Theoretical studies butadiene complexes

Another type of interaction is the association of radical ions with the parent compounds. Recently (118), a theoretical study was reported on the interaction of butadiene ions with butadiene. Assuming a sandwich structure for the complex, the potential curve based on an extended Hiickel calculation for two approaching butadienes (B + B) revealed only repulsion, as expected, while the curves for B + and B + B" interactions exhibit shallow minima (.068 and. 048 eV) at an interplanar distance of about 3.4 A. From CNDO/2 calculations, adopting the parameter set of Wiberg (161), the dimer cation radical, BJ, appears to be. 132 eV more stable than the separate B and B species, whereas the separate B and B species are favored by. 116eV over the dimer anion radical, BJ. This finding is consistent with experimental results formation of the dimer cation radical was proved in a convincing manner (162) while the attempts to detect the dimer anion radical have been unsuccessful. With other hydrocarbons, the reported formation of benzene dimer anion radical (163) represents an exceptional case, while the dimeric cation radical was observed... 

A theoretical study of the Diels-Alder reactions between 1,3-butadiene and, respectively, cyclopentadiene and 2H-phosphole, has revealed a remarkable similarity between the two reactions. Further studies of photocycloaddition reactions of phosphole moieties have also been reported. Transition metal complexes of phospholide anions continue to attract attention, and in particular the chemistry of phosphaferrocene systems remains a major interest . The past year has also seen significant activity in the chemistry of di- and tri-phospholes, related polyphospholide anions, and also heterodiphosphole systems. Routes have been developed to the diphosphonio-l,2-diphospholes 356,... 

Hofmann used a triptycene type backbone for preparing diphosphite 145, in overall 40% yield from three steps, starting from a conveniently substituted anthracene. Reaction of the substituted anthracene with dimethyl fumarate under microwave irradiation considerably reduced reaction time to prepare the triptycene derivative. After deprotection, the corresponding diol was then treated with chlorophosphite to give 145. The ligand was used in theoretical studies on rhodium(i)-catalysed hydroformylation of butadiene. The same authors also prepared iridium complex 146, from the already known diphosphite, which was used for the same purpose. 

The potential use of photoacoustic Fourier transform IR spectroscopy in the quantitative analysis of polymers was explored by studying the determination of vinyl acetate in EVA, acrylonitrile in nitrile rubber, ethylene in EPDM, and styrene and vinyl butadiene in SBR. Despite the theoretical complexities of this technique, simple quantitative relationships could be found for many of these polymer analyses. 24 refs. 

Structural characterization of (butadiene)tricarbonyliron complexes has been carried out by microwave spectro-scopy/" " solution calorimetry/" pulsed-electron high pressure mass spectrometry/ infrared spectro-scopy/ and vibrational overtone spectroscopy/ Theoretical investigations using DFT have also been reported/ " Extended Hiickel calculations have been employed to study structure and stereodynamic relationships in a variety of ( 7" -diene)iron carbonyl complexes/ ... 

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