Zirconium complexes pyridine

Bis(arene)zirconium complexes, characteristics, 4, 697 Bis(arylamido)pyridines, with Hf(IV), 4, 792 Bis(aryl) bridges, in complexes with chromium(VI), 5, 346... 

Terminal chalcogenido zirconium complexes (23) are conveniently synthesized by the reactions of dicarbonylzir-conocene with either N2O or the elemental chalcogens (S, Se, Te) see Chalcogens) in the presence of pyridine. The Zr=E bond in these complexes is highly reactive and leads to a variety of 1,2-addition and cycloaddition reactions (Scheme 8). ... 

The coordination chemistry of ancillary amidinate ligands with a pyridine functionality has been described. Magnesium, aluminum, zirconium, and lanthanum complexes have been prepared in which the amidinate anions act as tridentate, six-electron-donor ligands Amidinate ligands containing quinolyl substituents were constructed in the coordination sphere of lanthanide... 

The generation of an unsymmetrical titaniumcyclopentadiene from different acetylenes can then be subjected to a [4+2] cycloaddition with a sulfonylnitrile to form an intermediate complex which collapses under acidic conditions to yield substituted pyridines (Scheme 60 Table 2) <2002JA3518>. A similar reaction using zirconium has been reported <2002JA5059>. 

A variety of new ligand designs and ligand combinations were used in attempts to mimic some properties of the ubiquitous bent metallocene environment at the early metal centers consequently, some of these systems were used in the further development of butadiene zirconium chemistry. The pyridine based chelate zirconium dichloride complex 43 cleanly formed the butadiene complex 44 upon treatment with butadiene-magnesium. Its structure shows that the C4H6 is arranged perpendicular to the chelate ligand plane. Complex 44 inserts one equivalent of an alkene or alkyne to form the metallacyclic 7i-allyl system 4545 (Scheme 13). 

Addition of thiocyanate ions to chloride or perchlorate solntions of zirconium and hafnium yields complexes containing from one to eight isothiocyanate groups per metal atom. These systems are of interest because of the importance of thiocyanate complexes in the extraction and separation of the elements. IR spectroscopy indicates that M-N bonds are present in the violet (Zr) and pink (Hf) complexes [NEt4]2[M(NCS)6] analogous complexes have been obtained with alkali metal cations. In the presence of pyridine, the dodecahedral Zr(bipy)2(NCS)4 complex is produced see Ammonia N-donor Ligands). 

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