Conformations of Organophosphine Oxides

Abstract

The conformations of a series of organophosphine oxides, OP(CH3)2R, where R = methyl, ethyl, isopropyl, tert-butyl, vinyl, and phenyl, are predicted using the MP2/cc-pVTZ level of theory. Comparison of potential energy surfaces for rotation about P-C bonds with crystal structure data reveals a strong correlation between predicted location and energetics of minima and histograms of dihedral angle distributions observed in the solid state. In addition, the most stable conformers are those that minimize the extent of steric repulsion between adjacent rotor substituents, and the torsional barriers tend to increase with the steric bulk of the rotating alkyl group. MM3 force field parameters were adjusted to fit the MP2 results, providing a fast and accurate model for predicting organophosphine oxides shapes-an essential part of understanding the chemistry of these compounds. The predictive power of the modified MM3 model was tested against MP2/ cc-pVTZ conformations for triethylphosphine oxide, OP(CH2CH3)3, and triphenylphosphine oxide, OP(Ph)3. Disciplines Chemistry CommentsReprinted (adapted) ABSTRACT: The conformations of a series of organophosphine oxides, OP(CH 3 ) 2 R, where R = methyl, ethyl, isopropyl, tert-butyl, vinyl, and phenyl, are predicted using the MP2/cc-pVTZ level of theory. Comparison of potential energy surfaces for rotation about P−C bonds with crystal structure data reveals a strong correlation between predicted location and energetics of minima and histograms of dihedral angle distributions observed in the solid state. In addition, the most stable conformers are those that minimize the extent of steric repulsion between adjacent rotor substituents, and the torsional barriers tend to increase with the steric bulk of the rotating alkyl group. MM3 force field parameters were adjusted to fit the MP2 results, providing a fast and accurate model for predicting organophosphine oxides shapesan essential part of understanding the chemistry of these compounds. The predictive power of the modified MM3 model was tested against MP2/cc-pVTZ conformations for triethylphosphine oxide, OP(CH 2 CH 3 ) 3 , and triphenylphosphine oxide, OP(Ph) 3 .

The Impact of Crystal Packing and Aurophilic Interactions on the Luminescence Properties in Polymorphs and Solvate of Aroylacetylide–Gold(I) Complexes

“…Last but not least, the conformations adopted by PEt 3 moieties are g+ag− in most of the structures (i.e., one ethyl moiety parallel to P−Au bond and two other in plane perpendicular to that bond and pointing in opposite directions; see the Supporting Information, Figures S7–S10), which was identified as the most common structure for triethylphosphine in the CSD and as the one preferred energetically for isolated phosphines . There are traces of another popular conformation, g+ag+, represented by minor conformers of disorder in the structures of complexes 1 and 2 ′.…”

“…However,t he remaining units in column Bs eem tilted out of chain with respect to what would have been in the structure of complex 1'- Figure 4. X-ray powder diffraction patterns:a)the powdered sample of deteriorated,bleachedcrystals of complex 1'-A,and the simulated powder patterns of b) complex 1'-B,c)complex 1'-C,and d) complex 1'-A.T he most prominentp eaks characteristic of complex 1'-A,specifically,(100) at 2q = 6.488,( 10-2) at 2q = 10.898,and (102) at 2q = 11.548,are completely missing, whichc onfirms phase transition,w hereas the mostp rominent peaks characteristicofc omplex 1'-B,specifically,(011),(200) at % 2q = 9.788, (21-1) at 2q = 13.348,(211), at % 2q = 14.488,and ,(420)a t % 2q = 25.008,are clearlyv isible in the experimental pattern.T hereare also no indications of the mostc haracteristic peaks of complex 1'-C,s pecifically, (100) at % 2q = 6.918, ,(01-3) at 2q = 9.648,(02-2) at % 2q = 11.798,and (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) at % 2q = 11.908.…”

“…Synthesis (Acetylide)gold(I) complexes 1-6 weres ynthesized by using a published method and startingf rom propynoylarenes 7-9 and 1-arylpenta-2,4-diyn-1-ones 10-12.C ompounds 7-9 were synthesized in three steps [13] from benzaldehydes 13-15,w hich reacted with lithium trimethylsilyl acetylide to give the corresponding propargyl alcohols [16][17][18].T hen, reaction with potassium carbonate in methanolf ollowed by oxidation with man-ganese(IV) oxide in acetoneg ave the desired propynoylarenes in good overall yields (Scheme 1).…”

“…Last but not least, the conformationsa dopted by PEt 3 moieties are g + agÀ in most of the structures (i.e.,o ne ethyl moiety parallel to PÀAu bond and two other in plane perpendicular to that bond and pointing in opposited irections;s ee the Supporting Information, Figures S7-S10), which was identified as the most commons tructure for triethylphosphine in the CSD [16] anda st he one preferred energeticallyf or isolated phosphines. [17] There are traces of another popular conformation, g + ag + ,r epresented by minor conformers of disorder in the structures of complexes 1 and 2'.I nt he structure 1'-B, however,b oth PEt 3 moieties adopt the less frequent and less energetically preferred conformations (g + ag + and g-aa). The presence of atypical conformations in this particularc ase results in the formation of an umber of stabilizing close CÀH···p contactsb etween the ethyl groups and the phenylr ings in the crystal lattice and in significantly higherc rystal density with respect to complex 1'-A solvate (1.93 vs. 1.75 gcm À3 ).…”

Lanthanide phosphine oxide complexes

“…Bond distances within phosphine oxides will affect the steric requirements of the ligands. Structural data showing an increase in the PO distance along the series Me 2 RPO (R = Me, Et, i Prop, t Bu) has been explained on the basis of molecular mechanics calculations as being due to increased steric repulsions and electronegativity effects which also increase the P-C(R) bond length [9].…”