Diethyl ether hafnium

Zirconium(IV) and hafnium(IV) tetrakis(tetrahydroborates) M(BH4)4 are of interest as extremely volatile, covalent complexes that contain tridentate BH ligands and exhibit rapid intramolecular exchange of bridging and terminal hydrogen atoms. 4,615 These compounds were prepared initially from NaMF5 (M = Zr or Hf) and excess A1(BH4)3 (equation 53),616 but they are obtained more conveniently from the reaction of the anhydrous metal tetrachloride with excess lithium tetrahydroborate (equation 54), either in the solid state617,618 or in the presence of a small amount of diethyl ether.619... 

The selective extraction of hafnium from thiocyanate media into diethyl ether was first reported in 1947.300.30i xhe technique was subsequently investigated extensively in the USA with a view to the development of a suitable industrial-scale process, it being found advantageous for MIBK to be used as the solvent in place of diethyl ether.302 The first commercial plant was completed in 1952,303 ancj the process has since been used widely in the USA, England, France, Germany and Japan. Several descriptions of the process have been given in the literature.287-289 303-305... 

Bercaw and co-workers showed that pentamethylcyclopentadienyl-aminoborole complexes of hafnium and zirconium 52 react with allyl magnesium bromide in diethyl ether to yield the allyl complexes 53 (Equation 8) <1997JOM65>. 

In contrast to this, reduction of P3C3Bu 3 with 3 equiv of GaH3(quin) (quin = quinuclidine) in diethyl ether cleanly gave the triphosphabicyclo[3.1.0]hexane complex 35 in low yield. Acid quenching followed by basic workup led to the free bicyclic diphosphirane 28a which is an isomer of the bicyclic diphosphirane 28 previously liberated from a hafnium complex <1999EJI763>. 

History. In 1947, Fischer and co-workers [FI, F2] described a solvent extraction method for separating hafnium from zirconium in which an aqueous solution of sulfates containing ammonium thiocyanate was extracted with diethyl ether containing thiocyanic acid. Hafnium concentrates preferentially in the organic phase in one reported experiment zirconium in the aqueous phase contained 0 percent hafnium, while the organic phase zirconium contained more tlum 5 percent. Six to eight batch laboratory separations concentrated hafnium from 0.5 percent in zirconium to 70 to 90 percent. 

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