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  • Ab initio calculations  (2)
  • 1,2-Bis(dimethylamino)-3,4,5-triphenyl-3,4,5-triphospha-1,2-diborolane  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    The Triphosphide (tBu3Si)2P3Na: Formation, X-ray and Ab initio Structure Analyses, Protonation and Oxidation to Triphosphane (tBu3Si)2P3H and Hexaphosphanes (tBu3Si)4P6⋆ (1998)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 833-841 
    Details
    ISSN: 1434-1948
    Keywords: Silicon ; Phosphorus ; Oligophosphides and -phosphanes ; NMR spectra ; X-ray structure analysis ; Ab initio calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The violet THF adduct (tBu3Si)2P3Na(THF)4 (1a) of the triphosphide (tBu3Si)2P3Na (1) is prepared, (i) by protolysis of the tetraphosphide (tBu3Si)2P4Na2 (2) with an equimolar amount of CF3CO2H in THF (transformation of 2 into 1), (ii) by the reaction of tBu3SiNa and the oligophosphane (tBu3SiP3)n in THF (building-down of Pn), and (iii) by the action of tBu3SiNa on PCl3 in THF (building-up of Pn). According to X-ray structural analysis, the SiPPPSi skeleton of the anionic part [tBu3SiPPPSitBu3]- of 1a is W-shaped with two P-P 11/2 bonds; in addition, 1a contains a planar deltoid P3Na backbone with the 4 THF molecules coordinated to Na. The protolysis of 1a leads to cyclotriphosphane (tBu3Si)2P3H (11), and the oxidation of 1a leads to 1,1′-bicyclotriphosphane (tBu3Si)2P3-P3(SitBu3)2 (12) as the main product and bicyclo[3.1.0]hexaphosphane (tBu3Si)4P6 (13) as an isomer of 12. The structures of 11, 12, and 13 as well as the structure of 1a have been unambiguously determined by 31P-NMR studies. Ab initio structure and energy calculations show that the acyclic P3H2- with allylic conjugation and P-P 11/2 bonds is thermodynamically more stable than the cyclic isomer whereas, in contrast, the neutral compound P3H3 prefers the cyclic form. The exceptional downfield shift of the NMR signal of the central phosphorus in 1a is in agreement with DFT NMR calculations for a model compound [H3SiPPPSiH3]Na with P-P 11/2 bonds.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Calculated Properties and Ring-Chain Rearrangements of Triphosphirane (P3H3) (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 103-112 
    Details
    ISSN: 1434-1948
    Keywords: Ab initio calculations ; Ionization potentials ; Phosphorus ; Heterocycles ; Small ring systems ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio quantum chemical calculations have been used to explore the P3H3 potential energy surface focussing on the ring-chain rearrangements of the three-membered ring in (PH)3 (1), the parent triphosphirane. Relative energies between stationary points were estimated using the QCISD(T)/6-311G(d,p) method based on MP2/6-31G(d,p) geometries and corrected for zero-point contributions. Ring strain, proton affinities, ionization and excitation energies and heats of formation have been evaluated using larger basis sets, e.g. 6-311++G(3df,2p). The cyclic trans-triphosphirane (1a) is the most stable P3H3 isomer and lies about 40 kJ/mol below the open-chain phosphanyldi-phosphene (H2P-P=PH). The decrease of ring strain in three-membered rings when CH2 is replaced by PH is confirmed. Triphosphirane 1a is a virtually strain-free ring and even gains some stabilization relative to three separate P-P single bonds. The reduced ring strain also helps diminish the phosphorus inversion barrier to 224 kJ/mol compared to the monocyclic isomers of (CH2)(PH)2 and (CH2)2(PH). Compound 1a follows a pure ring-opening or a 1,2-hydrogen shift rather than a combined motion pathway, in fundamental contrast with corresponding processes of diphosphirane and phosphirane. This is due to the existence of an open-chain P3H3 phosphorane intermediate stabilized by allylic conjugation. The pericyclic ring-opening of 1a is the most favored process but the energy barrier in the gas phase is about 180 kJ/mol high. Electron density is largely delocalized within the three-membered P3 ring not only in the C3v-symmetric 1b (all-cis) but also in 1a (Cs). The proton affinity of 1a is similar to that of PH3. The proton affinities decrease with n in cyclo-(CH3)3 -n(PH)n and their values were obtained: PA(1a) = 777 ±10, PA(diphosphirane) = 799 ±10 and PA(phosphirane) = 802 ±10 kJ/mol. Heats of formation are evaluated as follows (ΔH°f0 at 0 K in kJ/mol): 1a, 70 ±10; cyclo-(PH)2(PH2)+ (protonated 1a), 821 ±10; diphosphirane, 85 ±10; cyclo-(CH2)(PH)(PH2)+ (protonated diphosphirane), 814 ±10; phosphirane, 86 ±10; and protonated phosphirane, 812 ±10 kJ/mol. All P rings remain cyclic following ionization to the radical cations. Adiabatic ionization energies (IEa) are estimated as: 1a and diphosphirane, 9.3 ±0.3 eV and phosphirane 9.5 ±0.3 eV. The first UV absorption band shifts toward the longer wavelength region on going from phosphirane to 1a. The GIAO/B3LYP computed magnetic shieldings for 1a and related molecules reveal a clear relationship between the narrow bond angles in the rings and their unusually strong magnetic shielding. The similarity of the predicted 31P-NMR signals in 1a and its heteroanalog diphosphirane, (CH2)(PH)2, can be rationalized in terms of a compensation of the carbon-substituent effect (downfield shift) and the bond-bending effect imposed by the ring (upfield shift).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    1,2-Bis(dimethylamino)-3,4,5-triphenyl-3,4,5-triphospha-1,2-diborolan und 1,2-Bis(dimethylamino)-3,4,5,6-tetra-tbutyl-3,4,5,6-tetraphospha-1,2-diborin: Synthese und Struktur sowie Berechnungen zur MolekülstrukturProfessor Hans-Georg von Schnering zum 65. Geburtstage gewidmet (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 1462-1470 
    Details
    ISSN: 0044-2313
    Keywords: 1,2-Bis(dimethylamino)-3,4,5-triphenyl-3,4,5-triphospha-1,2-diborolane ; 1,2-bis(dimethylamino)-3,4,5,6-tetra-tbutyl-3,4,5,6-tetraphospha-1,2-diborine ; preparation ; NMR ; molecular structures ; ab initio calculations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,2-Bis(dimethylamino)-3,4,5-triphenyl-3,4,5-triphospha-1,2-diborolane and 1,2-Bis(dimethylamino)-3,4,5,6-tetra-tbutyl-3,4,5,6-tetraphospha-1,2-diborine: Synthesis and Structure as well as Calculations on the Molecular StructureThe diphosphides K2[(C6H5)P—(C6H5)P—P(C6H5)], 4 or K2[(tBuP)—(tBuP)2—P(tBu)], 5, react with (ClBNMe2)2 to form the binary 5-membered ring system 1,2-bis(dimethylamino)-3,4,5-triphenyl-3,4,5-triphospha-1,2-diborolane (C6H5P)3(BNMe2)2, 2a, and the 6-membered ring system 1,2-bis(dimethylamino)-3,4,5,6-tetra-tbutyl-3,4,5,6-tetraphospha-1,2-diborine, (tBuP)4(BNMe2)2, 3a, respectively. 2a and 3a could be obtained in a pure form and characterized NMR spectroscopically and by X-ray structure analyses. The two ring systems are folded; 2a exists in the „envelope“- 3a in the „boat“-conformation. Ab initio computations for 3,4,5-triphospha-1,2-diborolane M5 show that the global minimum is characterized by one B—P double bond. The parent compound geometry M6 is characterized by transannular bonding in the PH—BH—BH—PH moiety which differs in character from those in the four- and five-membered rings (BH)2(PH)2 and (BH)2(PH)3 M5 d, respectively. Explicit calculation of the influence of amino substituents on boron improved agreement of the bond length between computed and X-ray data.
    Notes: Die Diphosphide K2[(C6H5)P—(C6H5)P—P (C6H5)], 4, bzw. K2[(tBuP)—(tBuP)2—P(tBu)], 5, reagieren mit (ClBNMe2)2 zu dem binären Fünfringsystem 1,2-Bis(dimethylamino)-3,4,5-triphenyl-3,4,5-triphospha-1,2-diborolan (C6H5P)3(BNMe2)2, 2a, bzw. dem Sechsringsystem 1,2-Bis(dimethylamino)-3,4,5,6-tetra-tbutyl-3,4,5,6-tetraphospha-1,2-diborin, (tBuP)4(BNMe2)2, 3a. 2a und 3a konnten in reiner Form isoliert, NMR-spektroskopisch und durch Röntgenstrukturanalysen charakterisiert werden. Beide Ringsysteme sind gefaltet; 2a zeigt eine „envelope“- 3a eine „Wannen“-Konformation.Ab initio Berechnungen an 3,4,5-Triphospha-1,2-diborolan M5 zeigen, daß im globalen Minimum eine B—P-Doppelbindung mit annähernd planarem σ3-Phosphor vorliegt. Die Geometrie der Stammverbindung des Sechsringes M6 weist „durch-den-Ring“-Bindung in der PH—BH—BH—PH-Baugruppe auf, welche sich von jenen im Vier- und Fünfring M5 d unterscheidet. Durch die explizite Berechnung des Einflusses von Aminosubstituenten an Bor auf die Geometrien des Fünf- und Sechsringes verbessert sich die Übereinstimmung der Bindungslängen mit den Daten der Röntgenstrukturanalyse.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966220906
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