NbCls

A very active, high yields but extensive intra- and intermolecular isomerisation AlCl, AlBr, A1L, GaCl, GaCl2, GaBr, Gal, ZrCl, HfCl, HfBr, Hfl, SbF, NbF, NbCl, TaF, TaCl, TaBr, MoF, and MoCl ... 

The reaction temperature of 500—600°C is much lower than that required for the reductive chlorination. The volatile chlorides evolve from the molten salt bath. The boiling points of NbCl, TaCl, and WOCl He between 228 and 248°C. These compounds must therefore be separated by means of a distillation column. The chlorination of ferroalloys produces very pure tantalum pentachloride in toimage quantities. The TaCl contains less than 5 )J.g Nb/g Ta, and other metallic impurities are only amount to 1—2 lg/g Ta. 

A related example is the reaction of NbCls and thf with (Me3Si)2NN(SiMe3)2 in CH2CI2 to give an 80% yield of [(/Lt-N2) NbCl3(th02 2]- Occasionally an N=N triple bond can be formed within a metal complex, e.g. by reaction of coordinated NH3 with HNO2, but this method is of limited application, e.g. ... 

NbFjl ) blue NbCL black NbBr3 dark brown NbL... 

NbCls (pyrazolyl)3BFI ], 3,622 NbBr30 NbOBr3,3. 626 NbBr4... 

Metathetical reactions between NbCl4(THF)2, NbCls, TaCls, [(Et2N)2TaCl3]2, or (R2N)3Ta(=NBu (R = Me, Et) with various amounts of lithium amidinates have been employed to synthesize the corresponding heteroleptic niobium and tantalum amidinate complexes. The products were investigated as potential precursors to metal nitrides (cf. Section VI) Carbodiimide insertion routes... 

Scheme 1. Summary of reactions between NbCls, NbBrj, and TaBrj and Nadtc, B = benzene, MC = dichloromethane all NbX,/Nadtc B reactions also produce NbdtC4 (not shown), all MXj/Nadtc/MC reactions also produce dtcjCH (not shown).

Generally, it is not important in which form the components are introduced into the transport tube, because the transport reaction transfers the whole system into a reversible state. In the preparation of NbS2Cl2, for example, Nb and S2C12, as well as Nb, S, and NbCls, have been used as starting materials (339). The principles of chemical transport reactions are treated in refs. 241, 336, 337, 338). 

Dirheniumheptoxide 2154 is converted by TCS 14, in the presence of 2,2 -dipyri-dine, into the dipyridine complex 2160 [77]. Free ReCls, NbCls, and WCI5 react with HMDSO 7 and 2,2 -bipyridine to form bipyridine oxochloride complexes 2161 and TCS 14, with reversal of the hitherto described reactions of metal oxides with TCS 14. The analogous Mo complex 2162 undergoes silylahon-amination by N-trimethylsilyl-tert-butylamine 2163 to give the bis-imine complex 2164 and HMDSO 7 [77] (Scheme 13.22). 

Nb 0.3 THFfi NbCL 2THF K[BEt3H] Room temperature 4 48 -... 

Sn/V/Nb/Sb/0 catalysts were prepared with the co-precipitahon technique, developed for the synthesis of ratile Sn02-based systems claimed by Rhodia (8). The preparation involved the dissoluhon of SnCl45H20, VO(acac)2, SbCh and NbCls in absolute ethanol, and by dropping the soluhon into a buffered aqueous soluhon maintained at pH 7. The precipitate obtained was separated from the liquid by filtrahon. The solid was then dried at 120°C and calcined in air at 700°C for 3 hours. The V/Sb/0 catalyst was prepared by means of the slurry method that consists in a redox reachon between Sb203 and NH4VO3 in water medium, for 18h at 95°C. The... 

The relatively low reactivity of diorganozinc compounds is demonstrated by the fact that even the addition of 2 or 3equiv. of ZnPh2 to [NbCl2 N(SiMe3)2 2] gave only the monophenyl product [NbCl N(SiMe3)2 2Ph].61... 

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