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063ChemInform Abstract Intramolecular mechanisms for the haptotropic shifts of transition-metal centers in monocoordinate complexes with potentially bidentate diimines and azines such as (I)-(VI), e.g., and metals such as Au, Cu, Pt, Ni, Pd, Hg, Cr, Mn, Fe, W, Co, are analyzed by means of qualitative MO studies, and the factors controlling the height of the barriers for such shifts are discussed. Related processes are the tautomerism in protonated formamidinates or triazenides, as well as the haptotropic shifts in main group metal complexes. A common feature for all these systems is the loss of overlap between the acceptor orbital and the diimine's lone pairs along the reaction path, while the unique feature of the transition-metal complexes is the appearance of a four-electron repulsion between the lone pairs and one of the metal's "t2g" orbitals.

ChemInform Abstract The octahedral fac-complexes (III) with monodentately coordinated 1,8-naphthyridine (II) are obtained according to the scheme. Their structure is established by X-ray analysis of the o-phenanthroline complex (IIIa) (space group P21/a, Z=4). A detailed variable-temp. 1H NMR study show that at higher temp. these complexes are fluxional species in which a rapid metal exchange between the two N atoms of naphthyridine takes place.