4 years ago

Coordination Complexes of Fullerene C60 with Rhodium {Cp*RhII(μ-Cl)}2(η2,η2-C60) and (Bu4N+){Cp*RhICl(η2-C60)}−. Temperature-Induced Charge Transfer from RhI to η2-C60

Coordination Complexes of Fullerene C60 with Rhodium {Cp*RhII(μ-Cl)}2(η2,η2-C60) and (Bu4N+){Cp*RhICl(η2-C60)}−. Temperature-Induced Charge Transfer from RhI to η2-C60
Sergey I. Troyanov, Rimma N. Lyubovskaya, Dmitri V. Konarev, Hideki Yamochi, Hiroshi Kitagawa, Akihiro Otsuka, Alexey V. Kuzmin, Salavat S. Khasanov
Coordination complexes of pentamethylcyclopentadienyl rhodium chloride with fullerene C60 in different reduction states have been obtained in crystalline forms. Reduction of {Cp*RhIII(μ-Cl)Cl}2 dimer in the presence of C60 by excess NaBPh4 yields binuclear complex [{Cp*RhII(μ-Cl)}222-C60)]·C6H14 (1) in which two Cp*Rh units bridged by two μ-Cl anions are coordinated to two 6–6 bonds of C60 belonging to one hexagon. No essential charge transfer from metal to C60 is observed in 1. Complex 1 is EPR-silent most probably due to strong antiferromagnetic coupling of RhII through the μ-Cl and fullerene bridges. Interaction of (Bu4N+)(C60•–) and (Bu4N+){VIVO(Pc•3–)}•– salts with {Cp*RhIII(μ-Cl)Cl2}2 yields anionic (Bu4N+){Cp*RhCl(η2-C60)}·0.75C6H4Cl2 complex (2) in which only one Cp*RhCl fragment is coordinated to the 6–6 bond of C60. According to magnetic measurements, the {Cp*RhICl(η2-C60)} anions in 2 contain diamagnetic RhI and neutral η2-C60 at low temperatures (T < 120 K). Above this temperature, charge transfer (CT) from RhI to η2-C60 is realized with the formation of paramagnetic negatively charged η2-C60 and RhII species. This process is accompanied by the appearance of two broad EPR signals with g1 = 2.0353 and the line width ΔH = 38.2 mT and g2 = 2.3149, and ΔH = 37.0 mT at room temperature whose integral intensities increase with temperature. Estimated activation energy of CT is 473 ± 7 K. Effective magnetic moment of 2 also increases with temperature, attaining 2.16 μB at 300 K. This value is intermediate between 1.73 and 2.45 μB, which is characteristic of systems with one and two noninteracting S = 1/2 spins, respectively.

Publisher URL: http://dx.doi.org/10.1021/acs.organomet.7b00660

DOI: 10.1021/acs.organomet.7b00660

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