ISSN:
1572-901X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Summary The reactions between niobium and tantalum pentachlorides and tri-t-butylphosphane and tricyclohexylphosphane under various reducing conditions (magnesium turnings, amalgamated magnesium or sodium naphthalenide) were investigated. The products are highly dependent on the experimental conditions. Niobium(IV) adducts: Nb2Cl8[P(Bu-t)3]2 and Nb2Cl8(PCy3)4 were obtained with magnesium turnings, while reduction to Ta2Cl6(PCy3)3 occurred under similar conditions with tantalum. Ligand exchanges from NbCl4(THF)2 also yielded niobium(IV) adducts Nb2Cl8(PR3)3. The formation of the first soluble diamagnetic niobium(IV) adducts appears to be favored by the strong basicity of PCy3 and P(Bu-t)3. However, these crowded niobium(IV) complexes are unstable both in the solid and in solution with respect to niobium(III). Derivatives in oxidation state 3: M2Cl6(PCy3)3 (M=Nb or Ta), Ta2Cl6[P(Bu-t)3]3 and Nb2Cl6[P(Bu-t)3]2 were formed more efficiently with amalgamated magnesium or with sodium naphthalenide. Activation of dinitrogen under mild conditions (normal pressure, room temperature) was observed during the reduction process with magnesium, for both tantalum and niobium; an unstable adduct, Nb2Cl6[P(Bu-t)3]3N2, could be isolated. All products were characterized by elemental analysis, magnetic susceptibility measurements and i.r. spectroscopy; their molecular structure is discussed in terms of the1H and31P n.m.r. data.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00935927
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