Magnetic Properties of Radical, Crystalline Mixed Cyclopentadienyl/Dithiolene Complexes

Abstract

This chapter describes in detail a class of heteroleptic complexes associating cyclopentadienyl (Cp) and dithiolene (dt) ligands, essentially known with the Cp2M(dt), CpM(dt)2, [CpM(dt)]2 and CpM(dt) stoichiometries. The three first classes are reported with early transition metals (groups 4−7), while the latter is restricted to group 9 and 10 metal centers. Depending on the metal and the complex oxidation state, paramagnetic species can be isolated, as for example the formally d 1 species Cp2V(dt), [Cp2Mo(dt)]+ or [CpMo(dt)2], or the formally d 7 CpNi(dt). They all exhibit a rich structural chemistry and variable spin density distribution between Cp, M and dt fragments. Their magnetic properties in the solid state are a combination of an original spin density distribution and specific intermolecular interactions in the crystalline phase. They lead to a variety of behaviors, from independent spins with their associated Curie-type law, singlet-triplet systems and their extension to alternated spin chains and spin ladders, uniform spin chains or ordered antiferromagnetic ground states. Besides the S• • •S and S• • •M interactions which control most of the antiferromagnetic interactions observed so far in these magnetic organometallic complexes, the contribution of direct Cp• • •Cp and Cp• • •S interactions is shown to control in some cases the magnetic behavior of the complexes, an original feature in organometallic chemistry.