1,720,990 research outputs found
On the electronic structures of metaphosphate PX(3)((-)) and metaphosphite PX(2)((-)) anions, X=CH2,SIH2,NH,PH,O,S
No full textSchoeller W, Strutwolf J. On the electronic structures of metaphosphate PX(3)((-)) and metaphosphite PX(2)((-)) anions, X=CH2,SIH2,NH,PH,O,S. PHOSPHORUS SULFUR AND SILICON AND THE RELATED ELEMENTS. 1996;111(1-4):673-673
Orbital isomerism in the 1.3-diphosphacyclobutane-2.4-diyl, quantum chemical investigations at MCSCF level
No full textSchoeller W, Strutwolf J, Niecke E. Orbital isomerism in the 1.3-diphosphacyclobutane-2.4-diyl, quantum chemical investigations at MCSCF level. PHOSPHORUS SULFUR AND SILICON AND THE RELATED ELEMENTS. 1996;111(1-4):674-674
Digital simulation of potential step experiments using the extrapolation method
No full textStrutwolf J, Schoeller W. Digital simulation of potential step experiments using the extrapolation method. ELECTROANALYSIS. 1997;9(18):1403-1408.For large values of the model diffusion coefficient the Crank-Nicolson scheme produces poor numerical results, if it is used for the simulation of a potential step experiment. On the other hand the Backward Euler or fully implicit scheme, not suffering from this drawback, is of lower accuracy. We apply the extrapolation method introduced by Morris et al. to the simulation of Cottrellian diffusion and to a simple catalytic mechanism. The extrapolation method, does not show the oscillating behavior of numerical solutions and is of higher accuracy than the fully implicit scheme. Comparison to other implicit difference schemes are presented. The extrapolation schemes show superior results for the diffusional problem and for the short time behavior of the catalytic mechanism
ON THE ELECTRONIC HYPERSURFACE OF THE METHYLENEPHOSPHENIUM CATION
No full textSchoeller W, STRUTWOLF J. ON THE ELECTRONIC HYPERSURFACE OF THE METHYLENEPHOSPHENIUM CATION. THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE. 1994;111:127-137.The electronic hypersurface of the methylenephosphenium cation is explored on the basis of ab initio calculations of double-zeta quality. The findings are compared with corresponding investigations on the nitrogen analogue (iminomethylene cation), methylenesilylene and methylenecarbene. For the phosphorus case, PCH2 is the most stable species on the potential energy surface, while for the nitrogen case the acetylenic structure, HNCH+ (C(infinity v) symmetry) is the most stable species. For the substituted cases a bridged geometry comes to the fore for PCHR+ (R = NH2, PH2, C6H5). These substituents strongly pronounce cation stability for PCHR+, as evaluated by corresponding group transfer reactions
PHOSPHORUS IN STRAINED RING-SYSTEMS
No full textSchoeller W, BUSCH T, HAUG W, STRUTWOLF J. PHOSPHORUS IN STRAINED RING-SYSTEMS. PHOSPHORUS SULFUR AND SILICON AND THE RELATED ELEMENTS. 1993;77(1-4):645-648.The effect of phosphorus substitution on the properties of strained cyclic systems is evaluated by means of quantum chemical claculations at an ab initio calculations at SCF and MCSCF level. Main emphasizes is directed to an investigation of bonding in the series of phosphacyclobutadienes (in comparison to azacyclobutadienes), cyclophosphenes and phosphacylopropenes
Linear and cyclic sweep voltammetry at a rotating disk electrode. A digital simulation
No full textStrutwolf J, Schoeller W. Linear and cyclic sweep voltammetry at a rotating disk electrode. A digital simulation. ELECTROANALYSIS. 1996;8(11):1034-1039.The transport equation for the rotating disk electrode is solved numerically with appropriate boundary conditions for reversible and nonreversible redox reactions. A comparison of the computational mode with experimentel data is presented. The adaption of a steady state under variations of experimental parameters upsilon (scan rate) and omega (angular frequency of rotation) is investigated. It is shown that a triangular voltage scan can be used to indicate the attainment of a steady state in every zone of the current-voltage curve
Cation and anion stabilities of low-coordinated π-bonded phosphorus systems. An ab initio quantum chemical investigation
No full textSchoeller W, Tubbesing U, Begeman C, Strutwolf J. Cation and anion stabilities of low-coordinated π-bonded phosphorus systems. An ab initio quantum chemical investigation. In: Phosphorus, Sulfur, and Silicon and the Related Elements. Phosphorus, Sulfur, and Silicon and the Related Elements. Vol 109. GORDON BREACH SCI PUBL LTD; 1996: 101-104.Quantum chemical calculations at RHF/6-3 1+g(d,p) with electron correlation (MP4SDTQ) corrections are reported on (a) a relative scale of model cations and anions derived from low-coordinated pi-bonded phosphorus, (b) on band structure calculations (tight-binding approximation:) of the P-iodine iminophosphane and (c) on lithiation to (unsolvated) corresponding structures derived from the anionic species
ON THE ELECTRONIC HYPERSURFACE OF THE PHOSPHIRANYL CATION - A THEORETICAL-STUDY
No full textSchoeller W, HAUG W, STRUTWOLF J. ON THE ELECTRONIC HYPERSURFACE OF THE PHOSPHIRANYL CATION - A THEORETICAL-STUDY. BULLETIN DE LA SOCIETE CHIMIQUE DE FRANCE. 1993;130(5):636-641.The bonding properties in the phosphiranyl cation are outlined in detail by ab initio quantum chemical investigations. This includes calculations on the electrocyclic reaction towards the 2-phosphaallyl cation and an investigation of the various structural isomers of the title compound. In contrast to the cyclopropyl cation, which easily ring-opens to the allyl cation, the phosphiranyl cation only reluctantly undergoes ring opening. This can be related to less strain in the phosphiranyl ring system in comparison with the cyclopropyl ring system. The matter is outlined using the corresponding homodesmic reactions
ROTATIONAL BARRIER IN PHOSPHATRIAFULVENE - AN MCSCF STUDY
No full textSchoeller W, STRUTWOLF J, HAUG W, BUSCH T. ROTATIONAL BARRIER IN PHOSPHATRIAFULVENE - AN MCSCF STUDY. JOURNAL OF COMPUTATIONAL CHEMISTRY. 1993;14(1):3-7.As probed by ab initio calculations at SCF and MCSCF levels, the rotational barrier of the PC double bond in the title compound is similar in magnitude to the corresponding one in methylenephosphane. The transition state for rotation is dipolaric in nature. On this basis, a combination of electron releasing and electron accepting substituents reduces the magnitude of the rotational barrier in phosphatriafulvene. It is supported by experimental investigations
ON THE ELECTRONIC-STRUCTURES OF THE METAPHOSPHATE (METAPHOSPHITE) ANIONS PX(3)((-))(PX(2)((-))), X=CH2, SIH2, NH, PH, O, S
No full textSchoeller W, STRUTWOLF J, NIECKE E. ON THE ELECTRONIC-STRUCTURES OF THE METAPHOSPHATE (METAPHOSPHITE) ANIONS PX(3)((-))(PX(2)((-))), X=CH2, SIH2, NH, PH, O, S. THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE. 1995;333(3):249-260.The structures of the metaphosphates (metaphosphites) PX(3)((-)))(PX(2)((-))), (X = CH2, SiH2, NH, PH, O, S) are investigated by means of ab initio calculations of double-zeta quality. For the cases X = CH2 and SiH2 a second-order Jahn-Teller distortion on the planar (D-3h) geometries is operative in the metaphosphate anions. It causes pyramidalization of the terminal groups (for X = CH2, SiH2) and the central phosphorus atom (for X = SiH2). The various types of symmetry distortions are accompanied by a weak alpha+pi bonding of the terminal ligands towards the central phosphorus atom. This matter is evidenced by an analysis of corresponding group transfer reactions. In contrast, for the cases X = NH, PH, O, S, planar structures (C-3h, D-3h) are adopted with formation of strong alpha+pi bonds of the central phosphorus towards the ligand atoms, again in accord with corresponding group transfer reactions. The vibrational analysis within the harmonic approximation reveals a decreasing tendency for pyramidalization at the central phosphorus atom, with increasing electronegativity of the ligand X. This is due to depletion of pi-electron density at the central atom. A silylene unit is more strongly bound in the tris(silylene))metaphosphate anion than in the silylene-phosphorane, according to corresponding group transfer reactions
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