Research On Syntheses, Structures And Properties Of Radical Cations Containing Nitrogen, Phosphorous And Cobalt

Radicals are atoms, molecules or ions with unpaired electrons, which have attracted great attention of chemists since the proof of triphenylmethyl radical in 1900. Nowadays, the radical chemistry has become a strong branch of modern chemistry. The stable radicals have both open shell structure and chemical stability, not only play key roles in understanding the effect of radicals in reaction mechanisms and structural chemistry, but also show unique magnetic, conductivity, electronic and nonlinear optical properties, and have drawn extensive concern of people who are engaged in chemistry, biology, medicine and material science. This thesis summarized the synthesis and characterization of radical cations containing N, P and Co atoms using weakly coordinating anions as the counter anions. The main results are introduced as follows:（1） A methylene-bridged triphenylamine has been oxidized to plannar radical cation by B（C₆F₅）₃ or Ag[Al（OC（CF₃）₃）₄]. Further reaction of the radical cation and the methylene-bridged triphenylamine with trace amounts of Ag[Al（OC（CF₃）₃）₄] resulted in a dication, providing a rare example of structurally characterized bis（triarylamine） "biplarons". The dication can be directly prepared by the bis（triarylamine） and 2 equiv of Ag[Al（OC（CF₃）₃）₄]. X-ray structural analysis,1H NMR and UV-vis together with theoretical calculations indicating the singlet diradical character of the diradical dication and is analogous to Chichibabin’s hydrocarbons.（2） A radical cation with planner [NP]2 four membered ring was obtained by one-electron oxidation of the neural molecule by NOSbF₆. The structure of the radical cation was characterized by EPR spectroscopy, UV-vis spectroscopy and single-crystal X-ray diffraction. EPR and DFT calculations show that the spin density mainly resides on the phosphorus and nitrogen atoms of the [NP]2 ring. The bond lengths and bond angles in the [NP]2 ring of the radical cation are tend to equal compared to those of neutral molecule, because of the further electron density delocalization of the radical cation. The isolation and characterization of the [NP]2 radical cation provide ideas for the synthesis and characterization of new four-member radical cations of the phosphorus family.（3） Metalloradical cations of [Co₂Fv（CO）₄]’+and [Co₂Cp2（CO）₄]·+ （Fv= fulvalenediyl, Cp=η5-C5H5） formed by oxidations of piano-stool cobalt carbonyl complexes of Co₂Fv（CO）₄ and CpCo（CO）₂ by Ag[Al（ORF）₃]4 [ORF=OC（H）（CF₃）₂ or OC（Me）（CF₃）₂]. The radical cations can be stabilized with weakly coordinating anions in the solid state. They feature a suppoted and an unsupported cobalt-cobalt three- electron σ-bond, respectively, each with a formal bond order of 0.5 （hemi bond）. When Cp is replaced by bulkier Cp* （Cp*=η-C5Me5）, an interchange between an unsupported radical cation [Co₂Cp*2（CO）₄]·+ and a supported radical cation [Co₂Cp*2（μ-CO）₂（CO）₂]·+is observed in solution, which crystallize out simultaneously and co- crystallize in the solid state. The [Co₂Cp*2（CO）₄]·+ features an unsupported metal-metal hemi-bond, and there is no bond between two Co atoms of [Co₂Cp*2（μ-CO）₂（CO）₂]·+ indicated by DFT calculation.（4） The lithium salt of Li[Al（OC（CCl3）（CF₃）₂）₄]has been synthesized with LiAIH4 and HO-C（CC13）（CF₃）₂ as the starting materials. The Li[Al（OC（CCl3）（CF₃）₂） 4] is soluble in polar and non-polar solvents, its solubility in n-hexane confirms it may be an candidate for Li+ catalysis. Compared with the high solubility of this lithium salt, the solubility of analogous lithium salt Li[Al（OC（CF₃）₃）₄] is poor in polar solvents or non-polar solvents. The single-crystal X-ray diffraction show that the Li[Al （OC（CC13）（CF₃）₂）₄] salt consists of a six coordinated Li+ cation, coordinating a [Al（OC（CCl3）（CF₃）₂）₄] anion that serves as hexadentate O2F₂C12 ligand; while the Li[Al（OC（CF₃）₃）₄] salt consists of a seven coordinated Li+ cation, coordinating a [Al（OC（CF₃）₃）₄]-anion that serves as hexadentate O2F4 ligand and a bridging F of a second anion and formed a polymer structure by intermolecular F…Li interaction. Thus the structure and larger volume may be the favorable factors for the high solubility of Li[Al（OC（CCl3）（CF₃）₂）₄] salt. The lithium salt of Li[Al（OC（CCl3）（CF₃）₂） 4] react with ClC（Ph）₃ affords the stable [CPh3]+salt of [CPh3] [Al（OC（CCl3）（CF₃）₂） 4].