Renée Papiernik

Molecular precursors of bismuth oxides ; β-diketonates and alkoxides. Molecular structure of [Bi2(μ2,η1-OC2H4OMe)4(η1-OC2H4OMe)2]∞ and of Bi(OSiPh3)3(THF)3

Abstract Various routes to bismuth(III) alkoxides and β-diketonate derivatives have been investigated. Metathesis reactions of the halides and the appropriate sodium derivative offered [Bi(OtBu)3]∞ (1), [Bi2(OC2H4OMe)6]∞ (2), [Bi(OSiPh3)3]m and Bi(dpm)3 (dpmH = dipivaloylmethane) in good yields. The alkoxides display different physical properties; 1 has good volatility, while 2 is highly soluble. Complex 2 and Bi(OSiPh3)3(THF)3 (3) have been characterized by X-ray diffraction. Compound 2 shows a one-dimensional extended “skew” chain structure based on dimeric asymmetric Bi2(μ2,η1-OC2H4 OMe)4(OC2H4OMe)2 units. The alkoxo functionality leads to a distorted pyramidal tetragonal surrounding, but the ether functionality of the bridging groups provides further oxygen donors, and thus coordination numbers of seven and even eight are reached. Bi(OSiPh3)3(THF)3 is monomeric wi th a capped octahedron geometry around the metal. The thermal stability of the volatile precursors 1 and Bi(dpm)3 is in favour of the alkoxide, while the high solubility of 2 is attractive for sol-gel purposes.

Synthesis and molecular structure of Cd9(OC2H4OMe)18,2HOC2H4OMe, the first cadmium aggregate based on oxygen donor ligands

Abstract The alcoholysis reactions between Cd[N(SiMe3)2]2 and functional alcohols such as 2-methoxyethanol produced soluble cadmium alkoxides. Cd9(OC2H4OMe)18, 2HOC2H4OMe has been characterized by X-ray diffraction. The compound corresponds to a centrosymmetric compact aggregate of nine cadmium atoms, the metals being hexa- or pseudo-hexa-coordinated. The alcohol molecules are hydrogen bonded to the terminal alkoxide groups. 113Cd NMR established that the Cd9 cluster was retained in solution.

Heavy main group molecular precursors of oxides: volatile and soluble lead(II) alkoxides and oxoalkoxides

The two products were characterized by elemental analysis, molecular weight data, IR and NMR spectroscopy. [Pb(OBu t ) 2 ] 2 and Pb 4 O(OBu t ) 6 are white air-sensitive solids, both highly soluble in the unual solvents, including hexane

Solution routes to lead titanate: synthesis, molecular structure and reactivity of the Pb–Ti and Pb–Zr species formed between various lead oxide precursors and titanium or zirconium alkoxides. Molecular structure of Pb2Ti2(μ4 -O)(OAc)2(OPri)8 and of PbZr3(μ4-O)(OAc)2(OPri) 10

The reactions between Ti(OR) 4 (R = Et, Pr 1 ) or [Zr(OPr 1 ) 4 (Pr 1 OH)] 2 and various lead oxide precursors [anhydrous Pb(OAc) 2 , alkoxides or oxoalkoxides] have been investigated in different experimental conditions (solvent, temperature). Various mixed-metal species have been isolated in high yields and characterized by microanalysis, FTIR and multinuclear NMR ( 1 H, 13 C and 207 Pb) spectroscopies. The mixed-metal oxoacetatoalkoxides Pb 2 Ti 2 (μ 4 -O)(μ-OAC) 2 (μ-OPr i ) 5 (OPr i ) 3 1 and PbZr 3 (μ 4 -O)(μ-OAc) 2 (μ-OPr i ) 5 (OPr i ) 5 2 have been characterized by X-ray crystallography at -100°C: for 1, monoclinic, space group C 2 /c with a= 38.916(17) A, c = 12.045(2) A, c = 19.046(4) A, β= 112.84(3)°, V=8224(4)A 3 , Z = 8, R = 0.068, R w = 0.076; and for 2, monoclinic, space group P2 1 /n with a=10.618(2) A, b=25.157(11) A, β=18.611(5)1, β=90.35(2)°, V=4971(3)A 3 , Z=4, R =0.060, R w = 0.072. Hydrolysis-condensation reactions have been achieved especially for the species having a Pb: Ti stoichiometry appropriate for access to PbTiO 3 . Effects of the solvent on the temperature of crystallisation and on the particle size are discussed.

Chemical routes to oxides: alkoxidevs. alkoxide–acetate routes: synthesis, characterization, reactivity and polycondensation of MNb2(OAc)2(OPri)10(M=Mg, Cd, Pb) species

The molecular constitution of solutions containing niobium alkoxides and divalent metal acetates M(OAc)2 (M=Mg, Ba, Pb, Zn, Cd) has been examined. The heterometallic aggregates MNb2(µ-OAc)2(µ-OPri)4(OPri)6 (M=Mg 1, Cd 2, Pb 3a) have been isolated and characterized by elemental analysis, FTIR, multinuclear NMR (1H, 13C, 207Pb, 113Cd) and by single-crystal X-ray diffraction for M=Mg and Cd. The magnesium derivative crystallizes in the monoclinic system, space group P21 /c with the unit-cell parameters a=21.238(5), b=10.127(10), c=24.861(3) A, β=107.77(2)° and Z=4. The thermal stability of the various species has been investigated. Condensation is induced thermally for PbNb2(OAc)2(OPri)10 . The reactivity between MNb2(µ-OAc)2- (µ-OPri)4(OPri)6 (M=Pb, Mg) and other metallic species has been evaluated. A terheterometallic compound, PbMgNb2O(OAc)2(OPri)10 has been isolated. Whereas no reaction is observed between Ba(OAc)2 and Nb(OPri)5 , the reaction between metal alkoxides affords BaNb2(OPri)12(PriOH)2 . Its reactivity shows that the absence of an assembling acetate ligand induces facile separation between the metals. Results of the hydrolysis experiments of 1–3a are given. The powders have been analyzed by TG, SEM–EDX, light scattering and XRD. The merit of the assembling acetate ligand for avoiding the segregation of the metals is emphasized.

Molecular precursors of bismuth oxide. Synthesis and structure of [Bi2(µ2-OC2H4OMe)4(OC2H4OMe)2]∞, a one-dimensional ribbon-like chain

Compounds [Bi(OBut)3]∞ and [Bi2(µ2-OC2H4OMe)4(OC2H4OMe)2]∞ have been obtained by metathesis reactions between bismuth halides and the appropriate alkali alkoxides; X-ray structure analysis shows a one-dimensional extended ‘skew’ chain structure based on dimeric asymmetric Bi2(OC2H4OMe)6 units in which the metal displays a pyramidal tetragonal surrounding, with a small number of additional neighbours.

Lead(II) oxoalkoxides as complex ligands: synthesis and molecular structure of the first heterometallic oxoalkoxide, Pb6Nb4(µ4-O)4(µ3-OEt)4(µ2-OEt)12(OEt)8

The compound Pb6Nb4(µ4-O)4(µ3-OEt)4(µ2-OEt)12(OEt)8 has been obtained in 46% yield by reaction between Pb4O(OEt)6 and Nb2(OEt)10 in ethanol at room temperature; its X-ray structure analysis shows an octahedral Pb6 framework, four of the faces of this octahedron being capped by a µ4-oxo ligand connected to a Nb(OEt)5 moiety, and the overall structure can be viewed as a complex of the tetradentate ligand Pb6(µ3-O)4(µ3-OEt)4.

A novel example of self-assembly in lanthanide chemistry: synthesis and molecular structure of [Na(EtOH)6][Y9(µ4-O)2(µ3-OH)8{µ-η2-MeC(O)CHC(O)OEt}8{η2-MeC(O)CHC(O)OEt}8]†

The reaction between yttrium nitrate pentahydrate and the sodium salt of allyl acetatoacetate afforded nonanuclear cluster anions [Y9(µ4-O)2(µ3-OH)8{MeC(O)CHC(O)Z}16]–, the functional group Z being the initial allyl one OCH2CHCH2 or an ethoxide depending on the experimental conditions.

Metal-assisted activation of the C–O bond of 2-hydroxyethylmethacrylate. Synthesis and molecular structure of Ti5(OPri)9(µ-OPri)(µ,η2-OC2H4O)(µ3,η2-OC2H4O)3(µ4,η2-OC2H4O)

Ti5(OPri)9(µ-OPri)(OC2H4O)5 is formed by the reaction between Ti(OPri)4 and 2-hydroxyethylmethacrylate in toluene at room temperature; the pentanuclear aggregate is asymmetric with the titanium atoms displaying coordination numbers of five, six and seven.

Molecules with polymerizable ligands as precursors to porous doped materials

Titanium and aluminum alkoxide derivatives with polymerizable ligands such as 2-(methacryloyloxy)ethylacetoacetate (HAAEMA), oleic acid and geraniol (HOGE) have been obtained. The various compounds have been characterized by FT-IR and NMR {sup 1}H. Copolymerization with styrene and divinylbenzene affords porous doped organic materials which have been characterized by scanning electron microscopy (SEM), elemental analysis, density measurements.