NMR STUDIES OF FLUXIONAL RHENIUM CARBONYLCOMPLEXES OF 2,6-DIACETYLPYRIDINE (DAP),fac-[ReX ( CO )a(D AP)]

2,6-Diacetylpyridine (DAP) reacted with pentacarbonylhalogeno rhenium(l)complexes under mild conditions to form stable octahedral complexes of the type fac-[ReX(CO)3(DAP)] (X = CI, Br or I) in which the DAP acts as a bidentate chelate ligand.In solution these complexes are fluxional with DAP oscillating between equivalent bidentatebonding modes by a twist mechanism involving the breaking/making of two Re--O bonds.Rates and activation energies of these fluxions have been investigated by NMR methods. 2-Acetylpyridine (AP) reacts with bromopentacarbonylrhenium(I) to form the non-fluxionalchelate complex fac-[ReBr(CO)3(AP)].