Phosphorus–nitrogen compounds. Part VI. Aminolysis of octachlorocyclotetraphosphazatetraene and the crystal structure of 2- trans-6-bis(n-propylamino)-2,4,4,6,8,8-hexakis- tert-butylaminocyclo-2λ 5, 4λ 5, 6λ 5, 8λ 5-tetraphosphazatetraene

Abstract

The reactions of 2- trans-6-N 4P 4(NHPr n ) 2Cl 6 ( 2), which was obtained from N 4P 4Cl 8 ( 1) and n-propylamine, with pyrrolidine and t-butylamine in different solvents have been studied. Compound ( 2) gave two different products, namely monocyclic ( 3 and 5) and bicyclic ( 4 and 6) phosphazenes. Compounds ( 2– 6) have been characterized by elemental analysis, IR, 1H-, 13C-, 31P NMR, HETCOR and MS and the structure of compound ( 5) has been examined crystallographically. The bicyclic phosphazene ( 6) is the first exciting example of bicyclic phosphazenes containing chlorine atoms, in the literature. The formation mechanisms of bicyclic phosphazenes are re-considered by taking into account the synthesis of compound ( 6), which contains three stereogenic phosphorus atoms. Compound ( 5) crystallizes in the monocyclic space group P2 1/ n with a=13.974(2), b=17.836(5), and c=18.683(4) Å, β=98.50(1)°, V=4605.4(2) Å 3, Z=4 and D x =1.051 g cm −3. It consists of a non-centrosymmetric, non-planar phosphazene ring in a saddle conformation, with two n-propylamino (in 2- trans-6 positions) and six bulky t-butylamino side groups. The bulky substituents are instrumental in determining the molecular geometry.