Tetracovalent species

Phosphoranyl radicals (1) are tetracovalent species most typically formed by the oxidative addition reaction shown in... 

The role of orbital orientation in organic and enzymatic reactions has been of considerable current interest. Deslongchamps and coworkers(1) in studying tetracovalent carbon species have recently demonstrated selective cleavage of bonds which are trans, antiperiplanar (app) to lone pairs on directly bonded oxygen and nitrogen atoms. 

Molecular orbital calculations have also provided theoretical justification for these stereoelectronic effects in tetracovalent and pentacovalent phosphorus species (2-7). As has been shown in molecular orbital calculations on the X -P-X2 (X = 0,N) structural fragments, the X.-P bond is strengthened (as indicated by an increase in the Mulliken overlap population) while the P-X3 bond is weakened when the X atom lone pair is app to the P-X3 bond. Thus, in the g,t conformation of dimethyl phosphate (Structure ll the overlap population for the trans P-0 bond is. 017 electron lower than the overlap population for the gauche P-0 bond. As shown for g,t dimethyl phosphate one lone pair (shaded in 1) on the gauche bond oxygen is app to the trans bond, while no lone pairs on the trans bond oxygen are app to the gauche bond. Thus, the weakest X.-P bond has one app lone pair and no lone pairs on X. app to the P=X2 bond. 1... 

Methyl triflate is a powerful alkylating agent, which methylates tetracovalent P=0, P=S, and P=Se systems at the oxygen, sulfur, and selenium atoms, respectively (1,2, 3). Its reaction with analogs containing a hydrogen substituent (e .j>., phosphinate, phosphonate or secondary phosphine oxide species), however, appears not to have been reported. 

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