Hans Bock

d-orbitaleffekte in silizium-substituierten π-elektronensystemen VI. Spektroskopische untersuchungen an alkyl- und silyläthylenen

Abstract 13 alkyl- and silylethylenes have been synthesized to determine their vertical ionization energies, characteristic IR frequencies, 1 H NMR signals, π → π* electronic transitions, halfwave reduction potentials and ESR spin densities of their radical anions. The result confirm d /π interactions in the ground state and d /π interactions in the excited state of silylethylene-π-electron systems. The inductive polarization + I (SiR 3 ) > + I (CR 3 ) could be evaluated from the substituent effect of the R 3 SiCH 2 group.

Estimation of hyperfine coupling constants of 29Si nuclei in the radical anions of trimethylsilyl-substituted π-electron systems

An attempt has been made to relate the coupling constant a Si of a 29Si nucleus in the radical anions of nine trimethylsilyl derivatives of π-electron systems to the spin populations ρ Si and of the silicon and the substituted carbon centre , respectively. For the parameter Q CSi of the relation an absolute value of circa 20 gauss is found, whereas Q Si appears not to be significantly different from zero. The coupling constants a Si calculated by means of this relation agree moderately well with the experimental values (standard error circa 0·6 gauss). An HMO model in which the trimethylsilyl substituents are treated as pseudo-π-centres, with the parameters h Si = -1·5 and k CSi = 0·55, reproduces satisfactorily the spin distribution in the corresponding radical anions.

d-Orbitaleffekte in silizium-substituierten π-elektronensystemen VII. Charge-transfer-übergänge in tetracyanoäthylenkomplexen von alkoxy- und siloxybenzolen und -biphenylen

Abstract The charge transfer maxima of the tetracyanoethylene complexes of 10 alkoxy- and siloxybenzenes and -biphenyls have been measured and are discussed by means of the calculated eigenvalue coefficients of the highest occupied molecular orbitals. The HMO model provides an excellent correlation with the experimental data and thus confirms the postulated (dSi←nO)π bond in siloxy-substituted aromatic compounds.

Metall [O] -Verbindungen mit nichtaromatischen Stickstoffs-Systemen V

Die Komplexbildungsfähigkeit von Triphenylphosphin-imin (C6H5)3P = NH, -oxid (C6H5)3P = O und -äthylen (C6H5)3P = CHCH3 wird verglichen: Die verschiedenen Ph3P=X-Systeme setzen sich mit Molybdän- und Wolfram-hexacarbonyl, Cycloheptatrien-Molybdäntricarbonyl oder Bis (dialkylcyanamid) -Molybdäntetracarbonyl je nach Reaktionsbedingungen zu den Komplexen [ (Ph3P =X)2Me (CO) 4] (Me = Mo, W und X = NH, O), [ (Ph3P =X) 3Mo (CO) 3] (X = O, CHCH3) sowie dem ungewöhnlich stabilen, zweikernigen [ (Ph3P = NH) 2Mo (CO) 3] 2 um. Die Strukturen und der P=X/Metall-Bindungstyp werden an Hand der Schwingungsspektren diskutiert.

Two-electron reduction of 1,1,4,4-tetraphenylbutadiene by sodium or potassium to but-2-ene-1,4-diyl salts of different structure

The reduction of 1,1,4,4-tetraphenylbutadiene in ether solution at sodium or potassium metal mirrors proceeds via CC double bond shifts and yields either a monomeric contact ion triple unit {tetraphenylbutadiene2–-[Na+(dimethoxyethane)2]2}1, or a polymeric contact ion aggregate, [tetraphenylbutadiene2–(K+ diethyl ether)2]∞.

Notizen: Photoelectron Spectra and Molecular Properties, XLVI.

Photoelectron spectra of nitroso compounds X-NO (X = CH3, OCH3) are assigned using chemical relationship and CNDO calculations. Comparison of ionization energies and of calculated charge distributions includes as well derivatives X = N(CH3)2, Cl, F.

Photoelektronen-Spektren und Moleküleigenschaften, LXIII Ionisierungsenergien von Phenyl-Methyl-Tellurid und Vergleich der Effekte von Sauerstoff-, Schwefel-, Selen- und Tellur-Substituenten auf das Benzol-π-System / Photoelectron Spectra and Molecular Properties, LXIII Ionization Energies of Phenyl Methyl Telluride and Comparison of Effects of Oxygen, Sulphur, Selenium and Tellurium Substituents on the Benzene π System

The photoelectron spectrum of H5C6-Te-CH3 displays in its low energy region overlapping bands of gas-phase conformers. Depending on the dihedral angle between the plane of the phenyl ring and the tellurium lone pair, the π conjugation amounts to only 0.1 eV and 0.3 eV, respectively. These values are compared to the considerably larger ones found for the analogous phenyl derivatives H5C6-X-CH3 with X = O, S and Se.