, 41  Synthese, Struktur und Eigenschaften neuer silyl-, germyl-und stannylsubstituierter Heptaphosphane(3) P7(MPh3)3 mit M = Si, Ge, Sn Chemistry and Structural Chemistry of Phosphides and Polyphosphides, 41  Synthesis, Structure and Properties of New Silyl, Germyl and Stannyl Substituted Heptaphosphanes(3) P7(MPh3)3 with M = Si, Ge, Sn Silyl-, Germyl-and Stannyl-substituted H eptaphosphanes(3), 3,5,7-T riphenylm etalla[2.2.1.02'6]hepta-phosphanes, Structures, Raman Spectra, 31P NM R Spectra New derivatives P7(M Ph3) 3 (M = Si, G e, Sn) o f the heptaphosphanortricyclen cage were synthesized by reactions o f P7(SiM e,) 3 with com pounds CIMPh,. The driving force o f the reaction is the lower solubility o f the P7(M P h,) 3 com pounds. W hereas crystals of P7(SiM e3) 3 are enan-tiom orphs, the new com pounds P7(M Ph3) 3 crystallize as racemates. With decreasing M size, the nortricyclen cage P7 is slightly twisted about the 3-fold axis. The main P -P bond lengths in the cage follow the relation A (basal) — 221.8 pm > B (basal-equatorial) = 219.0 pm > C (equato-rial-apical) = 218.5 pm. The m ean bond lengths P —Si = 228.6 and P —Ge = 234.9 and P —Sn = 253.5 pm are slightly larger than the standard single bond distances. The IR absorptions show only very small M -dependent variations in the characteristic internal cage vibrations. Similar effects are recognized in the 3,P NM R chem ical shifts.