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Abizanda D, Crespo O, Gimeno MC, Jimenez J, Laguna A: Synthesis and structure of new carborane-substituted cyclotriphosphazenes. Chemistry. 2003 Jul 21;9(14):3310-9.
The reactions of [N (3) P (3) Cl (6)] with one, two, or three equivalents of the difunctional 1,2-closo-carborane C (2) B (10) H (10)[CH (2) OH](2) and K (2) CO (3) in acetone have been investigated. These reactions led to the new spiro-closo-carboranylphosphazenes gem-[N (3) P (3) Cl (6-2n)[(OCH (2))(2) C (2) B (10) H (10)](n)] (n=1 (1), 2 (2)) and the first fully carborane-substituted phosphazene gem-[N (3) P (3)[(OCH (2))(2) C (2) B (10) H (10)](3)] (3). A bridged product, non-gem-[N (3) P (3) Cl (4)[(OCH (2))(2) C (2) B (10) H (10)]] (4), was also detected. The reaction of the well-known spiro derivatives [N (3) P (3) Cl (2)(O (2) C (12) H (8))(2)] and [N (3) P (3) Cl (4)(O (2) C (12) H (8))] with the same carborane-diol and K (2) CO (3) in acetone gave the new compounds gem-[N (3) P (3)(O (2) C (12) H (8))(3-n)[(OCH (2))(2) C (2) B (10) H (10)](n)] (n=1 (5) or 2 (6), respectively), without signs of intra- or intermolecularly bridged species. Upon treatment with NEt (3) in acetone, compound 5 was converted into the corresponding nido-carboranylphosphazene. However, the reaction of gem-[N (3) P (3)(O (2) C (12) H (8))(2)[(OCH (2))(2) C (2) B (10) H (10)]] (5) with NEt (3) in ethanol instead of acetone proceeded in a different manner to give the new compound (NHEt (3))(2)[N (3) P (3)(O (2) C (12) H (8))(2)(O)[OCH (2) C (2) B (9) H (10) CH (2) OCH (2) C H (3)]] (7). For compounds with two 2,2'-dioxybiphenyl units, gem-[N (3) P (3)(O (2) C (12) H (8))(2)[(OCH (2))(2) C (2) B (10) H (10)]] (5), (NHEt (3))[N (3) P (3)(O (2) C (12) H (8))(2)[(OCH (2))(2) C (2) B (9) H (10)]] (8), and (NHEt (3))(2)[N (3) P (3)(O (2) C (12) H (8))(2)(O)[OCH (2) C (2) B (9) H (10) CH (2) OCH (2) C H (3)]] (7), a mixture of different stereoisomers may be expected. However, for 5 and 7 only the meso compounds seem to be formed, with the same (R,S)-configuration as in the precursor [N (3) P (3) Cl (2)(O (2) C (12) H (8))(2)]. The reaction of 5 to give 8 seems to proceed with a change of configuration at one phosphorus center, giving a racemic mixture. The crystal structures of the nido-carboranylphosphazenes 7 and 8 have been confirmed by X-ray diffraction methods. |
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