Harald Siegl

Synthesis and Structure of P7[Si(SiMe3)3]3 (Tri(hypersilyl)heptaphosphanortricyclane)

Summary. By reaction of sodium-potassium phosphide (prepared from white or red phosphorus and sodium-potassium alloy) and chlorotris(trimethylsilyl)silane, P7[Si(SiMe3)3]3 has been prepared in high yields. An X-ray analysis proved that the molecule is composed of a P7-nortricyclane cage substituted with three Si(SiMe3)3 groups and that two enantiomers are present in crystals grown from benzene. The 31P NMR spectrum shows the complex splitting pattern of an A[MX]3 spin system. 31P chemical shifts and 31P, 31P one-bond and two-bond coupling constants have been calculated by numerical simulation of the spectrum.Zusammenfassung. Durch die Reaktion von Natrium-Kalium-Phosphid (darstellt aus rotem oder weißem Phosphor und Natrium-Kalium-Legierung) mit Chlortris(trimethylsilyl)silan konnte P7[Si(SiMe3)3]3 in hoher Ausbeute dargestellt werden. Die Charakterisierung des mit drei Si(SiMe3)3-Gruppen substituierten P7-Nortricylan-Käfigs erfolgte mit Hilfe der Röntgenstrukturanalyse. In aus Benzol gezüchteten Kristallen sind beide Enantiomere enthalten. Das 31P-NMR-Spektrum zeigt das komplexe Aufspaltungsmuster eines A[MX]3-Spinsystems. Die 31P Verschiebungen und die 31P, 31P Kopplungskonstanten über eine oder zwei Bindungen wurden durch numerische Simulation des Spektrums berechnet.

Synthesis, spectroscopy and structure of phenylated cyclopentasilanes

Abstract Phenylated cyclopentasilanes Si5Ph10−nXn with X = OSO2CF3, F, Cl, Br, I or H and n = 1 or 2 were prepared in high yield by dearylation of Si5Ph10 with trifluoremethanesulphonic acid (CF3SO3H) and subsequent reaction with lithium or potassium halides and LiAlH4. The trans-1,3-isomers of Si5Ph8X2 were isolated by crystallization and the crystal structure of trans-1,3-difluorooctaphenyl-cyclopentasilane was determined. cis-1,3-, trans-1,2- and cis-1,2-Si5Ph8X2 were identified and characterized by 1H, 19F and 29Si NMR spectroscopy. SiSi coupling constants were measured using INADEQUATE pulse sequences.

Tridecamethyl-1-phospha- and tridecamethyl-1-arsa-2,3,4,5,6,7,8-heptasilabicyclo[2.2.2]octane

Abstract The octaheterobicyclo[2.2.2]octanes MeSi(SiMe2SiMe2)3E(E = P, As) have been prepared in high yields (up to 50%) from the alkali metal phosphide or arsenide Na 3 E K 3 E and the heptasilane MeSi(SiMe2SiMe2Cl)3 The cages were isolated by crystallization from heptane and the crystal structure of the arsenic compound was determined. The synthesis of the heptasilane MeSi(SiMe2SiMe2Cl)3 is described too. All compounds were characterized by multinuclear NMR spectroscopy (1H, 29Si, 13C, 31P) as well as elemental analysis.

Molecular structure of ButCl2SiSiCl2But in the gas phase by electron diffraction and ab initio calculations. Molecular structures of the compounds ButX2SiSiX2But (X = Cl, Br or I) by vibrational spectroscopy, X-ray crystallography and ab initio calculations

The series of compounds ButX2SiSiX2But (X = Cl, Br and I) have been studied by X-ray crystallography, vibrational spectroscopy and ab initio calculations. The solids were all found to be anti and the vibrational spectra are consistent with this observation. The molecular structure of 1,2-di-tert-butyltetrachlorodisilane, ButCl2SiSiCl2But, has also been determined in the gas phase by electron diffraction (GED) and ab initio molecular-orbital calculations. The conformation is distorted slightly from the fully staggered arrangement, with ϕ(CSiSiC) 167.7(11)°. Important structural parameters (ra) include: Si–Si 238.0(7) pm, Si–C 187.2(7) pm, C–C 154.3(2) pm, C–H 114.2(4) pm, Si–Si–C 119.8(6)°, Cl–Si–Cl 105.5(8)° and C–Si–Si–C 167.7(11)°. These experimental observations are supported by theoretical predictions obtained at the MP2/6-31G* level.