Structure and Physical Aspects

The structures of the carbanions generated by lithiated bases (or in the presence of lithium halides) from P-carbonylalkylphosphonates and phosphine oxides have been reviewed. 1  

A study of the conformation of 2-(diphenylphosphinoyl)-5,5-dimethyl-l,3-dioxane (28), both in solution and in the solid state, and comparisons with similar studies of various 1,3-dithiane analogues have been reported. 1 Certainly in the solid, and probably in solution, the diphenylphosphinoyl group preferentially occupies an equatorial position. 

The carbon bonding network around phosphorus centres can be determined in solids by the use of the double cross polarization l C n.m.r. technique as illustrated for the phosphine oxide (29).l Nine of the nineteen possible phosphine sulphides of the pentaphosphine (30) have been prepared (by progressive reaction of (30) with sulphur) and their structures have been investigated by 2D 3lp n.m.r. spectroscopy.20 

The conformational behaviour of 2-phosphoryl-l,3-dioxanes and dithianes continues to be an area of interest. Molecular mechanics methods have been applied to 2-phosphoryl-l,3-dioxane (34), the corresponding dithiane (35) and 2-thiophosphoryl-l, 3-dithiane (36).15 The relative stabilities of the axial and equatorial conformers in each case vary due to a combination of differing 1,3-axial interactions and anomeric effects. The conformer calculated to be the most stable for (34) and (35) is the structure given in each case. In the case of (36) the isomers are estimated to be of 

The absolute configuration of l-ter/-butylphenylphosphinyl-2-methylphenylphosphinylethane (38) has been determined by X-ray crystallography and, through chemical correlation, related to the corresponding ethene. O The oxide (39) has been synthesised and its structure investigated by n.m.r and X-ray methods.21 

Surprisingly the phosphine oxide (40) is very soluble in water22 oxide (40) also forms stable hydroxyphosphonium salts with acids and stable 1 1 adducts with amines. 

A range of diastereomeric 2-diphenylphosphinoyl-l,3-dioxanes have been synthesized either by Arbuzov reactions of tjopropyl 

A detailed study of I iSe and 3lp nuclear spin relaxation in tri(tertbutyI)phosphine selenide has been reported 6 and the kinetics and mechanism of formation of tetracoordinate P(V) sulphides from the reaction of tricoordinate phosphorus compounds with diaryl trisulphides have been investigated.1  

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The elements Zr and Hf are generally more similar in their chemistry than any other pair of congeneric elements as having nearly identical atomic or ionic radii, electronegativities, and elemental structures (actually, the similarities of Nb and Ta are nearly as close) however, their metal-rich chemistry is often surprising in its structural and physical aspects with fairly sharp distinctions emerging between the two elements [71]. 

Structural and Physical Aspects. - The stability of the various conformers of the phosphines oxides (269)- 211) has received theoretical consideration. A new triclinic polymorph of triphenylphosphine sulfide has been structurally characterised, together with a related triclinic polymorph of triphenylphos-phine. Two reports of the solid state crystal structure of the phenolic phosphine oxide (272) have appeared. A crystallographic study has confirmed that the product of electrochemical oxidation of o-diphenylphosphinoben-zenethiol is the disulfide-bridged bis(phosphine oxide) (273). Solid-state structural studies of the dioxides (274), the (i )-(-I-)-isomer of (275), 1-hexynyl(diphenyl)phosphine oxide,tribenzylphosphine oxide, and tris(t-butyl)phosphine selenide," have also been reported. 

Studying 3-D polymerization foresees an investigation of the total of all chemical and physical processes, useful properties of the pol3rmeric material and phenomena responsible for the formation of a polymer and, as a result, also for the formation of a complex. Therefore, knowledge of the structural and physical aspects of the microheterogeneous chemical mechanism of the 3-D radical polymerization is very important. 

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