Acta Chim. Slov. 44 (1997) 131-141.

STRUCTURAL STUDIES OF THE HALOPYRIDINE COMPLEXES OF TRIVALENT ELEMENTS

J. V. Brencic

Faculty for Chemistry and Chemical Technology, University of Ljubljana,
Askerceva 5, P.O.Box 537, 1001 Ljubljana, SLOVENIA

Halopyridine complexes of trivalent elements are known for about 100 years, but the first two crystal structures, namely W₂Cl₆py₄ and trans-TiCl₃py₃.py (py=pyridine, C₅H₅N) were published yet in the years 1971 and 1972. The majority of monomeric halopyridine complexes of the trivalent metals have octahedral coordination described by formula [MX_npy_6-n]^3-n (n=1-5). Five different stoichiometries make possible eight structural types. Out of eight possibilities five have known crystal structures: [MX₅py]^2-, trans and cis-[MX₄py₂]^–, mer-[MX₃py₃] and trans-[MX₂py₄]⁺. From the nonoctahedral complexes only TlBr₃py₂ with distorted trigonal-bipyramidal structure is known. Three of dimeric M₂X₆py₄ complexes were also characterised by crystal structure analysis.