H. G. v. Schnering

Substituted heptaphosphanortricyclenes: Derivatives and homologues of P7(SiMe3)3

Abstract Homologues and derivatives of P7(SiMe3)3 can be synthesized from Li3P7·3solv or Na3P7, or by cleavage of the PSiMe3 bond with RX. The reaction of Li3P7·3DME with the halogen-containing compounds Ph3SiCl (Ph  C6H5), H3SiI, Me3SnBr (Me  CH3), i-C3H7Br, CpFe(CO)2Br yields P7(SiPh3)3, P7(SiPh3)3, P7(SnMe3)3, P7(i-C3H7)3 and P7[Fe(CO)2Cp]3. Na3P7 reacts with Me3MCl (M  Si, Ge, Sn) yielding P7(MMe3)3. The reaction of Li3P7·3DME with PMe2Cl leads to P2Me4, but P7(PMe2)3 is not formed. Cleavage of the PSi bond in P7(SiMe3)3 by Me3SnBr or Me3SnCl gives the compounds P7(SiMe3)3-n(SnMe3)n with (n = 1, 2 or 3) depending on the molar ratio. The reaction with HI yields mixtures of H3-nP7(SiMe3)n,while I2 converts P7(SiMe3)3 into P2I4, PI3 and Me3SiI. Crystals of the Ge and Sn compounds are less sensitive towards oxidation and hydrolysis than P7(SiMe3)3. The compounds have been identified by 31P NMR and mass spectra. An X-ray structure analysis has shown P7(MMe3)3 (M = Si, Ge, Sn, Pb) to be isotypical (space group P21 (No. 4). The compounds crystallize as pure enantiomers. Bond lenghts and angles vary with their position in the P7 cage (PP = 222.2,218.8, and 218.0 pm) and are almost unaffected by the substitution. The PM bond lengths are 228.8 (Si); 235.5 (Ge); 253.9 (Sn); 261.7 pm (Pb), showing a small lengthening with respect to calculated values. The cone angle of the bridging P atom decreases with increasing size of M. The P7 cage vibrations are almost unchanged by the subsitution, whereas ν(PM) and ν(MC3) change in the usual manner.