Fluxional compounds

AI(BH4)3 was the first fluxional compound to be recognized as such (1955) and its thermal decomposition led to a new compound which was the first to be discovered and structurally characterized by means of nmr ... 

Recently, dithio-diolate ligands have been employed for construction of group 4 metal catalysts for the ROP of lactide. These metal dithiolate complexes form mononuclear species of the type [(OSSO)M(OR)2] with an octahedrally coordinated metal center. These fluxional compounds acted as highly active catalysts in the ROP of L- and rac-lactide. Hafnium complexes were also introduced as initiators for the ROP of L-lactide and rac-lactide (vide infra) in very limited cases. To our knowledge, the hafnium derivative 146 displayed the highest activity among the group 4 catalysts reported to date (complete conversion of 300 equiv. of... 

Besides the M(S2CNMe2)5 compounds just mentioned, many other dithiocarbamates are known, of which the cationic species [M(S2CNR2)4]+ are most important. They generally have dodecahedral structures in which the S2CNR2 ligands span the four m edges (see Fig. 1-4) of the dodecahedron, but many are fluxional. Compounds of this type can be made by the reaction ... 

Metal hydrides were among the earliest fluxional compounds to be studied. The more recent discovery of dihydrogen complexes and stereochemical nonrigidity in complexes containing both hydride and dihydrogen ligands has provided one of the areas of most intense interest in DNMR in recent years. ... 

This fluxional compound is prepared by reducing FeCl2(PMe3)3 with Na-Hg in THF at 0°C in the presence of excess trimethylphosphine. The closely related Ru... 

At higher temperatures, allyl complexes are no longer rigid they become dynamic, fluxional compounds. Therefore, AM2X2 spectra become AX4 spectra. Temperatures of such transitions for various compounds range from 200 to 450 K. The hafnium allyl compound [Hf( / -C3H5)4] exhibits an AX4-type spectrum even at 199 K. For dynamic... 

The Berry mechanism is used for the interconversion of trigonal bipyramidal and square pyramidal forms of Fe(C0)5, a represerrtative fluxional compound. A given ligand may be axial in one of the trigonal bipyramids but equatorial in another. 

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