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Abstract:
The reaction of antimony and selenium in the Lewis-acidic ionic liquid
1-butyl-3-methyl-imidazolium tetrachloridoaluminate, [BMIm]Cl center dot
4.7AlCl(3), yielded dark-red crystals of [Sb2Se2]AlCl4. The formation
starts above 160 degrees C; at about 190 degrees C, irreversible
decomposition takes place. The compound crystallizes in the triclinic
space group P (1) over bar with a = 919.39(2) pm, b = 1137.92(3) pm, c =
1152.30(3) pm, alpha = 68.047(1)degrees, beta = 78.115(1)degrees, gamma
= 72.530(1)degrees, and Z = 4. The structure is similar to that of
[Sb2Te2] AlCl4 but has only half the number of crystallographically
independent atoms. Polycationic chains (1)(infinity)[Sb2Se2](+) form a
pseudo-hexagonal arrangement along [01 (1) over bar], which is
interlaced by tetrahedral AlCl(4)(-)groups. The catena-heteropolycation
(1)(infinity)[Sb2Se2](+) is a sequence of three different four-membered
[Sb2Se2] rings. The chemical bonding scheme, established from the
topological analysis of the real-space bonding indicator ELI-D, includes
significantly polar covalent bonding in four-member rings
withinthepolycation.
Theringsareconnectedintoaninfinitechainbyhomonuclear non-polar Sb-Sb
bonds and highly polar Sb-Se bonds. Half of the selenium atoms are
three-bonded.
