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)
Abstract
Reaction of the electron-rich thiolate-bridged complex
[Fe
2
(η-C
5
Me
5
)
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
[Fe
2
(η-C
5
Me
5
)
2
(µ-
SEt)
2
(CO)
2
]
2
[tcnq]
2
1 and
[Fe
2
(η-C
5
Me
5
)
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 C
5
Me
5
ligands are cis
disposed with respect to the
Fe · · ·
Fe vector with the dihedral angles between their planes being 71
and 68° for 1 and 2 respectively. The
Fe · · ·
Fe distances are respectively 3.077(2) and 3.069(2) Å.
Crystals of 1 consist of isolated units of composition
D
˙+
(A)
2
2-
D
˙
where D
˙+
denotes the cation and
(A)
2
2-
a
(tcnq)
2
2-
dimer, the planes of the tcnq
moieties comprising the dimer and those of the adjacent
C
5
Me
5
rings being virtually parallel. The compound
is paramagnetic. Crystals of 2 consist of parallel rows of cations and
tcne
˙-
anions in the sequence
· · · D
˙
A
A
˙-
D
˙+
A
B
˙-
D
˙+
A
A
˙-
D
˙+
A
B
˙
-
· · ·,
where A
A
˙-
and
A
B
˙-
label crystallographically
independent anions. The two types of tcne
˙-
anion
are themselves approximately planar, but define different angles to the
planes of the adjacent C
5
Me
5
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.
Fe vector with the dihedral angles between their planes being 71
and 68° for 1 and 2 respectively. The
Fe · · ·
Fe distances are respectively 3.077(2) and 3.069(2) Å.
Crystals of 1 consist of isolated units of composition
D
˙+
(A)
2
2-
D
˙
where D
˙+
denotes the cation and
(A)
2
2-
a
(tcnq)
2
2-
dimer, the planes of the tcnq
moieties comprising the dimer and those of the adjacent
C
5
Me
5
rings being virtually parallel. The compound
is paramagnetic. Crystals of 2 consist of parallel rows of cations and
tcne
˙-
anions in the sequence
· · · D
˙
A
A
˙-
D
˙+
A
B
˙-
D
˙+
A
A
˙-
D
˙+
A
B
˙
-
· · ·,
where A
A
˙-
and
A
B
˙-
label crystallographically
independent anions. The two types of tcne
˙-
anion
are themselves approximately planar, but define different angles to the
planes of the adjacent C
5
Me
5
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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