Chain and Ring Phosphorus Compounds—Analogies between Phosphorus and Carbon Chemistry

Verbindungen mit einem Gerust aus Phosphor-Ketten oder -Ringen waren bis vor etwa 15 Jahren „Exoten” auf dem Gebiet der Nichtmetallchemie. Neben Molekulen mit zwei aneinander gebundenen P-Atomen und sporadisch entdeckten monocyclischen Phosphorskeletten kannte man lediglich Feststoffe undefinierter Zusammensetzung und Struktur. Seither hat sich der Kenntnisstand erstaunlich gewandelt: Zwischen PH3 und senen Derivaten einerseits und den hochmolekularen Modifikationen des elementaren Phosphors andererseits wurde eine unerwartete Vielfalt wohldefinierter und -strukturierter Verbindungen gefunden, die vielfache Bezuge zur Kohlenstoffchemie aufweisen. Das aber auch bei „kleinen” phosphorhaltigen Molekulen noch Uberraschungen moglich sind, bestatigt das ebenfalls neu erschlossene Teilgebiet der Phosphor-Dreiringverbindungen.

Ketten‐ und ringförmige Phosphorverbindungen – Analogien zwischen Phosphor‐ und Kohlenstoffchemie

Formation, structure (stereochimie et stereodynamique), et donnees de spectroscopie RMN des composes du titre

Molecular and electronic structure of penta- and hexacoordinate silicon compounds

CH stretching frequencies, bond lengths and dissociation energies

Spin-spin coupling tensors for one-bond coupling between main group elements are calculated using a sum-over-states of relativistically parameterized extended Huckel (REX) wavefunctions and the relativistic analogue of Ramsey's theory. All parameters, including the tabulated magnetic hyperfine integrals, come from relativistic (or non-relativistic) atomic Hartree-Fock calculations, affording a systematic comparison of these two cases. The results reconfirm the strong relativistic increase of K(XH) in XH4, X = C-Pb, and the role of the new, isotropic term K ps . The relativistic increase of the relative anisotropy R = (K ‖-K ⊥)/K is found to be a rather general phenomenon. Its origin is traced to the s-tp 1/2 contribution and, ultimately, to a phase factor for p 1/2 orbitals. Thus, for example, the R(PbC) in Pb(CH3)4 is predicted to be larger than the corresponding R(SnC) in Sn(CH3)4. For molecules having lone pairs, both the increase of Z along a column and the relativistic effects diminish the 1 K, makin...

Relativistically parameterized extended Hückel calculations

Electron diffraction studies of the hydrides Si2H6 and P2H4

An electron diffraction determination of the molecular structure of methyl silyl ether

The molecular structure of phenyl silyl ether C6H5OSiH3 has been studied by the sector-microphotometer method of electron diffraction. The Si—O bond length is 1.648 ± 0.007 A, the C—O bond length is 1.357 ± 0.009 A, the Si—O—C angle is 121 ± 1° and the dihedral angle between the Si—O—C plane and the aromatic ring is 68 ± 3°. These results are discussed and compared with those for similar molecules.

J. M. Freeman

Papers

Electron diffraction studies of the hydrides Si2H6 and P2H4

An electron diffraction determination of the molecular structure of methyl silyl ether

Electron diffraction study of phenyl silyl ether

An electron diffraction determination of the molecular structures of trichloro- and trifluoro-silyl-dimethylamine

Bestimmung der molekularstruktur von dimethylaminodifluorphosphin und aminodifluorphosphin in der gasphase durch elektronenbeugung