| Research Abstract |
Various polymers of sterically protected 3,4-diphosphinidenecyclobutenes, which are unique bidentate ligands having phosphorus-carbon double bonds, were prepared and their properties were studied. For example, a new sterically protected 3,4-diphosphinidenecyclobutene, containing 4-(4-vinylphenyl)butyl group at the 1- and 2-positions, was prepared and converted to a polymer. In the successive reaction of bis[(2,4,6-tri-t-butylphenyl)phosphino]diynes with t-butyllithium and 1,2-dibromoethane, 3,4-diphosphinidenecyclobutene derivatives having ring-fused structures were obtained as major products along with diphosphinidenecyclobutene polymers. Sterically protected 3,4-diphosphinidene-1,2-dithienylcyclobutenes were also prepared and converted to polymers and/or oligomers, via functionalization of the thienyl moieties. Some polymers and oligomers, as well as their monomers, were allowed to react with bis(acetonitrile)dichloropalladium or bis(acetonitrile)dichloroplatinum to give metal comple
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xes of the bidentate ligands. Structures of some diphosphinidenecyclobutene monomers and their transition metal complexes were analyzed by X-ray crystallography. A relatively large geometrical change induced by the complex formation was exhibited in the case of 3,4-diphosphinidenecyclobutenes having ring-fused structures.
Moreover, some new sterically protecting groups were developed. A sterically protecting auxiliary of the metacyclophane type was newly developed and applied to preparations of unsymmetrically substituted diphosphene and 1,3-diphosphaallene. Unsymmetrical 1,4-diphosphabutatriene was prepared for the first time, using the sterically protecting group of metacyclophane type, and the properties were studied. Sterically hindered aryl substituents having an electron-donating group at the o- or p-positions, were also developed. Thus, 2,4-di-t-butyl-6-(phenoxymethyl)phenyl group and 2,6-di-t-butyl-4-methoxyphenyl group were developed and the substituents were applied to preparations of diphosphenes as well as dichlorophosphines and fluorenylidenepbosphines. Structures of some low coordinated phosphorus compounds bearing the electron-donating sterically demanding groups were studied by X-ray crystallography and the effect of the substituents were discussed. Less
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