The Concentration Control of Magnetic Fullerene C₆₀^•‐ Radical Anions in a Crystal Lattice of the (Bu₄N⁺)₂{(C₆₀^•‐)⋅C₆H₄Cl₂}_x{[CpMo(CO)₂C₆₀]⁻}_2‐x (x=1, 0.74) Complexes

Abstract

Interaction of the (Bu4N+)(C60•‐) salt with {CpMo(CO)3}2 at a different molar ratio allows one to obtain isostructural (Bu4N+)2{(C60•‐)⋅C6H4Cl2}x{[CpMo(CO)2C60]−}2‐x complexes with x=1 (1) and 0.74 (2). The complexes contain the solvated C60•‐ radical anions and the coordination [CpMo(CO)2C60]− anions which share one position in the crystal structure with different occupancies. Molybdenum atom coordinates by the η2‐type to the 6–6 bond of C60 in the [CpMo(CO)2(η2‐C60)]− anions. The length of the Mo−C(C60) bonds is 2.241(6)‐2.244(6) Å. Optical spectrum of 1 supports the presence of uncoordinated C60•‐ and neutral coordinated C60 in [CpMo(CO)2(η2‐C60)]−. Paramagnetism of C60•‐ in 1 provides effective magnetic moment of 1.2 μB whereas coordination [CpMo(CO)2(η2‐C60)]− anions are diamagnetic and EPR silent. Fullerenes form closely packed double ribbons with triangular fullerene lattice. 1 shows antiferromagnetic coupling of spins with a small Weiss temperature of −7 K. That can be explained by magnetic dilution of paramagnetic C60•‐ species by diamagnetic [CpMo(CO)2(η2‐C60)]− anions.