Niobium complexes chloro

OC, Carbon monoxide (Continued) cobalt, iron, osmium, and ruthenium complexes, 21 58-65 iron complex, 21 66, 68 manganese complexes, 23 34 molybdenum complexes, 23 4-9 niobium complexes, 23 34 palladium complex, 21 49 rhodium complexes, 23 124 ruthenium complex, 21 30 OCH4, Methanol, iridium complexes, 23 127 rhodium complexes, 23 127, 129 OCjHs, Acetone, compd. with carbonyltri-p.-chloro-chlorotctrakis-(triphenylphosphine)diruthcnium (1 2), 21 30... 

The results of solid state reactions of protactinium dioxide and pentoxide with other metal oxides (89, 93-96) support the view that the oxide systems of protactinium resemble those of other actinide elements rather than those of niobium and tantalum. However, when assessing results of this type one must always bear in mind the relative ionic radii of the respective M " and M + ions since they obviously play a large part in determining the structures of the complex phases. This comment applies equally well, of course, to the structural properties of other types of compound and in particular to the high coordination numbers exhibited by protactinium(V) in its chloro and nitrato complexes. 

Other Halides of Niobium(v) and Tantalum(v). All six of these are yellow to brown or purple-red solids best prepared by direct reaction of the metals with excess of the halogen. The halides melt and boil at 200-300° and are soluble in various organic liquids such as ethers, CC14, etc. They are quickly hydrolyzed by water to the hydrous pentoxides and the hydrohalic acid. The chlorides give clear solutions in concentrated hydrochloric acid, forming oxo chloro complexes. 

The synthesis of M(OEt)4 shows that, contrary to previous observations, tetravalent alkoxides are stable in the presence of alcohol, at least for a short time. The alcoholysis of [Nb(NR2)4] usually led to [Nb(OR )s], but oxidation state +IV was retained with bulky alcohols, e.g. for tetra(l-adamanto)niobium and tetra(l adamantylmethoxo)niobium, illustrating the close dependence of the metal s oxidation state on steric requirements. [Nb(l-ado)4] was reported to be monomeric, but the absence of ESR signals down to — 150°C, as well as its reluctance to form complexes (MczNH, PMcs, THT) is puzzling. Dinuclear and tetranuclear diamagnetic niobiiun chlorocatecholates have also been obtained. The Ta alkoxides are limited to some diamagnetic chloro alkoxide adducts. 

CHLORO-COMPLEXES OF PENTAVALENT NIOBIUM, TANTALUM, PROTACTINIUM, TUNGSTEN AND URANIUM,... 

Scheme 5.10 describes the synthesis of niobium alkyl complex [Nb(R-L)Me2l2, 38, obtained from the reaction of niobium chloride complex [Nb(Me-L)Cl2]2, 37, and borate reagent [199]. Compound 37 can be prepared from the reaction of [NbClj] and 2,6-bis(4,6 dimethylsalicyl)-4-ferf-butylphenol [H3(Me-L)] or 2,6-bis(4-methyl-6-tert-butylsalicyl)-4-ferfbutylphenol [HjlBu -L)] in toluene. The Nb-Nb bond distances in these two chloro complexes are 3.554(1) and 3.649(1) A, respectively. 

---