2,6-Diazidohexaphenylcyclophosphonitrile tetramer

Article abstract of DOI:10.1021/ic50046a014

Reaction of 2,6-dichlorohexaphenylcyclophosphonitrile tetramer with lithium azide in refluxing acetonitrile gave cis- and trans-2,6-diazidohexaphenylcyclophosphonitrile tetramer (cis-II and trans-II). Structures were assigned the two isomers of II on the basis of observed dipole moments: for cis-II, mp 147.5-148.0°, dipole moment 3.7 D.; for trans-II, mp 206-208°, dipole moment 0.2 D. In refluxing acetonitrile an azide ion catalyzed equilibrium exists with K_eq = 2.6 for the reaction cis-II = trans-II, ΔG₃₅₅ = 0.67 kcal/mole. In a kinetic study carried out with a thermal balance, it was found that cis-II and trans-II both decompose above 200° by first-order kinetics with activation energies of 34.2 and 37.5 kcal/mole, respectively. In chemical reactions with triphenylphosphine and heptafluoropropyldiphenylphosphine, trans-II underwent the expected reactions at each azide group to eliminate 2 moles of nitrogen and to add 2 moles of phosphine linked by N=P bonds to give trans-2,6-bis(triphenylphosphazido)hexaphenylcyclophosphonitrile tetramer and trans-2,6-bis(heptafluoropropyldiphenylphosphazido)hexaphenylcyclophosphonitrile tetramer. Similarly, cis-II and triphenylphosphine gave cis-2,6-bis(triphenylphosphazido)hexaphenylcyclophosphonitrile tetramer. Reaction of cis-II with 1,4-bis(diphenylphosphino)-butane did not lead to the expected 1:1 polymer but gave instead the cyclic 1:1 addition product cis-2,6-[P,P-butanobis-(diphenylphosphazido)]hexaphenylcyclophosphonitrile tetramer.