| Popis: |
The reaction of donor, Cr(arene)2 (arene = C6Me6 and C6Me3H3), D, with the acceptor TCNQ, A, results in formation of electron-transfer salts of [D].+[A].- composition. Two phases of [Cr(C6Me3H3)2] .+[TCNQ].- have been structurally characterized. The α-phase belongs to the centrosymmetric C2/c space group [a = 14.014 (4) Å, b = 16.347 (4) Å, c = 22.964 (6) Å, β = 107.44 (2)°, Z = 8, V = 5019 (5) Å3, T = 23°C, R = 0.082] with the solid-state structure consisting of ⋯D.+D.+A22-D .+D.+⋯ linear chains. Each [TCNQ]- in the [TCNQ]22- dimer is planar, and the intradimer separation is 3.47 Å. The anion-anion overlap is unusual as the dihedral angle between the planes normal to the long molecular axes is 31°. The β-phase crystallizes in the P21/c space group [a = 9.588 (5) Å, b = 16.390 (3) Å, c = 8.419 (6) Å, β = 106.84 (6)°, Z = 2, V = 1266 (9) Å3, T = 23°C, R = 0.044] with the solid-state structure consisting of ⋯D.+A.-D.+A.-⋯ linear chains. The magnetic susceptibility of α- [Cr(C6Me6)2] [TCNQ] obeys the Curie-Weiss law with an effective moment, μeff, of 1-77 μB and θ of -0.1 K. This is consistent with the presence of a diamagnetic [TCNQ]22- dimer (v(C≡N) = 2156 m, 2175 s, and 2182 s cm-1). In contrast, [Cr(C6Me3H3)2][TCNQ] does not obey the Curie-Weiss law but can be fit to an expression that accounts for contributions from independent Curie spins for the cation and a thermally activated triplet state for the dimerized anions [ΔE = 315 K, 0.027 eV, 219 cm-1, 0.44 kcal/mol]. © 1990 American Chemical Society. |
