Quantum-chemical calculations of NMR chemical shifts of organic molecules: I. Phosphines,phosphine oxides,and phosphine sulfides

The accuracy in the calculation of ³¹P NMR chemical shifts in the series of the simplest phosphines, phosphine oxides, and phosphine sulfides was estimated in terms of the Hartree-Fock self-consistent final perturbation theory and density functional theory with different basis sets. The best agreement between the calculated and experimental data was achieved at the DFT/B3LYP/IGLO-III level of theory.     

Quantum chemical calculations of NMR chemical shifts of organic molecules: XI. Conformational and relativistic effects on the 31P and 77Se chemical shifts of phosphine selenides

Conformational and relativistic effects on the ³¹P and ⁷⁷Se chemical shifts of phosphine selenides were analyzed in terms of the ZORA-GIAO-B1PW91/TZP approach. The effect of conformation of phosphine selenides related to internal rotation about the single P-C bonds was found to be insignificant, while the contribution of relativistic spin-orbit interaction to the calculated values of ⁷⁷Se chemical shifts did not exceed 10 ppm. On the other hand, relativistic effects arising from magnetic shielding of the phosphorus nucleus in the P=Se fragment by selenium are fairly strong (25–30 ppm), which indicates the necessity of including the contribution of relativistic spin-orbit interaction in the calculation of ³¹P chemical shifts in phosphine selenides.     

Carbon-13 n.m.r. of the 8-phosphabicyclo[3.2.1]octane system

¹³C Chemical shifts and ¹³C? ³¹P nuclear spin coupling constants have been determined for 26 8-phosphabicyclo[3.2.1]octane derivatives, namely phosphines, phosphine oxides, phosphine sulphides and one phosphonium salt. The influence of the phosphorus configuration on δ and ²J(PC) values was examined and other factors influencing the ²J(PC) coupling constant are discussed.     

Theoretical calculations of nuclear spin coupling of phosphorus to carbon and hydrogen by the finite perturbation method

Finite perturbation calculations using CNDO/2 wave functions are presented for the determination of ³¹P? ¹³C and ³¹P? ¹H couplings. The calculations were carried out on 46 molecules and a comparison with experimental values is given. The groups of compounds considered were phosphonium cations, phosphine oxides, alkylidenephosphoranes, phosphine sulfides, phosphoranes and phosphines. With the exception of phosphines, the finite perturbation approach reproduces the experimental couplings with fair accuracy. It is found that there is a good correlation with the calculated ¹J(P, C) and the phosphorus 3s-carbon 2s bond orders for tetra- and pentavalent phosphorus compounds. This lends support to the growing body of evidence for the direct relationship of the magnitude of ¹J(P, C) and percent s character in the hybrid orbital on the carbon comprising the P? C bond. The finite perturbation technique was also used to explore the effects of geometrical changes on P? C and P? H couplings. Finally, the effect of deleting d orbitals on phosphorus is discussed briefly.     

Steric effects in 31P NMR spectra: ‘Gamma’ shielding in aliphatic phosphorus compounds

An examination of published ³¹P NMR spectral data for aliphatic phosphorus compounds has revealed that chain lengthening and branching effects on the chemical shift can be interpreted in terms similar to those used for ¹³C and ¹⁵N shifts. For six families of phosphorus compounds, a β-carbon substituent was shown to deshield phosphorus, while a γ-carbon caused shielding. The effects are additive, and good agreement was obtained between ³¹P shifts calculated with the appropriate constants and the experimental values. Shielding by γ-carbon is indicative of the operation of a steric influence on ³¹P chemical shifts, not heretofore articulated. The γ-effect is also useful in explaining the unusually large shielding found in six-membered cyclic phosphines.     

SYNTHESIS AND 31P NMR STUDY OF DIHYDRONAPHTHALENO- AND NAPHTHALENO-DERIVATIVES OF PHOSPHOLENE OXIDES

Abstract

Naphthalenophospholenes (dihydrobenzo[e] and [g]-phosphindoles) represent a new heterocyclic type that forms in 65-80% yield on dehydrogenation with Pd–C of the corresponding dihydronaphthaleno derivatives. The latter are readily accessible from hydrolysis of cycloadducts of certain vinyldihydronaphthalenes with P(III) chlorides. Six members of this family, as well as some derived phosphines and phosphonium salts, have been prepared. A phenanthrenophospholene oxide, also a new system, was synthesized similarly. ³¹P nmr chemical shifts were appreciably (5-10 ppm) upfield in aromatized phosphine oxides relative to the dihydro forms. It is proposed that this shift results more from a change in the steric environment about phosphorus, as the carbon beta- to it in the adjacent ring changes from tetrahedral to planar geometry, rather than from a change in the degree of interaction of a carbon p-orbital with phosphorus. The upfield shift was even more pronounced (13 ppm) for a phosphine. Most of the new compounds were characterized also by ¹³C nmr spectroscopy.     

1-Phosphabicyclo[3,3,1]nonan

1-Phosphabicyclo[3,3,1]nonane The synthesis of 1-phosphabicyclo[3,3,1]nonane II by free-radical cyclization of the primary phosphine (CH₂?CH? CH₂)₂CH? CH? PH₂ I is described. IR data favour a twin-chair conformation of II and its derivatives with oxygen V and sulphur VI . The magnitudes of the ³¹P NMR chemical shifts and of the phosphorus-hydrogen spin-spin coupling constants (¹J_PH, ²J_PH) are compared with values of aliphatic phosphines R₃P. The degree of substitution of CO from Ni(CO)₄ by II and other chemical evidences suggest a TOLMAN ligand cone angle of about 120–125°.     

NMR studies of dynamic behavior of dialkyl(acetylacetonato)bis(tertiary phosphine)cobalt(III) and related complexes in solution

The ¹H, ³¹P and ¹³C NMR spectra of cis-dialkyl(acetylacetonato)bis(tertiary phosphine)cobalt(III) complexes were obtained in several solvents. These complexes have an octahedral configuration with trans tertiary phosphine ligands. The coordinated tertiary phosphine ligands are partly dissociated in solution. One of the phosphine ligands in CoR₂(acac)(PR₃′)₂ can be readily displaced with pyridine bases to give pyridine-coordinated complexes. From observation of the ¹H and ³¹P NMR spectra several kinetic and thermodynamic data for exchange reactions and displacement reactions of tertiary phosphines were obtained.     

Organische Phosphorverbindungen XXVI. Phosphor-31 chemische Verschiebungen in primären Phosphinen

An empirical equation is given which allows the calculation of the ³¹P-chemical shifts of primary phosphines.     

Towards the versatile DFT and MP2 computational schemes for 31P NMR chemical shifts taking into account relativistic corrections

The main factors affecting the accuracy and computational cost of the calculation of ³¹P NMR chemical shifts in the representative series of organophosphorous compounds are examined at the density functional theory (DFT) and second‐order Møller–Plesset perturbation theory (MP2) levels. At the DFT level, the best functionals for the calculation of ³¹P NMR chemical shifts are those of Keal and Tozer, KT2 and KT3. Both at the DFT and MP2 levels, the most reliable basis sets are those of Jensen, pcS‐2 or larger, and those of Pople, 6‐311G(d,p) or larger. The reliable basis sets of Dunning's family are those of at least penta‐zeta quality that precludes their practical consideration. An encouraging finding is that basically, the locally dense basis set approach resulting in a dramatic decrease in computational cost is justified in the calculation of ³¹P NMR chemical shifts within the 1–2‐ppm error. Relativistic corrections to ³¹P NMR absolute shielding constants are of major importance reaching about 20–30 ppm (ca 7%) improving (not worsening!) the agreement of calculation with experiment. Further better agreement with the experiment by 1–2 ppm can be obtained by taking into account solvent effects within the integral equation formalism polarizable continuum model solvation scheme. We recommend the GIAO‐DFT‐KT2/pcS‐3//pcS‐2 scheme with relativistic corrections and solvent effects taken into account as the most versatile computational scheme for the calculation of ³¹P NMR chemical shifts characterized by a mean absolute error of ca 9 ppm in the range of 550 ppm. Copyright © 2014 John Wiley & Sons, Ltd.     

ON THE PHOSPHORUS-31 CHEMICAL SHIFTS OF SUBSTITUTED TRIARYLPHOSPHINES

Abstract

The ³¹P chemical shifts of eleven (4-ZC₆H₄)₃P compounds show a slight correlation with the Hammet [sgrave]para constant of Z. The unusually large upfield chemical shifts of (2-ZC₆H₄)₃P compounds are attributed to an extreme “gamma” effect caused by the restricted conformations due to the steric influence of the ortho substituents. Chemical shifts are given for about thirty triarylphosphines, and group contributions to phosphine chemical shifts are listed for twenty-one aryl groups.     

Conformational analysis and stereochemical dependences of 31P–1H spin–spin coupling constants of bis(2‐phenethyl)vinylphosphine and related phosphine chalcogenides

Theoretical energy‐based conformational analysis of bis(2‐phenethyl)vinylphosphine and related phosphine oxide, sulfide and selenide synthesized from available secondary phosphine chalcogenides and vinyl sulfoxides is performed at the MP2/6‐311G** level to study stereochemical behavior of their ³¹P–¹H spin–spin coupling constants measured experimentally and calculated at different levels of theory. All four title compounds are shown to exist in the equilibrium mixture of two conformers: major planar s‐cis and minor orthogonal ones, while ³¹P–¹ H spin–spin coupling constants under study are found to demonstrate marked stereochemical dependences with respect to the geometry of the coupling pathways, and to the internal rotation of the vinyl group around the P(X)‐C bonds (X = LP, O, S and Se), opening a new guide in the conformational studies of unsaturated phosphines and phosphine chalcogenides. Copyright © 2009 John Wiley & Sons, Ltd.     

Untersuchungen der kernmagnetischen Resonanz von Phosphorverbindungen. XXXI. Spin-Spin-Kopplungskonstanten in Phosphin- und Phosphit-Komplexen von Quecksilber (II), Cadmium und Zinn

NMR Studies of Phosphorus Compounds. XXXI. Spin-Spin Coupling Constants in Phosphine and Phosphite Complexes of Mercury(II), Cadmium, and Tin The ¹⁹⁹Hg? ³¹P spin spin coupling constants and the chemical shifts δ_P for 20 mercury(II) complexes with triorganyl phosphines and phosphites as ligands are reported. The effect of the ligand electronegativity on coupling constant and chemical shift is more clearly evident than in the corresponding platinum(II)-complexes. Furthermore corresponding data for some cadmium and tin complexes are tabulated.     

Acyl- und Alkylidenphosphane. XVII. Triacetylphosphan aus Tris(trimethylsilyl)phosphan

Acyl- and Alkylidenephosphines. XVII. Triacetylphosphine from Tris(trimethylsilyl)-phosphine Tris(trimethylsilyl)phosphine reacts at 0°C with excess acetyl chloride in cyclopentane to form chlorotrimethylsilane and triacetylphosphine 3a . In contrast to the corresponding 2,2-dimethylpropionyl derivate (Z)- 5b the intermediate compounds (E)- and (Z)-acetyl-[1-(trimethylsiloxy)ethylidene]phosphine 5a are thermally instable. They could not be isolated in a pure state, but were characterized by NMR spectroscopic methods only. The isomers differ scarcely in their chemical shift values, but very much in their coupling constants. If the solution is cooled unsufficiently diacetyl-[1-(trimethylsiloxy)vinyl]phosphine 7 and the keto-enol-tautomers of diacetylphosphine K-/E- 2a are formed to a greater extend. ¹H-{³¹P}-INDOR experiments allowed the correlation between ¹H- and ³¹P-NMR resonances and hence the correct identification of the phosphines formed. Within days the compounds 2a and 7 also react at +20°C with an excess of acyl halide to give triacetylphosphine 3a .     

Nuclear magnetic resonance of phosphorus compounds: 9—The NMR spectra of phosphirane

The 100 MHz proton and 40.4 MHz ³¹P NMR spectra of phosphirane (1) have been recorded at ?20 °C and analysed iteratively to yield coupling constants and chemical shifts. The 22.6 MHz ¹³C spectrum of 1 was recorded at 0 °C and analyzed. The ³¹P chemical shift of 1 was measured as 40 467 515.97 ± 0.08 Hz relative to TMS as 100 000 000.00 Hz. The geminal P-C-H couplings in 1 are opposite in sign and of different magnitudes (+16.14 and ?2.64 Hz); the P? H coupling (+158.34 Hz) is smaller than that in any other organic phosphine. These observations are discussed and correlated with the geometry of 1. The electronic structure of the strained ring of 1 is discussed in terms of a localized valence bond approach.     

First 1-phospha-1,3-dienes unsubstituted in the carbon chain by pyrolysis of diallylphosphines: A novel route to the phosphorus—carbon double bond

Allylic phosphine systems were studied as phosphorus–carbon double bond precursors. 1-Phenyl and 1-butyl-1-phospha-1,3-dienes were generated by pyrolysis at 350–460°C of the corresponding diallyl phosphines in a stirred-flow reactor. The unsubstituted phosphadienes generated in this manner dimerized; the formation of [4 + 2] cycloaddition products was confirmed by NMR and mass spectroscopic analysis. ³¹P NMR data of the 1-phospha-1,3-dienes were obtained.     

Quantum-chemical calculations of chemical shifts in NMR spectra of organic molecules: V. Stereochemical structure of unsaturated phosphonic acids dichlorides from 31P NMR spectral data

The stereochemical structure of unsaturated phosphonic acids dichlorides containing fragments C=C-POCl₂ and C=N-POCl₂ was investigated by ³¹P NMR spectroscopy and quantum chemistry. Starting from the experimental measurement and theoretical calculation of ³¹P NMR chemical shifts configurations were assigned and the conformational composition of compounds under study was determined.     

Assay of reducing sugars in beverages, wines, honey and marmalades using potentiometric stripping analysis (PSA)

Summary A simple, rapid and non-destructive method for the detection and determination of phosphines and phosphine oxides in solution by ¹H and ³¹P NMR spectroscopy is proposed. Diphenylphosphine (DPP) and diphenylphosphine oxide (DPPO) mixtures in C₆D₆ chosen as model system were studied in wide ranges of concentration (10^–2 to 4 mol/l). The detection of DPP and DPPO in solution by ¹H NMR was based on the presence of two doublets (hydrogen directly bonded to phosphorus, H_P) originating from P-H and P(O)H groups with one bond coupling constant ¹J_PH of 216.08 and 476.12 Hz. ³¹P NMR signals at –40.07 and +18.26 ppm additionally proved the presence of DPP and DPPO in solution. A linear dependence of the measured H_P and ortho-proton integral intensity on the concentration of DPP and DPPO was found. The content of DPP and DPPO evaluated by ³¹P without adding Cr(acac)₃ and by ¹H NMR agreed with the quoted amounts within 1 to 3%.Under Indo-Polish cultural exchange programme, temporarily at Silesian University