Li_xB - A LITHIUMBORIDE CONTAINING LINEAR BORON CHAINS. Michael Wörle, Reinhard Nesper, Laboratorium für anorganische Chemie, ETH Zürich, Universitätsstr. 6, CH-8092 Zürich.

The structure, magnetic and spectroscopic properties of Li_xB (0.67<x<1.22) are reported. The composition of this compound has earlier been described as Li₅B₄ [1] or Li₇B₆ [2,3]. Hitherto published structural data are wrong.

The compound crystallizes in the space group P6₃/mmc. The lattice constants are with a = 402.86 pm and c = 290.2 pm (for x=1) or a = 401.81 pm and c = 279.4 pm (for x=1.22) dependent on the lithium content. The crystal structure was determined from X-ray powder diffraction data.

The structure consists of a distorted hexagonal closed packing of lithium atoms. The stacks of octahedra are centered by linear chains of boron atoms along the crystallographic c-axis.

This is the first compound known to contain isolated linear [B]^--chains in the ideal case. However, crystal defects limit the average chain length to about 67 boron atoms and lead to variations of the stoichiometry. These chains are the first examples of carbinoid systems (boryne) of a really large size.

[1] F. E. Wang, M. A. Mitchell, R. A. Sutula; J. Less Common Met., 57,(1978), 161

[2] R. Szwark, R. D. Walton, S. Dallek, B. F. Larrick; J. Electrochem. Soc. 129,

(1982),1168

[3] D. W. Ernst; J. Electrochem. Soc., 129, (1982), 1513