Conformational polymorphism in a chiral spiro-cis-ansa-bridged cyclotriphosphazene derivative

Abstract

P 3. Recrystallization of this fraction from different solvents results in the formation of two different crystalline forms. The rod morphology formed in dichloromethane±n-hexane (1:1) produces a triclinic structure with three molecules in the asymmetric unit. These three molecules adopt different conformations as a result of two NH groups¯ipping in an ansa-bridged ring system. The plate morphology crystals, grown in dichloromethane±n-hexane±ethyl acetate (1:1:1), produce a C-centred monoclinic structure that adopts a conformation that is essentially the same as one of the forms in the triclinic structure.

Chiral configurations in cyclophosphazene chemistry

“…There are a few crystallographic examples for Type II(9) rac1 or rac2 (66c [76], 69 [103], 70a,b and 71 [60]). There is a special case "pseudoasymmetric center" for Type II(2) and Type II (6) which are comprised of four steroisomers: two different meso of cis and two enantiomeric forms of trans and it is mentioned for the first time for phosphazene compounds in this review.…”

Enantiotropic conformational polymorphism in 2,2,4,4-bis-(2′,2′-dimethylpropane-1′,3′-dioxy)-6,6-dichlorocyclotriphosphazene

“…6 Three different crystalline modifications of the pentameric fluoride, N 5 P 5 F 10 , have been reported, two of which have been structurally characterized. 7 Polymorphism involving derivatives of the trimer form of cyclophosphazenes (N 3 P 3 Cl 6 ) have been reported for a chiral spiro-cis-ansa-bridged cyclophosphazene derivative, 8 for the hexa-substituted derivative, 2,2,4,4,6,6-hexaisothiocyanatocyclophosphazene 9 and for syn/anti conformational forms of a spermine-bridged cyclophosphazene. 10 The cyclophosphazene ring in the tetrameric, N 4 P 4 Cl 8 , and pentameric, N 5 P 5 F 10 , forms are non-planar and polymorphism results from different conformations of the phosphazene rings, whereas the six-membered ring of trimeric cyclophosphazene, is essentially planar and polymorphism results from different orientations of the bonded side groups.…”