Metals tetrachloride

At 1400°C and reduced pressure, ZrB2 and HfB2 codeposit with considerable amounts of -rh boron owing to the low vapor pressure of Zr and Hf tetrachlorides. Excess hydrogen and metal tetrachloride are necessary to minimize the formation of uncombined boron. ... 

The preparation of Th, U and Np tetracyclopentadienides were accomplished by the straightforward reaction of the anhydrous metal tetrachloride with potassium cyclopentadienide in benzene (6). Tetrakis(cyclopentadienyl) pro-tactinium(IV) was prepared using Be(CsH5)2 and Pads prepared in situ (6). Infrared data suggest that aU of the tetracyclopentadienides possess similar molecular structures the Th, U and Np complexes were found to be isostmctural by powder techniques (79, 80). 

Tan colored K2[M(NCSe)6] (M = Zr or Hf) complexes have been prepared by extracting the metal tetrachlorides into an acetonitrile solution of KSeCN. IR spectra indicate an N-bonded attachment of the NCSe ligands.106... 

Compounds of composition [CsH5NH]2[MCl4(OMe)2] (M = Zr or Hf), [C5H5NH]2-[ZrCl5(OEt)] and [CsHsNH]2[ZrCl2(OEt)4] have been prepared by reaction of the metal tetrachlorides with methanol or ethanol in the presence of pyridine.214... 

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... 

Compounds of the type M(NR2)4 (M = Th or U) are obtained by reaction of the metal tetrachloride with LiNR2 in non-aqueous solvents. They are all highly reactive towards protonated species and they readily undergo C02, COS, CS2 or CSe2 insertion into the M—N bond to form carbamates. 

In the thiocyanate case, the complexes of the metal tetrachlorides are simply treated with the stoichiometric quantity of KNCS in suitable solvents. In some instances the preparations can be carried out in one step from the metal tetrachloride, potassium thiocyanate and the ligand, but this procedure can make the purification of the final product quite difficult. A number of complexes of the type (i -QHsJMXaL (M = Th,U,Np) have been recorded these are described elsewhere.187... 

Tetrakis(allyl) complexes of thorium and uranium have been synthesized via the addition of allyl Grignard to the metal tetrachloride (equation 43). Alkyl-substituted allyl... 

Summary Oligosilanes with trimethylsilyl groups react with one or two molar equivalents of potassium rcrr-butoxide in the presence of tetramethylethylenediamine (tmen) to yield quantitatively oligosilyl mono- and dianions (1, 2). Conversion of these compounds with Group 4 metal tetrachlorides leads to a novel type of Cp-free oligosilyl Group 4 metal chloride tmen complexes. 

The compounds of general composition M(NR2)4, where M is zirconium and R is methyl, ethyl, w-propyl, or i-butyl were prepared either by treating the metal tetrachloride with the appropriate lithium dialkyl-amide or bjr ammonolysis of a tetrakisdialkylaminometal compound with another dialkylamine (75). The latter method may give dialkyl-amino derivatives of the type M(NR2)a (NR )4 j , where R is ethyl,... 

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