Phosphorus–nitrogen compounds. Part XXVI. The influence of benzene on the 1H n.m.r. spectra of some mononuclear phosphorus(V) amides and dimethylaminocyclotriphosphazatrienes

Abstract

The ¹H n.m.r. spectra of a range of mononuclear phosphorus(V) compounds, P(X)R_3–n(NMe₂)_n(X = O or S, n= 1–3, and R = amino, alkylamino, chloro, phenoxy, or phenyl), have been measured in carbon tetrachloride and benzene solution. The proton signal is always shifted upfield in benzene solution relative to that measured in carbon tetrachloride solution. These results are best rationalised in terms of a weak complex formation between the phosphorus compound and benzene. Similar solvent shifts were observed in the ¹H n.m.r. spectra of dimethylamino-derivatives of hexachloro- and hexabromo-cyclotriphosphazatriene, N₃P₃Cl_6–n(NMe₂)_n(n= 1–4 and 6) and N₃P₃Br_6–n(NMe₂)_n(n= 1–3), respectively. For a given degree of chlorine (or bromine) replacement, dimethylamino-groups cis to one another were shifted upfield to a greater extent than those trans to one another.