HETEROATOMIC POLYANIONS OF POST TRANSITION-ELEMENTS - SYNTHESIS AND STRUCTURE OF A SALT CONTAINING THE NOVEL TETRA ANTIMONY HEXASELENATE(2-) ANION [SB4SE6](2-)

The salt [P(Ph)(4)](2)[Sb4Se6] was obtained by electrochemical reducti on of the Sb2As2Se4 alloy in ethylenediamine-tetraphenylphosphonium br omide electrolyte. The crystal is triclinic, space group P ($) over ba r 1, a = 10.125(2), b = 14.638(5), c = 17.337(4) Angstrom, alpha = 96. 47(2), beta = 95.67(2), gamma = 96.99(2)degrees, Z = 2. The structure was solved by direct methods and refined by full matrix least-squares to a final R (F) of 0.059 (Rw (F) = 0.075). [Sb4Se6](2-) displays a '' cradle'' structure different of the inverted geometry observed for the homologues [As4Se6](2-) and [As4Te6](2-).