Synthesis, structural, and stereogenic characterizations of new trispirocyclotriphosphazenes

Abstract

In this study, trispirophosphazenes containing biphenyl-2,2 0 -dioxy and ferrocenyldiamino groups were synthesized to investigate their stereogenic and structural properties. For this purpose, monospiro (1) and trans/cis-dispiro (2 and 3) cyclotriphosphazenes were obtained from the reactions of hexachlorocyclotriphosphazatriene (N 3 P 3 Cl 6 ; trimer; HCCP) with N-ethyl-N 0 -ferrocenylmethyl-ethylenediamine. Subsequently, bis(biphenyl-2,2 0 -dioxy)-substituted ferrocenylphosphazene (4) was prepared from the reaction of an equimolar amount of monoferroceylphosphazene (1) with two equimolar amounts of dipotassium biphenyl-2,2 0 -dioxide. Reactions of equimolar amounts of 2 and 3 with equimolar amounts of dipotassium biphenyl-2,2 0 -dioxide yielded trans-( 5) and cis-( 6) trispirophosphazenes, respectively. Characterizations of all trispiro compounds were made using 1 H, 13 C, and 31 P NMR spectra. In addition, trispirophosphazenes 5 and 6 have two equivalent stereogenic P-centers. Trans-5 and cis-6 are expected to exist in racemate and meso forms. The molecular and crystal structures of the two phosphazenes (4 and 5) were clarified by single-crystal X-ray crystallography. Also, since the absolute configuration of one enantiomer of 5 is found to be RR, the other must be SS.