Phosphorus theoretical studies

Spectroscopic, and Theoretical Studies on MoleculEu- Phosphorus Oxides and Oxide Sulfides J. Clade, F. Frick, and M. Jansen... 

Adding a transition metal group to the phosphinidene in a q -fashion gives singlet species that are more palatable for use in chemical syntheses. Theoretical studies substantiated their preferred singlet nature, the extent of which depends on the substituent on phosphorus. When the transition metal group is M(CO)n... 

As in previous volumes, the abbreviations P" , P, P etc. refer to the co-ordination number of phosphorus. Where convenient the compounds in each section are dealt with in this order. A number of theoretical studies such as MO calculations are briefly discussed. They are placed in the sections where they are of most relevance. 

Trzcinskabancroft, B., Knachel, H., Dudis, D., Delord, T.J. and Marler, D.O. (1985) Experimental And Theoretical-Studies Of Dinudear Gold(I) And Gold(II) Phosphorus Ylide Complexes - Oxidative Addition, Halide Exchange, And Structural-Properties Including The Crystal And Molecular-Structures Of [Au (CH2)2PPh2]2 And [Au(CH2)2PPh2]2(CH3) Bri. Journal of the American Chemical Society, 107(24), 6908-6915. 

The number of theoretical studies involving phosphorus compounds and their reactions has grown sufficiently to warrant a separate section this year. This now forms section 1 of this chapter. Theoretical studies relating to specific physical methods will be found in the appropiate section as usual. 

A number of A5 n3 compounds (18) have chemical shifts in the range 127 to 178.37 A theoretical study supports the suggestion made in the last volume that these compounds are represented as phosphonium ylides with the negative charge distributed between the two sp carbon atoms bound to the phosphorus atom.3 ... 

As discussed in Section II. A, theoretical studies predicted that phospha-silenes with silyl substituents attached to phosphorus should have planar, trigonally coordinated silicon, with the Si—P w-bonds strengthened by the hyperconjugative influence of the silyl group.16 Recently, this was proved by a single-crystal X-ray structure determination of the derivative... 

This result has been further substantiated by the work of Koppel et al. <2001PCA9575>. They conducted a theoretical study of the basicity of phosphorus imines and ylides. Verkade bases 6-8 were included. They showed basicities comparable to commercially used organic superbases (/-BUP4 phosphazene imine), with compound 8 in particular giving calculated basicities similar to Li3P and Li20. 

The X-ray structure of 9 shows an unusual planar pentalene-type molecule with T-shaped bonding at phosphorus, rather than the more-expected pyramidal-type structure. This led Minyaev and co-workers <2001RCB195> to conduct a theoretical study of why this should be the case. They extended their results to include N and As... 

We theoretically studied the reactions of stable West silylenes 32 and 73 with phosphorus ylide H2C=PMe3.74 Similarly to the simplest analogs of carbenes, these compounds can form betaines in which the negative charge is localized on the silicon atom and the positive charge is localized on the phosphorus atom. These betaines can thermally decompose to form silenes (direction A, Scheme 39) or be isomerized to ylides via direction B. 

A theoretical study on the structures, magnetical properties, and energetics of phosphorus analogues of borazine, E2G3H6 191 (E = B, Al, Ga G = N, P, As), compared to those of other borazine analogues, E3J3H3 192 (J = O, S, Se) and to phosphazene (194),234 shows that results could vary with function of the reference system. Some compounds with P and As heteroatoms were found to prefer nonplanar geometries (Scheme 74). Contradictory results were... 

The most recent theoretical study, by Alhrichs and co-workers, deals with the di(phosphino)carbene Id and (phosphino) (phosphonio)carbenes Ie,f.16 The optimized geometry of the di(phosphino)carbene Id is weakly bent (PCP angle 160.5°) and highly unsymmetrical Only one of the phosphorus centers (P1) is in a planar environment, and it is much more closely bonded to the carbenic center than the other one (P1C 1.533 and P2C 1.765 A). The atomic charges (P1 +1.0, C -0.8, P2 +0.6) indicate that the short P bond is a double bond reinforced by Coulombic attraction, while the nature of the molecular orbitals revealed a slight delocalization of the carbene lone pair into the low-lying a (P-N) orbitals of the two phosphino substituents. The distortion from the symmetrical structure can be viewed as a second-order Jahn-Teller effect. 

Y Kiso, M Kobayashi, Y Kitaoka, K Kawamoto, J Takada. A theoretical study on the zone mobility-pH curve in paper electrophoresis of low-molecular-weight compounds with a dissociable proton and its application to phosphorus compounds. J. Chromatogr. 36 215-228 (1968). 

Spectroscopic, and Theoretical Studies on Molecular Phosphorus Oxides and Oxide Sulfides... 

All theoretical studies that include polarization function in the basis set of small unsubstituted ylides find a pyramidal ylidic carbon and a distorted tetrahedral phosphorus atom. Population analyses conclude that the charge distribution is P+ — C. ... 

Evidence has been provided604 for intramolecular nucleophilic catalysis by the carbonyl group during methanolysis of o- and / -formylbenzenesulfonates in basic media (see Scheme 121). A theoretical study of the zwittazido cleavage of 4-azido-2-pyrrolinones has been undertaken,605 and ab initio calculations have been carried out to examine the possibility of the existence of a hexacoordinate phosphorus intermediate (469) in the migration reaction (468) —> (470) of dimethyloxyphosphorylthreonine.606... 

Other theoretical studies discussed above include investigations of the potential energy profiles of 18 gas-phase identity S 2 reactions of methyl substrates using G2 quantum-chemical calculations," the transition structures, and secondary a-deuterium and solvent KIEs for the S 2 reaction between microsolvated fluoride ion and methyl halides,66 the S 2 reaction between ethylene oxide and guanine,37 the complexes formed between BF3 and MeOH, HOAc, dimethyl ether, diethyl ether, and ethylene oxide,38 the testing of a new nucleophilicity scale,98 the potential energy surfaces for the Sn2 reactions at carbon, silicon, and phosphorus,74 and a natural bond orbital-based CI/MP through-space/bond interaction analysis of the S 2 reaction between allyl bromide and ammonia.17... 

Such sterically hindered and unusual phosphorus compounds described here might serve as good model compounds for the theoretical studies as well as studies in organic or inorganic chemistry. 

RECENT SYNTHETIC, STRUCTURAL, SPECTROSCOPIC, AND THEORETICAL STUDIES ON MOLECULAR PHOSPHORUS OXIDES AND OXIDE SULFIDES... 

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