Synthesis and Magnetic Properties of 1:1 Salts containing the Bis(η6-hexamethylbenzene)cobalt Cation

Article abstract of DOI:10.1039/DT9930003071

The salts 6-C6Me6)2>(+)>(-) (A = BPh4, NbF6, PF6 or SbF6) have been prepared from anhydrous CoCl2.Solid-state magnetic susceptibility measurements on these salts indicate that they all obey the Curie-Weiss law in the temperature range 30-300 K with μ_eff = 2.7, 2.8, 2.8 and 2.6 μ_B with corresponding θ values of -1.4, 0.2, -4.1 and 0.4 K for the BPh4(-), NbF6(-), PF6(-) ad SbF6(-) salts respectively.Below 20 K, the magnetic susceptibility for all the salts deviate substantially from the Curie-Weiss law.The experimental susceptibility data for the compounds 6-C6Me6)2>(+)(-) and 6-C6Me6)2>(+)(-) can be fitted to a model in which the ³Ag_2g triplet ground state assigned to the 6-C6Me6)2>(+) moiety exhibits a positive zero-field splitting of 17.8 and 20.5 cm^-1 respectively.In contrast, the magnetic susceptibilities for 6-C6Me6)2>(+)>(-) (A = PF6 or SbF6) cannot be fitted to this model in the range 2-30 K due to more significant intermolecular antiferromagnetic spin-spin interactions.All the salts were EPR silent at between 4 and 300 K both in the solid state and in frozen solution.Reaction of 6-C6Me6)2>(+)(-) with either (tcnq = tetracyano-p-quinodimethane) or 3> 3 = tris(dicyanomethylene)cyclopropane> gave insoluble paramagnetic precipitates with μ_eff = 4.1 and 4.5 μ_B and θ values of -12.9 and -3.5 K respectively.

Full text of DOI:10.1039/DT9930003071

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