2081-12-1Relevant articles and documents
Tuning metal stoichiometry in heterometal alkoxides: First structurally characterised molecular precursor to BaZrO3
Veith, Michael,Mathur, Sanjay,Huch, Volker,Decker, Timo
, p. 1327 - 1332 (2007/10/03)
Manipulable metal ratios are accessible in a series of heterometal Ba-Zr alkoxides by changing the size and the charge of the ligands. The synthesis and characterisation of four mixed-metal Ba-Zr species [BaZr2(OtBu)10] (1), [Ba2Zr(OtBu)8(tBuOH)(THF)2] (2), [BaZr(OtBu)6(THF)2] (3) and [BaZr(OH)(OiPr)5(iPrOH)3]2 (4), based on different Ba/Zr stoichiometries, are reported. The molecular structures of 1, 2, and 4 have been determined by single-crystal X-ray diffraction studies. 1 exhibits a bow-tie structural motif in which a trigonally distorted six-coordinate barium atom is chelated by two bipyramidal {Zr(OtBu)5}- units. 2 reveals a triangular Ba2Zr(μ3-OrBu)2(μ 2-OtBu)3 core structure t formed by the fusion of three oclahedra built about two Ba atoms and a Zr atom. The structure is unique in terms of the distribution of terminal ligands at each of the metal centers. One of the barium atoms possesses one -OtBu and one tBuOH as terminal ligands, while the terminal ligands on the second barium atom are two THF molecules; the zirconium center bears -OtBu groups as the terminal ligands. Hydrolysis of compound 3 with one equivalent of water, followed by alcoholysis (iPrOH) of the resulting product, gave 4. The structure of 4 shows a planar tetrametallic Ba2Zr12 frame capped by two μ3-hydroxo ligands. The coordination figure of the zirconium atoms resembles a distorted octahedron, whereas the geometry of the barium centers is best described as capped trigonal prisms. Both 3 and 4 are excellent precursors to morphologically pure BaZrO3 ceramic by the sol-gel process.
Synthesis and Reactivity of Group 4 Homoleptic Selenolates and Tellurolates: Lewis Base Induced Conversion to Terminal and Bridging Chalcogenides
Gerlach, Christopher P.,Christou, Victor,Arnold, John
, p. 2758 - 2766 (2008/10/09)
A combination of either salt metathesis reactions between MCl4 (M = Zr, Hf) and (THF)2LiSeSi(SiMe3)3 (THF = tetrahydrofuran) or between TiCl3(THF)3 and (THF)2LiESi(SiME3)3 (E = Se, Te), or chalcogenolysis reactions between M(CH2Ph)4 (M = Zr, Hf) and HESi(SiMe3)3 (E = Se, Te) afforded the series of compounds M[ESi(SiMe3)3]4 (M = Ti, Zr, Hf; E = Se, Te). The X-ray structures of M[TeSi(SiMe3)3]4 (M = Zr, Hf) and Zr[SeSi(SiMe3)3]4 have been determined and are presented for comparison. Reaction of group 4 tetrabenzyls with 3 equiv of HSeSi(SiMe3)3 gave the complexes M[SeSi(SiMe3)3]3(CH2Ph) (M = Ti, Zr, Hf) in high yields. Treatment of the zirconium and hafnium homoleptic tellurolates with 2 equiv of xylyl isocyanide produced the bis-L trans adducts M[TeSi(SiMe3)3]4[CN(xylyl)]2 (M = Zr, Hf) in moderate yields. The related six-coordinate DMPE adducts M[TeSi(SiMe3)3]4(DMPE) (M = Zr, Hf; DMPE = 1,2-bis(dimethylphosphino)ethane) were similarly prepared. Reaction of the mono-DMPE complexes with a second equilvalent of DMPE led to the elimination of Te[Si(SiMe3)3]2 and the formation of the seven-coordinate bis(tellurolate), bis(DMPE), terminal tellurides M[TeSi(SiMe3)3]2(Te)(DMPE)2 (M = Zr, Hf). Both of the tellurides have been structurally characterized. The homoleptic zirconium selenolate reacts with 1 equiv of DMPE, yielding a bright red material with the stoichiometry Zr[SeSi(SiMe3)3]2(Se)(DMPE). The diphosphine DMPM (DMPM = 1,2-bis(dimethylphosphino)methane) also reacted with M[SeSi(SiMe3)3]4 (M = Zr, Hf) to give the bis(μ-Se), A-frame dimers {M[SeSi(SiMe3)3]2(μ-Se)(μ-η 2-DMPM)}2 (M = Zr, Hf) in relatively low yields (40 and 23percent). The structure of the zirconium derivative has been confirmed using X-ray crystallography. Crystallographic data are as follows: Zr[SeSi(SiMe3)3]4, monoclinic, P21/c, a = 22.6944(34) A?, b = 15.2943(55) A?, c = 22.7758(61) A?, β= 105.695(17)°, Z = 4, R = 5.29, Rw = 3.69; Hf[TeSi(SiMe3)3]4, monoclinic, P21/c, a = 22.494(5) A?, b = 15.609(5) A?, c = 22.742(5) A?, β= 104.480(5)°, Z = 4, R = 4.48, Rw = 5.45; Hf[TeSi(SiMe3)3]2(Te)(DMPE)2, monoclinic, P21, a = 14.795(3) A?, b = 14.289(3) A?, c = 15.4212(2) A?, β= 102.543(3)°, Z = 2, R = 4.78, Rw = 6.70; {Zr[SeSi(SiMe3)3]2(μ-Se)(μ-η 2-DMPM)}2, monoclinic, P21/n, a = 14.7651(13) A?, b = 18.8579(17) A?, c = 18.6072(17) A?, β= 111.031(1)°, Z = 2, R = 8.26, Rw = 8.13.
