Tetrakis hafnium

Stabilized compounds are inherently more stable then those compounds, which contain /1-hydrogens. Therefore, catalysts where the -positions are blocked, are preferred (8). Examples are zirconium tetrakis(trimethylsilylmethyl) or hafnium tetrakis(trimethylsil-ylmethyl). Catalyst supports are porous alumina with an amount of 0.5% of silica. 

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 sulfur atoms are also clustered in all-cis positions in the txtxp2p2 bicapped trigonal prismatic structure of tetrakis(A-methyl-p-thiotolylhydroxamato)hafnium(IV) [HffMeQJlr C(S)N Oj Me 4]. Averaged metal-ligand bond distances are Iff—0 = 2.150 and Hf—S =... 

High-coordination-number complexes of 0-keto-enolates continue to be obtained with the metals such as zirconium(IV),8 hafnium(IV),8 cerium(IV),9 and the lanthanons(III),10 the last being tetrakis anionic species. At least one example of a volatile tetrakis 0-keto-enolate salt has been reported,11 Cs[Y(CF3-COCHCOCF3)4]. The ionic charge on the 0-keto-enolate complex has been shown to produce12 a high field nuclear magnetic resonance for anions and low field shifts for cations, relative to the positions observed for the neutral species. 

Tetrakis(l, 1,l-trifluoro-2,4-pentanedionato)zirconium (and hafnium), synthesis 14... 

Tetrakis(l,l,l-trifluoro-2,4-pentanedionato)zirconium and (hafnium), S3mthesis 14 Fluorophosphoranes, synthesis 18 Phenyldibromophosphine, synthesis 19 Phosphonitrile fluorides, synthesis 20... 

Hf(C204)4K4-6H20, 8 42 Hf(C5H402Fa)4 Tetrakis(l,l,l-trifluoro-2,4-pentanedionato) hafnium, 9 50 HfCla, 4 121... 

The cubic phases of zirconium- and hafnium nitride display properties quite similar to those of TiN. These compositions have been studied to some extent, however, the number of reports dealing with the CVD of ZrN and HfN is considerably lower than those describing the CVD of TiN. Zirconium and hafnium nitride can be prepared by the decomposition of the appropriate metal tetrakis(dialkylamide) compounds [155]. Zirconium and hafnium nitrides of the stoichiometry M3N4 also have been prepared by CVD. The compounds are formed when M(NEt2)4 is reacted with NH3 at 200-450°C [144]. The films thus produced are crystalline, yellow, transparent and insulating. It has been suggested that these phases are related to the MN phase by a rhombohedral distortion. 

Zirconium and hafnium diboride have been studied less extensively. Zirconium diboride potentially is useful as a coating for solar absorbers [242]. These compositions can be prepared either by hydrogen co-reduction of the metal and boron halides [242], or by the decomposition of the metal tetrakis(tetrahydroborates) M(BH4)4 [241]. 

Tetrakis(acetylacetonato) complexes of zirconium and hafiiium were reported in 1904 and 1926, respectively, and a large number of j3-diketonate derivatives have been described subsequently (Table 10). These compounds are of the type [M(dik)4], [M(dik)3X], [M(dik)2X2], M(dik)X3 and [M(dik)3]Y (dik = -diketonate anion X = C1, Br, I, NO3, or alkoxide Y = [FeCU], [AuCU], [PtCU] or 2[Zr(S04)3]). Additional j3-diketonate compounds include the anionic complex [NEt4][Zr(bzbz)F4] (bzbz = dibenzoylmethanate) and the 1 1 ZrCU-diketone adducts [ZrCl4(MeCOCR2COMe)] (R = H or Me). " Early work on zirconium and hafnium jS-diketonates has been reviewed by Larsen, Bradley and Thornton, Fackler and Mehrotra et al. ... 

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