A DYNAMIC NMR-STUDY OF 1,2-METALLOTROPIC SHIFTS IN TRIMETHYLPLATINUM(IV) HALIDE-COMPLEXES OF 3-METHYLPYRIDAZINE

3-Methylpyridazine (3-Mepydz) reacts with halogenotrimethylplatinum(IV), [(PtXMe(3))(4)], to afford complexes of type fac-[PtXMe(3)(3-Mepydz)(2)] (X = Cl, Br or I). In solution these complexes undergo 1,2-metallotropic shifts between the contiguous nitrogen donors producing different linkage isomers. Solution abundances of these isomers are strongly influenced by the steric effects of the 3-methyl group on the pyridazine ring, with the (1,1)-isomer always being predominant (similar to 95%). Activation energies for the fluxion were determined by variable temperature H-1 NMR spectroscopy, values of the (1,1) --> (1,2) isomer shift being in the range 74-78 kJ mol(-1).