of the hypervalent molecules are qualitatively correct, with a mean absolute error of 2° in 19 bond angles.     

Automatic geometry optimization for molecules with d orbitals. I. General analytic formulas for derivatives of slater orbitals

General analytic formulas for derivatives of real Slater orbitals with respect to the Cartesian coordinates x and y have been derived. The application of this result to molecular geometry optimization or to the construction of a force constant matrix is briefly discussed.     

Vacant outer orbitals in oxy anions of silicon,phosphorus, sulfur,and chlorine

The ions MO₄ ^n–, where M = Si, P, S, and Cl, have been calculated by a nonempirical Hartree-Fock method with the inclusion of the vacant 3d and 4s AO's of the central atom in the basis set. The calculations have shown that an increase in the role of the vacant outer molecules in M-O chemical bonding occurs.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 26, No. 2, pp. 233–236, March–April, 1990.