Synthesis and nuclear magnetic resonance spectroscopy of geometrical isomers of 1,3,5-Trimethyl-2,4,6-tris(p-methylphenoxy)-2,4,6-trioxocyclotri-phosphazane: X-Ray crystal structure of the trans isomer

Both cis and trans isomers of tri(N-methyl)tris(p-methylphenoxy)trioxocyclotriphosphazane,$N_3Me_3P_3O_3(OC_6H_4Me-p)_3$, have been prepared by the thermal rearrangement of the respective trimethoxycyclophosphazenes, $N_3P_3(OC_6H_4Me-p)_3(0Me)_3$. The crystal and molecular structure of the trans isomer has been determined; it crystallises in the P1 space group with a = 8.444(1), b = 11.753(1),c = 14.196(1)\AA,\alpha = 97.408(8), \beta = 92.487(10),\gamma = $102.325(10)^0$,andZ = 2.The structure has been solved by direct methods and refined to a R value of 0.060. The six-membered $N_3P_3$ phosphazane ring adopts a twist-boat confirmation. The structural data have been used to explain the n.m.r. spectroscopic features. A chair conformation is proposed for cis- $N_3Me_3P_3O_3-(OC_6H_4Me-p)_3$ on the basis of n.m.r. data