SYNTHESES AND CRYSTAL-STRUCTURES OF SALTS OF HEXABROMOTETRASELENATE(I) AND HEXABROMOSELENATE(IV)BIS(DIBROMODISELENATE(I))

The title compounds have been prepared from elemental selenium and bro mine, and phenyltrimethylammonium bromide or benzyltrimethylammonium b romide. The crystal structures of [C6H5(CH3),N](2)[Se4Br6] (1), [C6H5C H2(CH3)(3)N](2)[Se4Br6] (2) and [C6H5(CH3)(3)N](2)[SeBr6(Se2Br6)(2)] ( 3) were determined by X-ray methods. Crystals of 1 and 2 are monoclini c, space group P2(1)/c (No. 14) with Z=2 and a= 8.618(2), b=12.914(2), c=13.609(3) Angstrom and beta=95.13(2)degrees for 1, and a=8.417(2), b=12.673(3), c=14.813(3)Angstrom and beta=for 97.06(3)degrees for 2. T he crystals of 3 are monoclinic, space group P2(1)/n (No. 14) with Z=2 and a=8.683(2), b=12.762(3), c=16.340(3) Angstrom, beta= 104.29(3)deg rees The anions of 1 and 2 consist of two Br-Se Se-Br units bonded tog ether by two Br atom bridges between the Se atoms in such a way that a chair-shaped, six-membered ring is formed and the Se-Br bends of the Br-Se-Se-Br units are pointing out of the ring. The anion of 3 is a ne arly regular SeBr6 octahedron where two trans-positioned Br atoms each have a weak bond to one of the Se atoms in a Se(2)Br(2)molecule.