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Abstract:
Purple air-stable crystals of Ir8Se40Br10 were obtained by reacting Ir
in an excess of Se and SeBr4 at 300 degrees C for two weeks. The
monoclinic crystal structure [space group P2(1)/c, a = 1371.9(1) pm, b =
1108.1(1) pm, c = 2058.2(1) pm, beta = 106.897(2)degrees at 296(1) K]
consists of uncharged clusters Ir8Se40Br10 =
(Ir3+)(8)(Se-2(2-))(Se-4(2-))(6)(Se-7)(2)(Br-)(10). The iridium(III)
cations are coordinated octahedrally by selenium and bromide ions. While
the oligoselenide anions provide high intra-cluster connectivity,
mu(6)-eta(2) in the case of Se-2(2-) and mu(4)-eta(3) for Se-4(2-), the
terminal uncharged Se-7 rings have boat conformation and are
eta(1)-coordinating. About 10% of the Se-7 rings are substituted by Se-6
rings with chair conformation. A similar reaction using SeCl4 yielded
vermillion air-stable crystals of Ir2Se9Cl6. X-ray diffraction on a
single-crystal revealed a tetragonal lattice (space group I4(1)/a) with
a = 1229.8(1) pm and c = 2365.5(2) pm at 296(1) K. In the Se-9(IrCl3)(2)
cluster, a crown-shaped uncharged Se-9 ring coordinates two iridium(III)
cations as a bridging bis-tridentate ligand. Three terminal chloride
ions complete the distorted octahedral coordination of each transition
metal atom.
