Crystal Structures and Properties of MMX-Chain Compounds Based on Dithiocarboxylato-Bridged Dinuclear Complexes - Material Designs and New Physical Properties in MX-and MMX-Chain Compounds - page 183

Fig. 9.32 1D chain structures of (a) [Ni 2 ( n -PrCS 2 ) 4 I] 1 (9) in the RT phase at 240 K and
(b) [Ni 2 ( n -BuCS 2 ) 4 I] 1 (10) at 290 K with an atomic numbering scheme and relevant interatomic
distances (thermal ellipsoid set at the 50 % probability level) [ 38 ]

a low-temperature (LT) phase [ 80 ]. In the compound 10, on the other hand, three
relatively sharp anomalies around 260 K were observed, while a broad anomaly was
observed around 135 K [ 81 ] These facts indicate the existence of three phases of
room temperature (RT), middle temperature (MT), and low temperature (LT). The
1D chain structures of 9 for the RT phase at 240 K and 10 at 290 K are shown in
Fig. 9.32 [ 38 ].
The RT phase of 9 at 240 K and 10 at 290 K crystallize in the monoclinic space
group C 2/ m and tetragonal space group P 4/ mnc , respectively. Since the crystal
structures of 9 and 10 are very similar, the RT phase of 9 is described here.
These structures are also analogous to those of the RT phases of the platinum
compounds 3-5. The unit cell dimension b along the 1D chain in 9 consists of three
-Ni-Ni-I- units. Crystallographic mirror planes perpendicular to the 1D chain exist on
the I1 atoms and the midpoint of Ni3 and Ni3 0 atoms. Therefore, the ligand moieties
including sulfur atoms of Ni3-Ni3 0 units are disordered on two positions and the
twisting directions of two NiS 4 planes of adjacent dinuclear Ni1-Ni2 units in the
1D chain are opposite to each other. Two nickel atoms are bridged by four
dithiobutanato ligands and the Ni-Ni distances are Ni1-Ni2

¼ 2.5336 (8) and

2.5502 (11) ˚ ,whichare0.23 ˚ shorter than the distances between
the mean planes defined by the four sulfur atoms (2.763 (3) and 2.781 (3) ˚ ),
respectively. The twist angle between two NiS 4 planes are 28.9 (1) for a
Ni1-Ni2 unit and 27.4 (2) for a Ni3-Ni3 0 unit, respectively. Three Ni-I
distances are Ni1-I1

Ni3-Ni3 0 ¼

2.9374
(6) ˚ . Taking into account the differences in the Ni-I distances, the valence-
ordered state of the nickel atoms in the threefold periodic structure may be regarded
as -I -Ni 3+ -Ni 2+ -I -Ni 2.5+ -Ni 2.5+ -I -Ni 2+ -Ni 3+ -I -. In such a valence state, the

¼ 2.8642(5), Ni2-I2 ¼ 2.9446(6), and Ni3-I2 ¼