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DOI: 10.1039/A701161J (Paper) Reference Section for: J. Chem. Soc., Dalton Trans., 1997, 2403-2408

Synthesis, structural and magnetic characterisation of the electron-transfer salts [Fe2(η-C5Me5)2 (µ-SEt)2(CO)2]2[tcnq] 2 and [Fe2(η-C5Me5)2 (µ-SEt)2(CO)2][tcne] (tcnq = 7,7,8,8-tetracyanoquinodimethane; tcne = tetracyanoethylene)

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Riaan Büchner, John S. Field and Raymond J. Haines

Abstract

Reaction of the electron-rich thiolate-bridged complex [Fe2(η-C5Me5)2(µ- SEt)2(CO)2] with 1 molar equivalent of the electron-acceptor compounds 7,7,8,8-tetracyanoquinodimethane (tcnq) and tetracyanoethylene (tcne) is accompanied by electron transfer and resulted in the formation of the dark green crystalline salts [Fe2(η-C5Me5)2(µ- SEt)2(CO)2]2[tcnq]2 1 and [Fe2(η-C5Me5)2(µ- SEt)2(CO)2][tcne] 2 respectively. The crystal structures of these salts have been determined by X-ray diffraction methods and the cations thereof established to have very similar stereochemistries. The C5Me5 ligands are cis disposed with respect to the Fe · · ·[hair space] [hair space]Fe vector with the dihedral angles between their planes being 71 and 68° for 1 and 2 respectively. The Fe · · ·[hair space] [hair space]Fe distances are respectively 3.077(2) and 3.069(2) Å. Crystals of 1 consist of isolated units of composition D˙+(A)22-D˙ where D˙+ denotes the cation and (A)22- a (tcnq)22- dimer, the planes of the tcnq moieties comprising the dimer and those of the adjacent C5Me5 rings being virtually parallel. The compound is paramagnetic. Crystals of 2 consist of parallel rows of cations and tcne˙- anions in the sequence · · · D˙ AA˙-D˙+A B˙-D˙+AA ˙-D˙+AB˙ - · · ·, where AA˙- and AB˙- label crystallographically independent anions. The two types of tcne˙- anion are themselves approximately planar, but define different angles to the planes of the adjacent C5Me5 rings of 4 and 72°. Magnetic susceptibility measurements for 2, in the range 5.0 to 310.0 K, suggest very little magnetic coupling between the unpaired spins on the cations and the tcne˙- anions and thus this compound is also paramagnetic.

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