Barium zincate

In Fig. 4.79 the DTA curves for the pyrosynthesis of barium zincate out of barium carbonate and zinc oxide are shown. The experiment was done by simultaneous DTA and thermogravimetry on 0.1 cm samples in an oxygen atmosphere. Curve A is the heating trace of the mixture of barium carbonate and zinc oxide. The DTA curve is rather complicated because of the BaCOj solid-solid transitions. The loss of COj has already started at 1190 K. The main loss is seen between 1350 and 1500 K. On... 

Other examples of this series include a selection of ate complexes prepared by the treatment of alkylzinc reagents with freshly distilled alkaline earth metals under extrusion of elemental zinc. This route was employed to prepare a strontium zincate in which the alkaline earth metal center adopts a distorted octahedral geometry completed by two THF solvent donors. Similar reactions with barium metal lead to structurally closely related compounds. Flexibility in solvent choice is noted by the preparation of related complexes in toluene, displaying metal-toluene itt-interactions. 

An aqueous precursorfor 0.75Pb(Zni/3- Nb2/3)O3-0.25BaTiOs solid solution was synthesized by Van Werde et al. (2001). They used acetates of lead and zinc, and Nb(V) peroxocitrato complex. The solution of lead zincate niobate was prepared by adding the compounds into aqueous solution of ammonium citrate. The aqueous solution was stable when pH was higher than 8 and the citrate acid/cation mole ratio was higher than 1.5. The aqueous precursor for barium titanate was prepared by using titanium(IV) peroxocitrato complex and barium acetate. They found that the solid solution of PZN and BT is crystallized as a perovskite phase at temperatures as low as 800°C. 

Formation of Zincate Complexes. Zincate compounds such as K(ZnCH2SiMe3)3 are formed in a transmetalation reaction of bis[(trimethylsilyl)methyl]zinc with elemental potassium, or by reaction with potassium salts. Lithium zincates such as Li[Zn(CH2SiMe3)2R] [R = Me, Ph, N(SiMe3)2] can be prepared by reacting the title compound with the corresponding organo-lithium compounds.Transmetalation with alkaline earth metals such as strontium, barium, and calcium affords zincates of the type illustrated in eq... 

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