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The η2 Complex of Nickel Bis(diphenylphosphanyl)propane with Fullerene: {Ni(dppp)(η2-C60)}·(Solvent) Obtained by Reduction



The η2 complex of nickel bis(diphenylphosphanyl)propane with fullerene, {Ni(dppp)(η2-C60)}·(C6H14)0.84·(C6H4Cl2)0.16 (1) (C6H14: hexane, C6H4Cl2: o-dichlorobenzene), has been obtained by reduction of the Ni(dppp)Cl2 and C60 mixture with sodium fluorenone in o-dichlorobenzene and slow precipitation of the single crystals by diffusion of hexane. Nickel coordinates to the 6–6 bond of C60 by η2-coordination to form Ni–C(C60) bonds with a length of 1.948–1.951(2) Å, which are the shortest M–C bonds among known η2 complexes of fullerenes. The 6–6 bond length [1.488(3) Å] where the Ni atom is coordinated is noticeably longer than the average length of other 6–6 bonds in C60 [1.388(2) Å]. Coordination of nickel to C60 results in the splitting of two bands for two IR-active modes of C60 into three bands, because of the lower symmetry of C60, and a noticeable shift in the F1u(4) mode of C60 to lower frequencies, as a result of π back-donation. The dark green complex manifests two absorption bands at 664 and 890 nm in the visible range. The complex is EPR silent since only a weak narrow signal with g = 2.0000 and ΔH = 0.17 mT was found in the EPR spectrum of 1 at room temperature, which originates from about 0.1 % of spins of the total amount of C60.