Niobium stereochemistry

Table 22.2 Oxidation states and stereochemistries of compounds of vanadium, niobium and tantalum...

Niobium, tetrakis(2,2,6,6-tetramethyl-3,5-heptanedione)-stereochemistry, 1, 94 structure, 1, 93... 

Niobium, tris(diethyldilhiocarbamato)oxy-stereochemistry, 1,82 structure, 1, 83 Niobium, tris(oxa ato)oxy-stereochcmistry, 1, 82 Niobium, tris(phcnylcncdirhio)-structure, 1, 63 Niobium alanate, 3, 685 Niobium complexes alkyl alkoxy reactions, 2, 358 amides, 2,164 properties, 2, 168 synthesis, 2, 165 applications, 6,1014 carbamicacid, 2, 450 clusters, 3, 672,673,675 hexamethylbenzene ligands, 3, 669 cyanides synthesis, 2, 9 p-dinitrogen, 3, 418 fluoro... 

Table 18-B-l Oxidation States and Stereochemistries of Niobium and Tantalum...

Niobium and tantalum, though metallic in many respects, have chemistries in the V oxidation state that are very similar to those of typical non-metals. They have virtually no cationic chemistry but form numerous anionic species. Their halides and oxide halides, which are their most important simple compounds, are mostly volatile and are readily hydrolyzed. In their lower oxidation states they form an extraordinarily large number of metal-atom cluster compounds. Only niobium forms lower states in aqueous solution. The oxidation states and stereochemistries (excluding those in the cluster compounds) are summarized in Table 26-B-l. 

The stereochemistry of tetrakis (dipivaloylmethanato)niobium(iv) has been shown by X-ray analysis to be the first example of a M(bidentate)4 complex whose stereochemistry is based on an idealized square antiprism (38)." The first Ta pure n.q.r. spectra have been detected in Ta2X o (X = Q or Br) as part of a detailed n.q.r. study of such dimers. ... 

Tetrakis(dipivaloylmethanato)niobium(iv), [Nb (Bu CO)2CH 4] has been prepared by treating NbCl4 with dipivaloylmethane in MeCN containing EtjN. X-Ray crystallographic studies have shown that this compound is the first example of an M(bidentate)4 complex whose stereochemistry is based on an idealized D4 square antiprism (38). In the absence of oxygen and moisture, [Nb (Bu CO)2CH 4] affords stable, very weakly conducting solutions in CH2CI2 which contain the monomer. ... 

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