DYNAMIC BEHAVIOR OF OCTAHEDRAL COMPLEXES OF MANGANESE .1. X-RAY CRYSTAL-STRUCTURE OF FAC-[MN(ETA(1)-1,8-NAPHTHYRIDINE)-ETA(2)-1,8-NAPHTHYRIDINE)(CO)(3)]CLO4-CENTER-DOT-CH2CL2

The addition of 1,8-naphthyridine (naph) to a solution of [Mn(OClO3)(naph)(CO)(3)] at room temperature affords the octahedral complex [Mn(eta(1)-naph)(eta(2)-naph)(CO)(3)]ClO4 (1). This complex can also be obtained when naph is added to a solution of [Mn(OClO3)(CO)(5)]. When naph is reacted with [Mn(OClO3)(CO)(5)] at -80 degrees C and with 1:1 molar ratio, [Mn(eta(1) -naph)(CO)(5)]ClO4 (3) is obtained. This complex changes into (1) at temperatures above 0 degrees C. The crystal structure of[Mn(eta(1)-naph)(eta(2)-naph)(CO)(3)]ClO4 (monoclinic, space group P2(1)/a, a = 16.006(3) Angstrom, b = 12.024(2) Angstrom, c = 13.004(2) Angstrom, beta = 109.85(2)degrees, Z = 4) shows that, the manganese atom displays a slightly distorted octahedral coordination being linked to three facial carbonyl ligands, to two nitrogen atoms of a bidentate 1,8-naphthyridine (eta(2)-naph) and to another nitrogen atom of a monodentate 1,8-naphthyridine (eta(1)-naph). A detailed Variable temperature H-1 NMR study shows this structure persist in solution at low temperature. At higher temperature the complex is fluxional and there is a rapid exchange of the coordination modes of the two naph ligands: the bidentate becomes monodentate and the monodentate bidentate. The mechanism is intramolecular, the rate-limiting step being the opening of the four-membered ring formed by the metal and the eta(2)-naph.