R. Pottgen et al., THE BINARY SILICIDES EU5SI3 AND YB3SI5 - SYNTHESIS, CRYSTAL-STRUCTURE, AND CHEMICAL BONDING, Zeitschrift fur anorganische und allgemeine Chemie, 624(6), 1998, pp. 945-951
Citations number
36
Categorie Soggetti
Chemistry Inorganic & Nuclear
Journal title
Zeitschrift fur anorganische und allgemeine Chemie
The binary silicides Eu5Si3 and Yb3Si5 were prepared from the elements
in sealed tantalum tubes and their crystal structures were determined
from single crystal X-ray data: I4/mcm, a = 791.88(7)pm, c = 1532.2(2
)pm, Z = 4, wR2 = 0.0545, 600 F-2 values, 16 variables for EU5Si3 (Cr5
B3-type ) and P (6) over bar 2m, a = 650.8(2)pm, c = 409.2(1)pm, Z = 1
, wR2 = 0.0427, 375 F-2 values, 12 variables for Yb3Si5 (Th3Pd5 type).
The new silicide Eu5Si3 contains isolated silicon atoms and silicon p
airs with a Si-Si distance of 242.4 pm. This silicide may be described
as a Zintl phase with the formula [5EU(2+)](10+)[Si](4-)[Si-2](6-). T
he silicon atoms in Yb3Si5 form a two-dimensional planar network with
two-connected and three-connected silicon atoms. According to the Zint
l-Klemm concept the formula of homogeneous mixed-valent Yb3Si5 may to
a first approximation be written as [3Yb](8+)[2Si(-)](2-)[3Si(2-)](6-)
. Magnetic susceptibility investigations of Eu5Si3 show Curie-Weiss be
haviour above 100K with a magnetic moment of 7.85(5) mu(B) which is cl
ose to the free ion value of 7.94 mu(B) for EU2+. Chemical bonding in
Eu5Si3 and Yb3Si5 was investigated by semi-empirical band structure ca
lculations using an extended Huckel hamiltonian. The strongest bonding
interactions are found for the Si-Si contacts followed by Eu-Si and Y
b-Si, respectively. The main bonding characteristics in EU5Si3 are ant
ibonding Si1(2)-pi and bonding Eu-Si1 states at the Fermi level. The
same holds true for the silicon polyanion in Yb3Si5.