Vanadium complexes azide

Another interesting point is the relative rates of the reactions of the azido and thiocyanatopentaammines. The relative rates of these two reactants with iron (I I) ion are similar to those with chromium (I I), that is, the azide is four to five powers of ten more rapid than is the thiocyanato. I am suggesting that this might be a criterion for inner sphere activated complex as opposed to an outer sphere complex. With trisdipyridylchromium(II) ion, which must react via an outer sphere process, the azido and thiocyanato rates are relatively comparable, and the same also for vanadium (I I) ion which also probably procedes via an outer sphere activated complex. 

Parent and derivatized vanadium(V)-tacn complexes (tacn= 1,4,7-triazacyclononane) have been prepared and structurally characterized.435 Various auxiliary ligands have been used including acetylacetonate (acac), isothiocyanate ( NCS), azide, and benzoic acid.436 The acac derivative was used in the synthesis of a nitridovanadium(V) complex (80).436... 

In both cases, the cobalt containing product is the aqua complex because H2O is present in abundance, and high-spin d complexes of Co(II) are substitution labile. However, something that distinguishes the two pathways is the composition of the vanadium-containing product. If [V(N3)(OH2)s] is the product, then the reaction has proceeded via an inner-sphere pathway. If [V(OH2)6] " is the product, then the electron-transfer reaction is outer-sphere. The complex [V(N3)(OH2)5] is inert enough to be experimentally observed before the water molecule displaces the azide anion to give [V(OH2)6]. ... 

Several mixed and hetero azides of vanadium(V) as well as azido complexes of vanadium(II) and (V) have been described. The crystalline vanadyl azide trichloride, VO(N3)Cl3, is made from VOCI3 and chlorine azide as described under the titanium azide. The moisture-sensitive compound deflagrates on thermal shock it is soluble in VOCI3. The brown, solid vanadium azide tetrachloride, V(N3)Cl4, was made accordingly from solid VCI4 and chlorine azide in CCI4 media. In the dry state at room temperature it is stable for several days, but decomposes with water and, less rapidly, with organic solvents. The compound is very sensitive to friction and impact and also explodes on thermal shock [141]. 

Vanadium(III) complexes, 473 adenine, 475 alcohols, 478 amides, 474, 480 amines, 474 amino acids, 484 ammonia, 474 aqua, 477 arsines, 476 azide, 475 bipyridyl, 475 bromides, 483 carboxylates, 479 catecholates, 478 chlorides, 482 complexones, 485 cyanides, 474,476 (Wethyl sulfoxide, 480 dioxygen, 478 dithiocarbamates, 481 dithiolates, 481 dithiophosphinates, 481 ethers, 478... 

It is likely that the reduction of organic azides with vanadium(II) chloride involves the formation of vanadium coordinated nitrene intermediates (65). A nitrene coordinated-Ru(II) ion (65 a) produced by treatment of Ru(III) azide complexes with acid has been identified. 

Parallel to the work of Bergman et al., Cummins et al. published a closely related system obtained from a vanadium(in) precursor and mesityl azide leading to a vanadium(V) diazenylimido complex, which loses dinitrogen already at room temperature. Interestingly, the loss of dinitrogen from the vanadium(V)diazenylimido complex follows second-order kinetics and crossover was found in a double labelling experiment, which is in contrast to the observations of Bergman et al. with tantalum complexes. 

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