- Ferromagnetic Behavior of .+.+. Structural and Magnetic Characterization of Decamethylferrocenium Tetracyanoethenide, .+.+*MeCN, and Decamethylferrocenium Pentacyanopropenide, .+-
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The reaction of decamethylferrocene, Fe(C5Me5)2, and tetracyanoethylene, TCNE, leads to the isolation of two products: .+.+ and .+-.Crystals of the .+ salt as the MeCN solvate belong to the monoclinic C2/c space group = 16.250 (3) Angstroem; b = 10.415 (2) Angstroem, c = 32.851 (9) Angstroem, β = 101.76 (2)deg, Z = 8, V = 5443 Angstroem3>.The salt's linear chain motif is comprised of alternating S = 1/2 cations and S = 1/2 anions.The C5 ring .+ separation is 3.51 Angstroem, whereas the intrachain Fe(III)-Fe(III) separation is 10.415 Angstroem.The cation's average Fe-C, C-C, and C-Me distances of 2.086, 1.410, and 1.499 Angstroem agree with similar structural determinations.The .+ metric parameters are reported for the first time: central C-C, C-CN, and CN distances are 1.392 (9), 1.417 (2), amd 1.140 (4) Angstroem, respectively.The NC-C-CN angle is 117.7 deg.MeCN is lost upon isolation of the crystals, and the lattice transforms into an orthorombic Cmc21 lattice.This desolvated complex can be prepared from THF and possesses chains of alternating cations and disordered anions.Adjacent chains are in-registry and out-of-registry as observed for the MeCN solvate.The - salt belongs to the same space group = 13.950 (2) Angstroem, b = 14.160 (2) Angstroem, c = 12.870 (2) Angstroem, β = 100.35 (1)deg, Z = 4, V = 2501 Angstroem3>, and the motif is comprised of alternating S = 1/2 cations and S = 0 anions.The C5-- separation is 3.44 Angstroem, and the intrachain Fe(III)-Fe(III) separation is 10.305 Angstroem.The cations average Fe-C, C-C, and C-Me separations are 2.095, 1.423, and 1.501 Angstroem, respectively.The anions average C-C, C-CN, and CN distances are 1.396 (2), 1.433, and 1.147 Angstroem, respectively.The C-C-C, NC-C-CN, and NC-C-C angles are 129.7, 116.6, and 115.2 deg, respectively.The magnetic properties of these salts were measured via the Faraday technique.Above 2 K the antiferromagnetic .+- and +.+ salts obey the Curie-Weiss expression, χ = C/(T-Θ), with a small Θ(+.-:θ = -1.0 +/- 0.3 K; μeff (calculated from 2.83(χT)1/2 from the higJ temperature data) = 1.72 μB; .+-:Θ = -1.2 +/- 0.4 K; μeff = 2.99 μB).In contrast, above 60 K the .+.- salt is ferromagnetic as it obeys the Curie-Weiss expression with Θ = +30 K; μeff evaluated at 300 K is 3.10 μB.The saturation magnetization of polycrystalline samples of the .- salt at 4.2 K is 1.1 +/- 0.1E4 emu*G/mol for 300 G 17 K susceptibility data fit a 1-D S = 1/2 Heisenberg ferromagnetic model.Below 5 K the charge-transfer salt displays the onset of spontaneous magnetization in zero applied field consistent with a 3-D (bulk) ferromagnetic ground state.For .+.- the 57Fe Moessbauer spectra exhibit a narrow singlet (Γ ca. 0.323 mm/s) with an isomer shift of 0.427 mm/s at..
- Miller, Joel S.,Calabrese, Joseph C.,Rommelmann, Heiko,Chittipeddi, Sailesh R.,Zhang, Jian H.,et al.
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