Zirconium complexes coordination geometries

A related zirconium complex with a [N2 ]-type of ligation is tetrakis(l,3-diphenyltriazenido)zirconium(lv) 74,85 which is obtained from the amine elimination approach. Thus, treatment of Zr(NMe2)4 with 4equiv. of 1,3-diphenyltriazene in hexanes at ambient temperature affords 74 in 79% yield as a deep red crystalline solid (Equation (6)). This Zr complex is eight coordinate with four 2-l,3-diphenyltriazenido ligands. Complex 74 crystallizes with a distorted dodecahedral geometry about Zr consistent with this solid-state structure, the solution molecular weight measurements indicate a monomeric structure in benzene. 

The X-ray crystal structure of the tris( n4-naphthalene)zirconate(2-) anion as the bis[K(2,2,2-crypt)] salt has been determined, revealing a trigonal prismatic coordination geometry of local Csv symmetry about the zirconium atom, as defined by the mid-points of the C-C vectors of the coordinated diene units, similar to that eviously observed for the isoelectronic tris(ii i-butadiene)molybdenum complex. 

Biihl M, Hopp G, von Philipsborn W, Beck S, Prosenc M-H, Rief U and Brintzinger H-H (1996) Zirconium-91 chemical shifts and line widths as indicators of coordination geometry distortions in zirconocene complexes. Organometallics 15 778-785. 

Coordination numbers (CN) of zirconium and hafnium range from 4 to 12, but because of the large values of their ionic and covalent radii (see Covalent Radii) (Table 1), their complexes typically have CNs of 6-8 (see Coordination Numbers Geometries). They have a varied stereochemistry... 

Analytical Chemistry of the Transition Elements Coordination Numbers Geometries Coordination Organometallic Chemistry Principles Hydride Complexes of the Transition Metals Oxide Catalysts in Sohd-state Chemistry Periodic Table Trends in the Properties of the Elements Sol Gel Synthesis of Solids Structure Property Maps for Inorganic Solids Titanium Inorganic Coordination Chemistry Zirconium Hafnium Organometallic Chemistry. 

Zirconium is the principal FP to arise in oxidation state (IV). Where Zircaloy clad fuel is involved, nonradioactive zirconium isotopes may also be present from fuel can residues. As with ruthenium, there may be a variety of nitrato complexes present in the solution including the aquated complexes Zr(N03)s where x = 1-6, and hydroxy nitrato complexes. However, species containing ZrO " " are not expected to be present since this ion is unstable in aqueous media and is rapidly hydrated to Zr(OH)2. The extraction chemistry is further complicated by the formation of inextractable polymeric species when the Zr" concentration exceeds ca. 10 M. An example of such oligomerization is afforded by the [Zr(0H)2(H20)4]4 ion which contains four Zr ions in a square arrangement linked by two /u-OH ligands on each square edge. Four water molecules complete the Zr coordination sphere in an approximately D2d dodecahedral geometry. 

Treatment of a benzene solution of the sterically crowded bis(aryloxide)zirconium dibenzyl complex 5 with BIC F5)3 leads to the facile formation of the corresponding zwitterionic species 6 (Scheme 3).44 The molecular structure of 6 features a three-legged piano-stool geometry about Zr with the 7/ -bound benzyl group and the tightly associated benzyl borate anion through r/ -arcne coordination this complex is stable in solution in the presence of propylene and phenylpropyne. In contrast, treatment of the 2,6-di-Buc-substituted aryloxide dibenzyl derivative 7 with B(C6Fs)3 forms the cyclometallated compound 8 after elimination of toluene (Scheme 3) 45 compound 8 was structurally characterized. 

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