Studies Based on Molecular Orbital Theory

The steric and electronic structures of tervalent aminoiminophosphines (4) have been studied by X-ray crystallography and quantum chemical calculations of aminoiminophosphines and some related model compounds. It was found that n- s interaction plays a significant role in stabilising the sterically-hindered cis-form. The structural consequences of n(N)-+p (NSP) conjugation in these compounds do not correspond to the classical case and only a qualitative explanation can be given. 

Rotational barriers of the P-C bond in phosphoryl- and thiophosphoryl-stabilised carbanions have been studied by ab initio calculations on the 2-oxo-(and thioxo)-2-methyl-l,3,2-diazaphosphirane-(7) and -diazaphospholidine anions (8), at MP4(SDQ)/6 - 31+G //HF/6 - 31+G +ZPE levels. MNDO calculations have shown that 2-pyrrolinones cannot be phosphorylated with phosphorus nucleophiles.  

Ab initio calculations carried out on three 1,3,2-diazaphosphole derivatives, eg., 1, at the MP2/6-31 lG(d,p) level, gave rise to structural and energy data that are interpreted in context of its aromaticity. The 1,3,2-diazaphospholenium ion 2 also has a substantial degree of aromatic stabilisation energy (24.0 kcal mol ) in fact it is comparable to that of pyrrole. Cyclic delocalisation is supported by an analysis of computed charge distribution data, natural bond orbital data, bond 

Organophosphorus Chemistry, Volume 29 The Royal Society of Chemistry, 1999 

The molecular and electronic structure of P- and C-halogen-substituted phosphaalkenes have been studied using quantum-chemical calculations together with X-ray diffraction data. The introduction of an electronegative 

The structures of fluorophosphine, PH2F, and chlorophosphine, PH2CI, have been determined by ab initio calculations, and the pyramidal geometry of the X Ai ground state of the Pp3 cation has been confirmed. An ab initio study of the internal rotation levels of the terminal methyl group in the ethylphosphine molecule CH3CH2PH2 has been undertaken. Ab initio calculations on ethyldi-fluoro-, ethyldichloro-, and ethyldimethyl-phosphines, CH3CH2PX2 have been compared with conformational stabilities obtained from temperature-dependent FT-IR spectra recorded in liquefied xenon solutions. Theoretical gas-phase proton affinities of arylphosphines have also been reported at the MP2 level. 

The electron distribution in PCI5 has been studied by ab initio calculations, and the radical cation of trimethylphosphine oxide, Me3P -0, has also been examined.  

---