The kinetics and mechanism of polymerization of acetylene by rare earth coordination catalysts

The rare earth coordination catalysts are cis-directing catalysts for the polymerization of acetylene. To get more insight into the features of these catalysts, a kinetic study was carried out. The polymerization rate could be expressed as $\text{R}{}_{\mathrm{<mtext>p</mtext>}}\text{= K}{}_{\mathrm{<mtext>p</mtext>}}\text{[}\text{M}\text{][}\text{C}{}^1\text{]}$. The effects of different catalysts with various rare earth elements on kinetics were studied, and the following activity sequence was found: Nd>Gd>La>Y～Er>Lu>Sc. The ligands attached to rare earth elements greatly affected the polymerization activities of catalysts. The mechanism of acetylene polymerization by rare earth coordination catalysts was discussed on the basis of the experimental results.     

Al2O3 coated α-Fe solid solution nanocapsules prepared by arc discharge

Al₂O₃ coated α-Fe solid solution nanocapsules are prepared by arc-discharging a bulk AlNiCo permanent magnet. The size of the nanocapsule is in range of 3–300 nm and the thickness of the shell is 1–6 nm. Al atoms in the AlNiCo magnet form the shell of amorphous Al₂O₃ to prevent the nanocapsules from further oxidation. The magnetic properties of saturation magnetization J_s=85 A m²/kg and coercive force ${}_{\mathrm{j}}\text{H}{}_{\mathrm{<mtext>c</mtext>}}\text{=27.5}$ kA/m are achieved for the nanocapsules.     

Intercalation of graphite by silicon tetrafluoride and fluorine to yield a second-stage salt C24SiF5

Powdered graphite (either finely broken HOPG or Union Carbide SP1) interacts with 1:1 SiF₄/F₂ mixture (～50 atmospheres) at 40°, to yield a second-stage compound (a₀ = 2.46(1), c₀ = 11.29(1) Å) of composition C～₂₄SiF₅. This product interacts with excess PF₅ with quantitative displacement of SiF₄ to yield a first-stage fluorophosphate (a₀ = 2.46(1); $\text{c}{}_0\text{= 7.65(1)}\text{A}\text{?}\text{)}$ according to the equation: C₂₄SiF₅ + 2PF₅ → C₂₄PF₆. PF₅ + SiF₄. The first-stage fluorophosphate falls to a second-stage salt (a₀ = 2.46(1); $\text{c}{}_0\text{= 10.87}\text{A}\text{?}\text{)}$ under vacuum: $\text{C}{}_{24}\text{PF}{}_6\text{.}\text{PF}{}_5\text{20°}\text{→}\text{C}{}_{24}\text{PF}{}_6\text{+}\text{PF}{}_5$. This is identical to that prepared directly: $\text{24}\text{C}\text{+}\text{PF}{}_5\text{+}\text{1}\text{2}\text{F}{}_2\text{→}\text{C}{}_{24}\text{PF}{}_6$. Extensive reduction of C₂₄PF₆, at ≈20° : 2C₂₄PF₆ + PF₃ → 48C + 3PF₅ to graphite of crystallinity comparable to that of the starting graphite establishes that the initial C₂₄SiF₅ does not involve extensive fluorination of the graphite. The ease of displacement of SiF₄ by superior fluoroacids indicates that C₂₄SiF₅ can be a valuable precursor for other graphite salts. Ready formation of a first-stage fluoroborate, $\text{C}{}_7\text{BF}{}_4\text{, I}{}_{\mathrm{<mtext>c</mtext>}}\text{= 7.70(1)}\text{A}\text{?}$ contrasts with the failure to prepare similarly a first-stage SiF₅^? salt.     

New conductive polymeric materials: Cofacial assembly of mixed valent metallomacrocycles

This paper reports on an approach to control molecular stacking interactions in low-dimensional mixed valence materials by locking partially oxidized metallomacrocycles together in a cofacial orientation. Iodine doping of the face-to-face linked oligomers [M(Pc)O]_n (M = Si, Ge, Sn; Pc = phthalocyaninato) produces electrically conductive polymers {[M(Pc)O]I_xn with a wide range of x stoichiometries. Resonance Raman spectroscopy indicates that the iodine has oxidized the polymer chain. Polymer structure has been studied by X-ray powder diffraction, and it is possible to estimate interplanar spacings. Halogen doping of the [M(Pc)O]_n materials is accompanied by electrical conductivity increases as large 10⁷ (ohm cm)^?1; the general trend is $\text{σ}{}_{\mathrm{<mtext>Si</mtext>}}\text{? σ}{}_{\mathrm{<mtext>Ge</mtext>}}\text{> σ}{}_{\mathrm{<mtext>Sn</mtext>}}$. Variable temperature conductivity and magnetic susceptibility data are reported.