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Abstract:
The reaction of selenium and NbCl5 with arsenic in the Lewis-acidic
ionic liquid BMImCl center dot 4.8AlCl(3) at 100 degrees C yielded
dark-red block-shaped crystals of Nb2Se4(AlCl4)(4), which immediately
decompose when exposed to humid air. Arsenic takes the part of the
reducing agent for niobium as well as selenium. The crystal structure
was described in the monoclinic space group P2(1)/n (no. 14) with a =
898.0(1) pm, b = 991.3(1) pm, c = 1629.1(2) pm, and beta =
92.43(1)degrees at 296(1) K. The unit cell contains two C-2h symmetric
Nb-2(Se-2)(2)(AlCl4)(4) molecules. The latter consist of a central
rectangular bipyramid [Nb-2(Se-2)(2)](4+) and four eta(2)-coordinating
AlCl4- tetrahedra. Diamagentism of the compound and DFT-based real-space
bonding analysis imply a chemical bond between the niobium(IV) cations,
which are 292.2(2) pm apart. Nb2Se4(AlCl4)(4) can be interpreted as the
AlCl3 adduct of NbSe2Cl2.
