3 results for Asamizu, Toshie

  • Stabilisation effects of ferrocenylalkyl groups on hydrides of heavier main group elements

    Asamizu, Toshie (2013)

    Doctoral thesis
    University of Waikato

    New hydrides of heavier p-block main group elements with a ferrocenylalkyl moiety, Fc(CH₂)nEHm (Fc = (CpFeC₅H₄-); E = P, As, Si, Ge or Se; n = 1, 2, 4, 6 or 11; m = 1, 2 or 3) and FcCH₂P(R)H (R = CH₃, C₆H₁₁ or p-CH₂C₆H₄NO₂), have been synthesised and characterised. Although some precursors of the desired hydrides, i.e. Fc(Cl)C=C(SnCl₃)H and (FcCH₂Te)₂, which are also new compounds, could be prepared, the syntheses of the corresponding desired hydrides, FcCH₂EHn, were unsuccessful probably due to their extreme instabilities. Some related primary phosphanes, [CpFeC₅H₃(CH₂OH)(CH₂PH₂)], RcCH₂PH₂ and Fc(CH₂)₆PH₂∙BH₃, phosphane oxide, FcCH₂P(O)H₂, and phosphinic acid, FcCH₂P(O)(OH)H, were also synthesised and reported. The X-ray crystal structures of Fc(CH₂)₆PH₂∙BH3 and FcCH₂SeCN are also presented in the present thesis. The stability of the hydrides of heavier p-block main group elements with a ferrocenyl or ruthenocenylalkyl moiety under ambient conditions has been investigated using NMR and/or IR spectroscopy. Ferrocenylalkyl and ruthenocenylmethyl primary phosphanes, Fc(CH₂)nPH₂ (n = 4, 6 or 11) and RcCH₂PH₂, respectively, exhibited a remarkable stability towards air oxidation in solution, i.e. ~1 year. In contrast, the secondary phosphanes were not as stable as expected, rapidly oxidising over several weeks or months. General trend for the oxidative stability of the secondary phosphanes could not be elucidated on the basis of the electronegativity, size or degree of conjugation of the substituent on the phosphorus. Ferrocenylmethyl primary arsane, FcCH₂AsH₂, was also unexpectedly air-sensitive, having been readily oxidised as a neat liquid or in solution upon the exposure to air. Ferrocenylethyl primary silane, Fc(CH₂)₂SiH₃, was stable both as a neat liquid and also in solution. It could be purified on a TLC plate in air and also stored in solution for up to 7 months. On the other hand, ferrocenylmethyl primary germane, FcCH₂GeH₃, was unstable, almost completely decomposing left overnight in solution, which was indicated by the disappearance of the germane proton NMR signal by ¹H NMR spectroscopy. Ferrocenylalkyl selenols, Fc(CH₂)nSeH (n = 1 or 4), were both found to be unstable as neat liquids or in solution. Handling the compounds in air caused significant oxidation, resulting in the formation of the corresponding diselenides which are the common oxidation products of selenols. Ferrocenylmethyl selenol, FcCH₂SeH, was completely oxidised in solution in air in 5 days while ferrocenylbutyl selenol, Fc(CH₂)₄SeH, in 3 days. The rapid oxidation of the latter was also observed by IR spectroscopy over a period of 10 minutes when exposed to air as a neat liquid. The oxidative stability of the air-sensitive primary phosphanes, PhPH₂ and camphylPH₂, in the presence of ferrocene, FcH, or its derivative, FcCH₂PH₂, in solution, was studied by ³¹P NMR spectroscopy. The study showed that the primary phosphanes could be stabilised by simple addition of FcH or FcCH₂PH₂. The corresponding ³¹P NMR study using known antioxidants, diphenyl picryl hydrazyl (DPPH) or nitrosobutane, in place of the ferrocene species also exhibited that PhPH₂ could be stabilised by addition of an antioxidant. These results suggest that FcH and FcCH₂PH₂ can be used to stabilise air-sensitive primary phosphanes in solution by simply adding them, probably acting as radical scavengers.

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  • Cyclorheniated Azabutadienes and Their Reactions with Unsaturated Molecules

    Asamizu, Toshie (2009)

    Masters thesis
    University of Waikato

    This thesis reports the studies on the reaction of 1-azabutadienes with PhCH2Re(CO)5 to prepare the cyclometallated azabutadiene tetracarbonyl compounds. Three 1-azabutadienes with different reactivity on the N and C-1 carbons were prepared and their reactions with PhCH2Re(CO)5 were investigated. All the reactions gave a mixture of the cyclorheniated azabutadienes and the isomers of the substituted derivatives formed by substitution by a second azabutadiene. The substituted derivatives as the mixture were always the main products of the reactions and were obtained in good-to-excellent yield even under modified conditions intended to optimise the yield of the cyclorheniated azabutadienes. The yield could not be improved beyond 30 %. Isomerisation of the azabutadiene about the N=C bond provided very rare cis-azabutadiene metal complexes. NMR studies on the mixture of the two isomers and suggested that the product ratio depended on the molar ratio of PhCH2Re(CO)5 in the reaction mixtures. The reactions gave the Re analogues of the products obtained in the corresponding Mn reactions. All the compounds were characterised spectroscopically as well as by microanalysis and examples of all three types were structurally determined by X-ray crystallography. The reactions of the substituted derivative as the mixture of the two isomers with unsaturated molecules including phenyl acetylene, p-methoxyphenyl isocyanide, and phenyl isocyanate and methyl acrylate were investigated.

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  • Cyclorhenated compounds derived from 1,4-diaryl-1-azabutadienes: preparation, structures and reactions

    Asamizu, Toshie; Nielsen, Jaime L.; Nicholson, Brian K. (2010)

    Journal article
    University of Waikato

    PhCH₂Re(CO)₅ reacted with 1,4-diaryl-1-azabutadienes to give cyclometallated (η²-(C,N)-azabutadiene)Re(CO)₄ (4) together with the substituted derivatives (η¹-(N)-azabutadiene)(η²-(C,N)-azabutadiene)Re(CO)₃ (6 and 7) The substituted product was shown by NMR and X-ray crystal structure analysis to be an inseparable mixture of isomers differing in the conformation of the η¹-ligand about the N C bond—trans for (6) and cis for (7). Reaction of the mixture of 6 and 7 from 1,4-diphenyl-1-azabutadiene with phenyl acetylene gave η⁵-(1,2,4-triphenyl-1-aza-cyclohexadienyl)Re(CO)₃.

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