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 pentamethylcyclopentadienyl rhodium chloride with fullerene C-60 in different reduction states have been obtained in crystalline forms. Reduction of {Cp*Rh-III(mu-Cl)Cl}(2) dimer in the presence of C-60 by excess NaBPh4 yields binuclear complex [{Cp*Rh-II(mu-Cl)}(2)(eta(2),eta(2)-C-60)].C6H14 (1) in which two Cp*Rh units bridged by two mu-Cl anions are coordinated to two 6-6 bonds of C-60 belonging to one hexagon. No essential charge transfer from metal to C-60 is observed in 1. Complex 1 is EPR-silent most probably due to strong antiferromagnetic coupling of Rh-II through the mu-Cl and fullerene bridges. Interaction of (Bu4N+)(C-60.-) and (Bu4N+){(VO)-O-IV(Pc.(3)-)}.- salts with {Cp*Rh-III(mu-Cl)Cl-2}(2) yields anionic (Bu4N+){Cp*RhCl(eta(2)-C-60)}-.0.75C(6)H(4)Cl(2) complex (2) in which only one Cp*RhCl fragment is coordinated to the 6-6 bond of C-60. According to magnetic measurements, the {Cp*(RhCl)-Cl-I(eta(2)-C-60)}- anions in 2 contain diamagnetic Rh-I and neutral eta(2)-C-60 at low temperatures (T < 120 K). Above this temperature, charge transfer (CT) from RhI to eta(2)-C-60 is realized with the formation of paramagnetic negatively charged eta(2)-C-60 and RhII species. This process is accompanied by the appearance of two broad EPR signals with g(1) = 2.0353 and the line width Delta H = 38.2 mT and g(2) = 2.3149, and Delta H = 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 mu(B) at 300 K. This value is intermediate between 1.73 and 2.45 mu(B), which is characteristic of systems with one and two noninteracting S = 1/2 spins, respectively.