Synthesis and Structure of Carborane-Substituted Cyclic and Polymeric Phosphazenes

Article abstract of DOI:10.1021/ja00392a019

The synthesis of the first carborane-substituted cyclophosphazenes together with the preparation, by two different approaches, of the first carborane-substituted phosphazene linear polymers is reported.The cyclic derivatives IV are both precursors and model compounds for the analogous polymeric derivatives VI.The crystal and molecular structure of IV (R = phenyl) has been investigated by single-crystal X-ray diffraction techniques.The molecule contains a planar phosphazene trimer ring bound directly to the phenyl carboranyl group through a P-C bond.The absence of steric and electronic influences by the phosphazene and carboranyl units on each other is discussed.The crystal of IV (R = phenyl) are monoclinic with the space group P2₁/n and with a = 9.476 (3) Angstroem, b = 12.984 (2) Angstroem, c = 18.726 (3) Angstroem and β = 100.11 (3) deg with V = 2268.2 (3) Angstroem³ and Z = 4.The P-N bond distances are all similar and average 1.574 Angstroem.The P-C bond length is 1.820 Angstroem, and the Cl-P-C angle was found to be 102.4 deg.The reaction between high molecular weight poly(dichlorophosphazene), (NPCl2)ⁿ, and methyl- or phenyl-1-lithio-o-carborane was also studied.Chlorine substitution is a slow process, and is accompanied by chain cleavage.The nucleophilic replacement of the halogen atoms yielded high polymers of structure IX that contain up to 15percent of the side groups as carboranyl units.The remaining chlorine atoms were replaced by treatment with sodium trifluoroethoxide.The properties and structure of the macromolecules are discussed.