Use of a cubane-type Mo3 CoS4 molecular cluster as paramagnetic unit in the synthesis of hybrid charge-transfer salts

Abstract

Selective substitution of the chlorine atom coordinated to cobalt in the paramagnetic Mo₃(CoCl)S₄(dmpe)₃Cl₃ (dmpe = 1,2-bis(dimethylphosphanyl) ethane) complex with a S = 1/2 ground state has been achieved by iodine oxidation to afford the also paramagnetic [Mo₃(CoI)S₄(dmpe)₃Cl₃]I ([1]I) salt with a S = 1 ground state in almost quantitative yield. Replacement of chorine by iodine has no significant effect on the structural and electrochemical properties of the Mo₃CoS₄ system. Metathesis of the [1]I salt with the paramagnetic nickel anionic dithiolate [Ni(mnt)₂]^- (mnt = maleonitrilodithiolate) affords [1]₂[Ni(mnt)₂]. The stoichiometry evidenced by X-ray analysis reveals that reduction of the [Ni(mnt)₂]^- radical to the corresponding diamagnetic closed shell [Ni(mnt)₂]^2- dianion, presumably via dismutation, has occurred during the metathesis process. The crystal structure of [1]₂[Ni(mnt)₂] consists of [Ni(mnt)₂]^2- dianions sandwiched by two cluster 1⁺ cations which yield {1⁺·[Ni(mnt)₂]^2-·1⁺} subunits arranged along the crystallographic c axis. Magnetic susceptibility measurements for [1]₂[Ni(mnt)₂] show a χT product of 0.99 emu K/mol largely unchanged in the 10-300 K range. This behavior agrees with the presence of an S = 1 cluster 1⁺ cation while the Ni(mnt)₂ moiety does not contribute to the paramagnetism of the sample. © 2010 Elsevier B.V. All rights reserved.