STRUCTURE OF TETRAMETHYLAMMONIUM TETRABROMOCOBALTATE AT ROOM-TEMPERATURE

The structure of tetramethylammonium tetrabromocobaltate, [N(CH3)(4)]2 CoBr4, has been determined at room temperature by single-crystal X-ray diffraction. The thermal parameters of the Br and C atoms are unusual ly large and highly anisotropic. The electron-density contour map and Hamilton significance test indicate that two non-equivalent kinds of N (CH3)(4) molecule and one kind of CoBr4 molecule are all disordered sy mmetrically with respect to mirror planes. The CoBr4 tetrahedron is al most undistorted, while the distortions of the N(CH3)(4) tetrahedra ar e large.