Hartree−Fock and Møller−Plesset (MP2) Treatment of Oxygen-Containing Phosphorus Compounds

Stewart, Eugene L.; Nevins, Neysa; Allinger, and Norman L.; Bowen, J. Phillip

doi:10.1021/jo961212a

Cited by 19 publications

(18 citation statements)

References 23 publications

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“…The gas phase values from our simulations are very close to those of the second-order Møller-Plesset perturbation theory (MP2) at 0 K. 22) In particular, each molecule has a well-defined double bond (P=O) and three single bonds (P-O) in both calculations. Unfortunately, no experimental values are available for the gas phase.…”

Section: Resultssupporting

confidence: 72%

“…1,2) Moreover, in spite of its high viscosity, liquid phosphoric acid has high proton conductivity, which makes it useful as fuel cell electrolytes. Therefore, many experimental and theoretical studies have been carried out on the liquid phase [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] as well as on the monomer [21][22][23] ( Fig. 1), crystal, [24][25][26] and the polymeric gels [27][28][29][30] of phosphoric acid.…”

Section: Introductionmentioning

confidence: 99%

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Ab InitioMolecular-Dynamics Simulation of Concentrated Phosphoric Acid

Tsuchida

2006

J. Phys. Soc. Jpn.

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We have investigated the properties of 100% phosphoric acid (H 3 PO 4 ) in the liquid state by the combination of gradient-corrected density-functional theory and norm-conserving pseudopotentials. Various structural properties as well as the vibrational density of states have been calculated through molecular-dynamics simulations under the Born-Oppenheimer approximation. Proton transfer is found to occur frequently between adjacent PO 4 groups along the OH···O hydrogen bonds, which makes the single and double bonds indistinguishable.

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Section: Resultssupporting

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Ab InitioMolecular-Dynamics Simulation of Concentrated Phosphoric Acid

Tsuchida

2006

J. Phys. Soc. Jpn.

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“…13 Finally, ab initio calculations at the HF/6-31G** level led to the identification of two stable conformers, one with C 3 symmetry and all methoxy groups in gauche orientations, the other with C 1 symmetry, two MeO groups in gauche and the third in an anti orientation. 14 Structure optimisation at the MP2/6-31G** level indicated that the C 1 conformer was the more stable by about 18 kJ mol Ϫ1 . 14…”

Section: Introductionmentioning

confidence: 98%

“…Structure parameters a of F 2 POMe determined by microwave (MW) spectroscopy,14 gas electron diffraction (GED)15 and density functional theory (DFT) calculations at the B3PW91/6-311ϩG* level…”

mentioning

confidence: 99%

Molecular structure and conformational preferences of trimethylphosphite, P(OCH3)3, as a free molecule and as a ligand in d-block metal complexesDedicated to Professor L. V. Vilkov, Moscow State University, on the occasion of his 70th birthday.

Belyakov¹,

Dalhus²,

Haaland³

et al. 2002

J. Chem. Soc., Dalton Trans.

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Free P(OCH 3 ) 3 has been studied by gas electron diffraction (GED) and DFT calculations at the B3PW91/ 6-311ϩG* level. Each conformer is characterised by three dihedral angles τ(COPlp) where lp denotes the direction of the electron lone pair on the P atom; assumed to lie in a plane containing the P-O bond and bisecting the opposing OPO angle. DFT calculations indicate that the most stable conformer is an anti,gauche ϩ , gauche ϩ (ag ϩ g ϩ ) conformer characterised by the angles τ a = (COPlp) Ϫ173, τ b = 54 and τ c = 41Њ. It is followed by an ag Ϫ g ϩ conformer at ∆E = 6.3 kJ mol Ϫ1 , an aa ϩ g ϩ conformer at ∆E = 6.6 kJ mol Ϫ1 , and a g ϩ g ϩ g ϩ conformer at ∆E = 10.4 kJ mol Ϫ1 . The calculated standard free energies at 298.15 K indicate that the mole fractions in the gas phase at this temperature are χ(±ag ϩ g ϩ ) = 73%, χ(ag Ϫ g ϩ ) = 16%, χ(±aa ϩ g ϩ ) = 10% and χ(±ag ϩ g ϩ g ϩ ) =1%; GED data indicate that the mole fractions of the more stable conformers at room temperature are χ(±ag ϩ g ϩ ) = 78(13)%, χ(ag Ϫ g ϩ ) = 9(11)% and χ(±aa ϩ g ϩ ) = 14(21)%. Natural Bond Orbital (NBO) analysis of the wavefunctions suggest that while bond distances and valence angles are determined by anomeric effects, the relative stabilities of the four conformers are not determined by such effects alone. Examination of the crystal structures of 287 complexes where one or more P(OCH 3 ) 3 units are coordinated to a d-block transition metal M, shows that in the 523 crystallographically independent MP(OCH 3 ) 3 fragments 46% of the trimethylphosphite units adopt a ±ag ϩ g ϩ conformation, 19% an ag Ϫ g ϩ conformation and 30% a ±aa ϩ g ϩ conformation. It is suggested that the increased number of ±aa ϩ g ϩ conformers and decreased number of ±ag ϩ g ϩ conformers relative to the gas phase, as well as the folding back of the gauche ligands are due to interligand repulsion in the transition metal complexes. Structure optimisation of F 2 POMe by DFT calculations at the B3PW91/6-311ϩG* level indicate that the most stable conformation is anti, while the energy of a gauche conformer is about 15 kJ mol Ϫ1 higher. NBO analysis of the wavefunctions indicate that the relative stabilities of the two conformers as well as the differences between bond distances and valence angles may be determined by anomeric effects.

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“…They used semi-empirical methods to deduce the likely lowest energy conformation in both the free and complexed form. Their conclusions were that a conformation with values of t 1-3 equal to 0, 0 and 180 • (near to but not C) was the lowest energy conformation for free trimethyl phosphite, followed by D, and that complexation of trimethyl phosphite switched the preferred conformation to F, followed by C. Later, ab initio calculations by Stewart et al suggested the presence of two major isomers of free trimethyl phosphite (B and C according to the notation used in the present work), 21 and that C is the lower in energy by about 4.2 kcal mol -1 (17.4 kJ mol -1 ). More recently, Belyakov et al have studied trimethyl phosphite by gasphase electron diffraction and by DFT methods, using the DFT geometries to estimate the fraction of the different conformers present in the gas phase.…”

Section: Introductionmentioning

confidence: 54%

Conformational analysis of PEt3 and P(OMe)3 in metal complexes

Ellis

Haddow²,

Orpen³

et al. 2009

Dalton Trans.

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The conformations of the archetypal acyclic phosphorus ligands PEt(3) and P(OMe)(3) are classified on the basis of the observation that torsions about the P-C (or P-O) bonds show favoured conformations lying close to gauche (+/-60 degrees) or anti values (180 degrees). Analysis of the symmetry of the conformation space defined by the three M-P-X-C (X = CH(2) or O) torsion angles (t(1-3)) implies the existence of seven unique conformer types (A (aaa), B (g(+)g(+)g(+)), C (ag(+)g(+)), D (aag(+)), E (g(-)ag(+)), F (ag(-)g(+)), G (g(-)g(+)g(+)) and their symmetry equivalents) arising from the combinations of g(-), g(+) and a torsions. These conformers are observed in 1972 M-PEt(3) and 735 M-P(OMe)(3) fragments from crystal structures of metal complexes in the CSD following the popularity sequence: F > C >> D > B > G > E >> A for M-PEt(3); and: C > D > F >> E >> A, B, G. for M-P(OMe)(3). Pathways for low-energy interconversion of these conformers, dominated by single chain flip routes, are readily inferred for M-P(OMe)(3). The conformers of M-PEt(3) are apparently less readily interconverted. The popularity of conformations is only loosely related to the energies of these conformations as calculated by DFT or MM methods for two-, four- (square planar) and six-coordinate metal complexes of these ligands (and free PEt(3) and P(OMe)(3)). It would appear that the conformational preferences observed are determined by a balance between intra-ligand effects (repulsion between chains and avoidance of syn-pentane-like); inter-ligand effects (repulsions between gauche substituents at P and cis co-ligands notably when the coordination number at the metal is high); and residual anomeric effects (weakly favouring anti conformations in P(OMe)(3) species).

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Hartree−Fock and Møller−Plesset (MP2) Treatment of Oxygen-Containing Phosphorus Compounds

Cited by 19 publications

References 23 publications

Ab InitioMolecular-Dynamics Simulation of Concentrated Phosphoric Acid

Ab InitioMolecular-Dynamics Simulation of Concentrated Phosphoric Acid

Molecular structure and conformational preferences of trimethylphosphite, P(OCH3)3, as a free molecule and as a ligand in d-block metal complexesDedicated to Professor L. V. Vilkov, Moscow State University, on the occasion of his 70th birthday.

Conformational analysis of PEt3 and P(OMe)3 in metal complexes

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