Chemistry Reference
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Fig. 10
One-dimensional halogen bonded system involving
E
-TTFI
2
and the octahedral
polycyano cluster anion [Re
6
Se
6
(CN)
6
]
4-
the other involving the oxygen atom of a carbonyl (Fig. 10). This work was
further extended by the same authors to thiocyanate anions such as the
S
=3
2 [Cr(isoq)
2
(NCS)
4
]
-
ion where, upon association with EDT-TTF-I
2
or
EDT-TSF-I
2
,C- I
/
···
SCN - interactions can now be identified [79].
3.3.2.2
Organic Nitrile-Containing Anions
The most popular organic nitrile-containing anions used so far in their salts
with halogenated TTFs are the square-planar metal dithiolene complexes of
the mnt dithiolate, formulated as [M(mnt)
2
]
-
,M=Ni,Pt,Pd(Scheme9).
Dithiolene complexes have been extensively used for the elaboration of con-
ducting [80] or magnetic materials [81-83]. The non-innocent character of the
dithiolate ligand allows for multiple redox states, some of them paramagnetic.
Let us mention the [M(mnt)
2
] complexes,knownintheirdianionic(
S
=0)or
monoanionic (
S
=1
2) states, or the [M(dmit)
2
] complexes, known as dianion,
monoanion or mixed-valence, formally - 0.5 ions in conducting systems. The
presence of nitrile substituents combined with their negative charge make the
[M(mnt)
2
] complexes ideal counter ions to favour halogen bond interactions
with halogenated TTFs. There are, however, only five reported examples of such
salts, which are collected in Table 4 with their structural characteristics. Note
the short and strongly linear C - I
/
···
N
≡
Cinteractioninallofthem.
Scheme 9
Metal dithiolene complexes
In (TTF - I)
2
[Pd(mnt)
2
], dyads of fully oxidized (TTF-I)
+
·
radical cations
alternate with the dianionic [Pd(mnt)
2
]
2-
affording an insulating salt [84].
On the other hand, the EDO-TTF-I
2
salts of [Ni(mnt)
2
]
-
and [Pt(mnt)
2
]
-
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