121192-65-2Relevant articles and documents
Crystal Structures and Phase Sequences of Metallocenium Salts with Fluorinated Anions: Effects of Molecular Size and Symmetry on Phase Transitions to Ionic Plastic Crystals
Mochida, Tomoyuki,Funasako, Yusuke,Ishida, Mai,Saruta, Shingo,Kosone, Takashi,Kitazawa, Takafumi
, p. 15725 - 15732 (2016/10/25)
Sandwich compounds often exhibit various phase transitions, including those to plastic phases. To elucidate the general features of the phase transitions in metallocenium salts, the thermal properties and crystal structures of [Fe(C5Me5)2]X ([1]X), [Co(C5Me5)2]X ([2]X), and [Fe(C5Me4H)2]X ([3]X) have been investigated, where the counter anions (X) are Tf2N (=(CF3SO2)2N?), OTf (=CF3SO3?), PF6, and BF4. The Tf2N salts commonly undergo phase transitions from an ordered phase at low temperatures to an anion-disordered phase, followed by a plastic phase and finally melt at high temperatures. All these salts exhibit a phase transition to a plastic phase, and the transition temperature generally decreases with decreasing cation size and increasing anion size. The crystal structures of these salts comprise an alternating arrangement of cations and anions. About half of these salts exhibit phase transitions at low temperatures, which are mostly correlated with the order–disorder of the anion.
Ferromagnetic behavior in linear charge-transfer complexes. Structural and magnetic characterization of octamethylferrocene salts: [Fe(C5Me4H)2]?+[A] ?- (A = TCNE, TCNQ)
Miller, Joel S.,Glatzhofer, Daniel T.,O'Hare, Dermot M.,Reiff, William M.,Chakraborty, Animesh,Epstein, Arthur J.
, p. 2930 - 2939 (2008/10/08)
The reaction of FeII(η5-C5Me4H)2 with cyano acceptors A {A = TCNE (tetracyanoethylene), TCNQ (7,7,8,8-tetracyano-p-quinodimethane), n-C4(CN)6 (n-hexacyanobutadiene), C6(CN)6 [tris(dicyanomethylene)cyclopropane], DDQ (2,3-dichloro-5,6-dicyanobenzoquinone), TCNQF4 (perfluoro-7,7,8,8-tetracyano-p-quinodimethane)} results in formation of 1:1 charge-transfer salts of [FeIII(C5Me4H)2] ?+[A]?- composition. The TCNE and TCNQ complexes have been structurally characterized. The [FeIII-(C5Me4H)2] ?+[TCNE]?- salt belongs to the centrosymmetric Cmca space group [a = 14.990 (3) A?, b = 11.580 (7) A?, c = 12.503 (4) A?, Z = 4, T = 23°C, V = 2170 (3) A?3, Ru = 0.037, Rw = 0.040]. The anion exists as isolated planar [TCNE]?- radicals. The C-C, C-CN, and C≡N bonds are 1.385 (6), 1.426 (4), and 1.135 (5) A?, respectively, and the NC-C-CN, NC-C-C, and N≡C-C angles are 118.7 (4), 120.6 (4), and 179.6 (4)°, respectively. The [FeIII(C5Me4H)2] ?+[TCNQ]?- salt belongs to the centrosymmetric P1 space group [a = 8.636 (1) A?, b = 9.574 (3) A?, c = 10.025 (4) A?, α = 63.77 (3)°, β = 70.22 (2)°, γ = 162.79 (2)°, Z = 1, T = 23°C, V = 651.6 (3), Ru = 0.052, Rw = 0.054]. The anion exists as isolated planar [TCNQ]?- radicals. The HC-CH, HC-C, C-C(CN)2, C-CN, and C≡N bonds are 1.358, 1.419, 1.405, 1.417, and 1.148 A?, respectively, and the HC-C(H)-C, HC-C-CH, NC-C-CN, NC-C-C, and N≡C-C angles average 121.6, 116.7, 115.6, 122.1, and 178.9°, respectively. The solid-state structure for both salts consists of linear chains of ?D?+A?-D?+A ?-D?+?. The cation for both salts has a staggered conformation with the Fe asymmetrically bonded to the C5 ring; i.e., the average Fe-CH and Fe-CMe separations are 2.057 and 2.099 A?, respectively. The Fe-C5 ring centroid distance is 1.694 A? for the [TCNE]?- salt and is 1.710 A? for the [TCNQ]?- salt. The high-temperature magnetic susceptibility for polycrystalline samples of these complexes can be fit by the Curie-Weiss law, χ = C(T - θ)-1, with θ = +0.5 ± 2.2 K, and μeff ranges from 2.71 to 3.97 μB, suggesting that the polycrystalline samples measured had varying degrees of orientation. The 7.0 K EPR spectrum of the radical cation exhibits an axially symmetric powder pattern with g∥ = 4.11 and g⊥ = 1.42, and the EPR parameters are essentially identical with those reported for ferrocenium and decamethylferrocenium. No EPR spectrum is observed at 78 K. Akin to the [Fe(C5Me5)2]?+ salts, these salts have 57Fe Mo?ssbauer spectra consistent with complete charge transfer; however, unlike the case for the former complexes, quadrupole splittings of 0.30 and 0.22 mm/s are observed at 4.8 and 298 K, respectively. The absence of strong interionic magnetic coupling for the [Fe(C5Me4H)2]?+ salts contrasts with the behavior of the [Fe(C5Me5)2]?+ salts.
