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 172

Fig. 9.22 1D chain structure
of [Pt 2 (EtCS 2 ) 4 I] 1 (2)at48K
with an atomic numbering
scheme and relevant
interatomic distances
(thermal ellipsoid set at the
50 % probability level) [ 33 ]

2.675(1) ˚ ), but
there are two different Pt-I bond distances. The short Pt-I distances (Pt2-I2

distances are almost the same (Pt1-Pt2 ¼ 2.673(1) and Pt3-Pt4 ¼

¼ 2.930

2.930(1) ˚ ) are about 0.029 ˚ (1) and Pt3-I2 ¼ less than the long Pt-I distances

2.963(1) ˚ ). The twofold superstructure
originates from the different Pt-I distances since the structures of the two crystallo-
graphic independent [Pt 2 (EtCS 2 ) 4 ] units are almost the same and twisting
between the dinuclear units has not occurred. The observed Pt-Pt and Pt-I
distances indicate that the valence-ordered state in the LT phase is the ACP state
of -Pt 2+ -Pt 3+ -I -Pt 3+ -Pt 2+ -I -, similarly to the structure of 4 in the LT phase [ 33 ].
Kobayashi and Kitagawa have reported from 129 IM¨ssbauer spectroscopy of 2 that
the chain structure and oxidation states of iodine in 2 at 11 K are considered to be as
follows [ 26 , 74 ]:

(Pt1-I1 ¼ 2.954(1) and Pt4-I1* ¼

Pt 2 þ Pt 3 þ I A 0 : 41 Pt 3 þ Pt 2 þ I B 0 : 31

The valence state of Pt expressed as a -[Pt 3+ -Pt 2+ ]- represents a formal oxidation
number. Almost the same results for the M¨ssbauer parameters have also been
observed in 1, indicating the existence of ACP type ground state in the both
compounds [ 26 , 31 , 74 ].

9.2.6.2 [Pt 2 (n-PrCS 2 ) 4 I] 1 (3)

X-ray diffraction photographs of [Pt 2 ( n -PrCS 2 ) 4 I] 1 (3) measured by rotating
around the c axis using synchrotron radiation are shown in Fig. 9.23 [ 34 ].
At 300 K, weak but distinct Bragg spots were observed in the reciprocal positions
indexed as l

1/3 ( c * RT )and l þ 1/2 (3/2 c * RT ), where the l (3 c * RT )is