Synthesis, Crystal Structures, and Optical and Magnetic Properties of Samarium, Terbium, and Erbium Coordination Entities Containing Mono-Substituted Imine Silsesquioxane Ligands

Mono-substituted cage-like silsesquioxanes of the T₈-type can play the role of potential ligands in the coordination chemistry. In this paper, we report on imine derivatives as ligands for samarium, terbium, and erbium cations and discuss their efficient synthesis, crystal structures, and magnetic and optical properties. X-ray analysis of the lanthanide coordination entities [MCl₃(POSS)₃]·2THF [M = Er³⁺ (3), Tb³⁺ (4), Sm³⁺ (5)] showed that all three compounds crystallize in the same space group with similar lattice parameters. All compounds contain an octahedrally coordinated metal atom, and additionally, 3 and 5 structures are strictly isomorphous. However, surprisingly, there are two different molecules in the crystal structure of the terbium coordination entity 4, monomer (sof 65%) and dimer (sof 35%), with one and two metal centers. Absorption measurements of the investigated materials recorded at 300 K showed that regardless of the lanthanide involved, their energy band gap equals 2.7 eV. Moreover, the analogues containing Tb³⁺ and Sm³⁺ exhibit luminescence typical of these rare earth ions in the visible and infrared spectral range, while the compound with Er³⁺ does not generate any emission. Direct current variable-temperature magnetic susceptibility measurements on polycrystalline samples of 3-5 were performed between 1.8 and 300 K. The magnetic properties of 3 and 4 are dominated by the crystal field effect on the Er³⁺ and Tb³⁺ ions, respectively, hiding the magnetic influence between the magnetic cations of adjacent molecules. Complex 5 exhibits a nature typical for the paramagnetism of the samarium(III) cation.

Heterometallic 3d-4f Alkoxide Precursors for the Synthesis of Binary Oxide Nanomaterials

In this study, a new method for the synthesis of heterometallic 3d-4f alkoxides by the direct reaction of metallic lanthanides (La, Pr, Nd, Gd) with MCl₂ (M = Mn, Ni, Co) in 2-methoxyethanol was developed. The method was applied to the synthesis of the heterometallic oxo-alkoxide clusters [Ln₄Mn₂(μ₆-O)(μ₃-OR)₈(HOR)_xCl₆] (Ln = La (1), Nd (2), Gd (3); x = 0, 2, 4); [Pr₄M₂(μ₆-O)(μ₃-OR)₈(HOR)_xCl₆] (M = Co (4), Ni (5); x = 2, 4); and [Ln₄Mn₂(μ₃-OH)₂(μ₃-OR)₄(μ-OR)₄(μ-Cl)₂(HOR)₄Cl₆] (Ln = La (11) and Pr (12)). Mechanistic investigation led to the isolation of the homo- and heterometallic intermediates [Pr(μ-OR)(μ-Cl)(HOR)Cl]_n (6), [Co₄(μ₃-OR)₄(HOR)₄Cl₄] (7), [Ni₄(μ₃-OR)₄(HOEt)₄Cl₄] (8), [Mn₄(μ₃-OR)₄(HOR)₂(HOEt)₂Cl₄] (9), and [Nd(HOR)₄Cl][CoCl₄] (10). In the presence of an external M(II) source at 1100 °C, 1-4 and 12 were selectively converted into binary metal oxide nanomaterials with trigonal or orthorhombic perovskite structures, i.e., LaMnO₃, GdMnO₃, NdMnO₃, Pr_0.9MnO₃, and PrCoO₃. Compound 5 decomposed into a mixture of homo- and heterometallic oxides. The method presented provides a valuable platform for the preparation of advanced heterometallic oxide materials with promising magnetic, luminescence, and/or catalytic applications.

Use of group 13 aryloxides for the synthesis of green chemicals and oxide materials

In this work, group 13 metal aryloxides [Al(MesalO)3] (1), [Me2Ga(MesalO)]2 (2), [AlLi3(MesalO)6] (3) and [Me2GaLi(MesalO)2(THF)] (4), were obtained by reaction of methyl salicylate (MesalOH) with group-13 alkyls MMe3 (for M...

Synthesis, Crystal Structures, and Spectroscopic Properties of Novel Gadolinium and Erbium Triphenylsiloxide Coordination Entities

In alkali metal and lanthanide coordination chemistry, triphenylsiloxides seem to be unduly underappreciated ligands. This is as surprising as that such substituents play a crucial role, among others, in stabilizing rare oxidation states of lanthanide ions, taking a part of intramolecular and molecular interactions stabilizing metal-oxygen cores and many others. This paper reports the synthesis and characterization of new lithium [Li₄(OSiPh₃)₄(THF)₂] (1), and sodium [Na₄(OSiPh₃)₄] (2) species, which were later used in obtaining novel gadolinium [Gd(OSiPh₃)₃(THF)₃]·THF (3), and erbium [Er(OSiPh₃)₃(THF)₃]·THF (4) configuration, it can result in res were determined for all 1-4 compounds, and in addition, IR, Raman, absorption spectroscopy studies were conducted for 3 and 4 lanthanide compounds. Furthermore, direct current (dc) variable-temperature magnetic susceptibility measurements on polycrystalline samples of 3 and 4 were carried out in the temperature range 1.8-300 K. The 3 shows behavior characteristics for the paramagnetism of the Gd³⁺ ion. In contrast, the magnetic properties of 4 are dominated by the crystal field effect on the Er³⁺ ion, masking the magnetic interaction between magnetic centers of neighboring molecules.

Polyoxometalate-like structure of new potassium triphenylsiloxides: [K6(OSiPh3)6(C3H7OH)(H2O)]·2C6H5CH3 and [K6(OSiPh3)6(H2O)2]

The synthesis and structural characterization of two new potassium triphenylsiloxides, namely, aqua(propan-2-ol)hexakis(triphenylsilanolato)hexapotassium toluene disolvate, [K₆(C₁₈H₁₅OSi)₆(C₃H₈O)(H₂O)]·2C₇H₈, and diaquahexakis(triphenylsilanolato)hexapotassium, [K₆(C₁₈H₁₅OSi)₆(H₂O)₂], are reported. Both compounds crystallize in the triclinic space group P-1. The structure in each case resembles an alkali metal polyoxometalate-like structure, in which electrostatic interactions are observed in the metal-oxygen core. Furthermore, both compounds also resemble a reverse micelles-like architecture, in which the hydrophilic core is enclosed in a hydrophobic shell. The cores of the complexes are flanked by hydrophobic aromatic rings derived from Ph₃SiO^- anions, where intramolecular π-interactions between the aromatic rings and potassium cations stabilize the cores of the crystals. Moreover, in both structures, the presence of hydrogen bonds is observed; until now, no crystal structures have been described containing K atoms and triphenylsiloxide molecules in which the presence of hydrogen bonds was confirmed. Thus, these coordination entities could be considered as attractive reagents for further synthetic protocols towards heterometallic complexes.

Heterometallic Group 4-Lanthanide Oxo-alkoxide Precursors for Synthesis of Binary Oxide Nanomaterials

In this study, an efficient procedure for the synthesis of uncommon group 4-lanthanide oxo-alkoxide derivatives was developed. Heterometallic clusters with the structures [La₂Ti₄(μ₄-O)₂(μ₃-OEt)₂(μ-OEt)₈(OEt)₆(Cl)₂(HOEt)₂] (1), [La₂Zr₂(μ₃-O)(μ-OEt)₅(μ-Cl)(OEt)₂(HOEt)₄(Cl)₄]_n (2), [La₂Hf₂(μ₃-O)(μ-OEt)₅(μ-Cl)(OEt)₂(HOEt)₄(Cl)₄]_n (3), [Nd₂Ti₄(μ₄-O)₂(μ₃-OEt)₂(μ-OEt)₈(OEt)₆(HOEt)₂(Cl)₂] (4), [Nd₄Zr₄(μ₃-O)₂(μ-OEt)₁₀(μ-Cl)₄(OEt)₈(HOEt)₁₀(Cl)₂] (5), and [Nd₄Hf₄(μ₃-O)₂(μ-OEt)₁₀(μ-Cl)₄(OEt)₈(HOEt)₁₀(Cl)₂] (6) were synthesized via the reaction of a metallocene dichloride, Cp₂M'Cl₂ (where M' = Ti, Zr, and Hf), and metallic lanthanum or neodymium in the presence of excess ethanol. This procedure gave crystalline precursors with molecular stoichiometries suitable for obtaining group 4-lanthanide oxide materials. Compounds 1-6 were examined by analytical and spectroscopic techniques and single-crystal X-ray diffraction. The magnetic properties of 5 and 6 were investigated by using direct and alternating current (dc and ac) susceptibility measurements. The results indicated weak antiferromagnetic interactions between Nd^III ions and a field-supported slow magnetic relaxation. Lanthanum-titanium compound 1 decomposed at 950 °C to give the perovskite compound La_0.66TiO₃ and small amounts of rutile TiO₂. Under the same conditions, 4 decomposed to give a mixture of Nd₄Ti₉O₂₄ and Nd_0.66TiO₃. When 4 was calcined at 1300 °C, decomposition of Nd₄Ti₉O₂₄ to Nd_0.66TiO₃ and TiO₂ was observed. Calcination of 2, 3, 5, and 6 at 950-1500 °C led to the selective formation of heterometallic La₂Zr₂O₇, La₂Hf₂O₇, Nd₂Zr₂O₇, and Nd₂Hf₂O₇ phases, respectively.

Convenient Route to Heterometallic Group 4-Zinc Precursors for Binary Oxide Nanomaterials

In this study, simple and efficient synthetic routes to a family of uncommon group 4-zinc heterometallic alkoxides were developed. Single-source molecular precursors with the structures [Cp₂TiZn(μ,η-OR)(THF)Cl₂] (1), [Zr₃Zn₇(μ₃-O)(μ₃,η²-OR)₃(μ-OH)₃(μ,η²-OR)₆(μ,η-OR)₆Cl₆] (2), and [Hf₃Zn₇(μ₃-O)(μ₃,η²-OR)₃(μ-OH)₃(μ,η²-OR)₆(μ,η-OR)₆Cl₆] (3) were prepared via reduction of Cp₂TiCl₂ with metallic zinc or protonolysis of the metal-cyclopentadienyl bond in Cp₂M'Cl₂ (M' = Zr or Hf) in the presence of 2-methoxyethanol (ROH) and Zn(OR)₂. This synthetic route enables the creation of compounds with well-defined molecular structures and therefore provides precursors suitable for obtaining group 4-zinc oxides. Precursors 1-3 were characterized by elemental analysis, nuclear magnetic resonance and infrared spectroscopies, and single-crystal X-ray diffraction. Compound 1 decomposed at 800-900 °C to give a mixture of binary metal oxides (i.e., Zn₂Ti₃O₈, ZnTiO₃, or Zn₂TiO₄) and common polymorphs of TiO₂ and ZnO. After calcination at 1000 °C, only TiO₂ and the high-temperature-stable phase Zn₂TiO₄ were observed. Thermolysis of compounds 2 and 3 gave mixtures of ZnO and ZrO₂ or HfO₂, respectively. The obtained ZnO-ZrO₂ and ZnO-HfO₂ mixed oxide materials have constant phase compositions across a broad temperature range and therefore are attractive host lattices for Eu³⁺ for applications as yellow/red double-light-emitting phosphors. It was established that Eu³⁺ ions were successfully introduced into the ZnO and ZrO₂/HfO₂ lattices. It was revealed that Eu³⁺ ions prefer to occupy low-symmetry sites in ZrO₂/HfO₂ rather than in ZnO.

Structural analysis and catalytic activity of tetranuclear metal carboxylate clusters with a [KZn3(μ3-OH)(OOCCPh3)6] or [Zn4(μ4-O)(OOCCPh3)6] central motif

Tetranuclear triphenylacetato zinc–potassium or zinc clusters of formula [K_xZn_4−x(μ₃-OH)_x(μ₄-O)_1−x(Ph₃CCOO)₆] where x = 0, 1, with interesting structural, physicochemical or catalytic properties were obtained.

Transformation of molecular compounds with Ba(Sr)/Al/Si and Ca(Sr, Ba)/Ti(Zr, Hf)/Si heteroelements as new efficient route to metal silicate materials

Silicon-based moieties were anchored in heterometallic alkoxide platforms to obtain molecular clusters based on the M-O-M'-O-Si motif for the generation of mixed-metal silicate materials. Single-source molecular precursors with structures [M{(μ-ddbfo)2Al(OSiPh3)2}2], where dbbfoH = 2,3-dihydro-2,2-dimethylbenzofuran-7-ol and M = Ba (1), Sr (2), [Sr4Ti2(μ6-O)(μ3,η2-OCH2CH2OMe)8(η-OCH2CH2OMe)2(OSiPh3)4] (3), [Sr4M'2(μ4-OH)(μ3,η2-OCH2CH2OMe)4(μ,η2-OCH2CH2OMe)6(μ-X)(OSiPh3)4] (4, with M' = Zr and X = Cl; 5 with M' = Hf and X = OH), [Sr3Hf2(μ5-O)(μ3,η2-OCH2CH2OMe)4(OCH2CH2OMe)4(OSiPh3)4] (6), and [Ca2M'2(μ3-OH)2(μ,η2-OCH2CH2OMe)4(η2-HOCH2CH2OMe)2(η-OCH2CH2OMe)2(OSiPh3)4] for M' = Zr (7), Hf (8), were prepared by substitution of methyl groups, using Ph3SiOH or chloride atoms with KOSiPh3, in [M{(μ-ddbfo)2AlMe2}2] (M = Sr, Ba) or [M4M'2(μ6-O)(μ3,η2-OCH2CH2OMe)8(OCH2CH2OMe)2(HOCH2CH2OMe)xCl4] (M = Ca, Sr, Ba, M' = Ti, Zr, Hf and x = 0, 4). The precursors were characterized by elemental analysis, NMR spectroscopy, and single-crystal X-ray structural analysis. Thermal decomposition of compounds 1-8 at 1000 °C led to formation of ceramic materials that consisted of mixed-metal oxide nanocrystallites embedded in an amorphous SiO2 matrix. Compounds 1 and 2 decomposed to BaAl2Si2O8 and SrAl2Si2O8 aluminosilicates, 4 gave a mixture of SrSiO3, ZrO2, SrZrO3 and Sr7ZrSi6O21, 5 and 6 gave mixtures of various compounds, including SrHfO3, Hf0.96Si0.04O2, and SiO2, 7 lead to CaZrO3, ZrO2 and Ca3ZrSi2O9 and 8 gave a HfO2, Ca2HfSi4O12 and SiO2 phase. The thermolysis of compound 3 gave SiO2 particles of average size 40-90 nm, which contained spherical SrTiO3, SrSiO3 and Sr2TiSi2O8 nanocrystallites of diameter 5-16 nm.

Correction: New tetranuclear manganese clusters with [MnII3MnIII] and [MnII2MnIII2] metallic cores exhibiting low and high spin ground state

Correction for ‘New tetranuclear manganese clusters with [Mn^II₃Mn^III] and [Mn^II₂Mn^III₂] metallic cores exhibiting low and high spin ground state’ by M. Sobocińska et al., Dalton Trans., 2016, 45, 7303–7311.

New tetranuclear manganese clusters with [MnII3MnIII] and [MnII2MnIII2] metallic cores exhibiting low and high spin ground state

Two tetranuclear mixed-valent clusters with the metallic [MnII3Mn^III] and [MnII2MnIII2] cores were synthesized as molecular nanomagnets with the low and high spin in the ground state.

Crystal structure of a mixed-ligand dinuclear Ba-Zn complex with 2-meth-oxy-ethanol having tri-phenyl-acetate and chloride bridges

The dinuclear barium-zinc complex, μ-chlorido-1:2κ(2) Cl:Cl-chlorido-2κCl-bis-(2-meth-oxy-ethanol-1κO)bis-(2-meth-oxy-ethanol-1κ(2) O,O')bis-(μ-tri-phenyl-acetato-1:2κ(2) O:O')bariumzinc, [BaZn(C20H15O2)2Cl2(C3H8O2)4], has been synthesized by the reaction of barium tri-phenyl-acetate, anhydrous zinc chloride and 2-meth-oxy-ethanol in the presence of toluene. The barium and zinc metal cations in the dinuclear complex are linked via one chloride anion and carboxyl-ate O atoms of the tri-phenyl-acetate ligands, giving a Ba⋯Zn separation of 3.9335 (11) Å. The irregular nine-coordinate BaO8Cl coordination centres comprise eight O-atom donors, six of them from 2-meth-oxy-ethanol ligands (four from two bidentate O,O'-chelate inter-actions and two from monodentate inter-actions), two from bridging tri-phenyl-acetate ligands and one from a bridging Cl donor. The distorted tetra-hedral coordination sphere of zinc comprises two O-atom donors from the tri-phenyl-acetate ligands and two Cl donors (one bridging and one terminal). In the crystal, O-H⋯Cl, O-H⋯O and C-H⋯Cl inter-molecular inter-actions form a layered structure, lying parallel to (001).

Cyclopentadienyl/alkoxo ligand exchange in group 4 metallocenes: a convenient route to heterometallic species

A simple and efficient strategy for the synthesis of nonorganometallic heterometallic clusters from cheap organometallic precursors is reported. This unique synthetic method involves elimination of the cyclopentadienyl ring from Cp(2)MCl(2) (M = Ti, Zr, Hf) as CpH in the presence of M'L(2) or M'L'(2) (M' = Ca, Sr, Mn; CH(3)OCH(2)CH(2)OH = LH or (CH(3))(2)NCH(2)CH(2)OH = L'H) in an alcohol as a source of protons. In the reactions presented, a series of compounds, [Ca(4)Ti(2)(mu(6)-O)(mu(3),eta(2)-L)(8)(eta-L)(2)Cl(4)] (1), [Sr(4)Hf(2)(mu(6)-O)(mu(3),eta(2)-L)(8)(eta-L)(2)(eta-LH)(4)Cl(4)] (2), [Ca(4)Zr(2)(mu(6)-O)(mu-Cl)(4)(mu,eta(2)-L)(8)Cl(2)] (3), [Sr(4)Ti(2)(mu(6)-O)(mu(3),eta(2)-L)(8)(eta-L)(2)(eta-LH)(2)Cl(4)] (4), [Ca(4)Zr(2)Cp(2)(mu(4)-Cl)(mu-Cl)(3)(mu(3),eta(2)-L)(4)(mu,eta(2)-L)(4)Cl(2)] (5), [CaTiCl(2)(mu,eta(2)-L')(3)(eta-L'H)(3)][L'] (6), [Ca(2)Ti(mu,eta(2)-L')(6)Cl(2)] (7), [Mn(4)Ti(4)(mu-Cl)(2)(mu(3),eta(2)-L)(2)(mu,eta(2)-L)(10)Cl(6)] (8), and [Mn(10)Zr(10)(mu(4)-O)(10)(mu(3)-O)(4)(mu(3),eta(2)-L)(2)(mu,eta(2)-L)(16)(mu,eta-L)(4)(eta-L)(2)Cl(8)] (9), were obtained in good yield. All of the complexes were characterized by elemental analysis, IR and NMR spectroscopy, and single-crystal X-ray structural analysis. Complex 8 belongs to a group of magnetic clusters that consists of Mn(4) subunits held together by two mu-Cl bridges. Compounds 6 and 7 underwent thermal decomposition, yielding an alternative source for some heterometallic oxides, which were analyzed by X-ray powder diffraction.

cis-Dichloridobis[2-(hydroxy-meth-yl)tetra-hydro-furan-κO,O']manganese(II)

The structure of the title compound, [MnCl(2)(C(5)H(10)O(2))(2)], was solved from low-temperature data collected at 100 (2) K. The asymmetric unit contains one half-mol-ecule with the Mn(II) ion located on a twofold axis. A distorted octa-hedral environment around the Mn atom is formed by two ether and two hydroxyl O atoms of two 2-(hydroxy-methyl)tetra-hydro-furan ligands, and by two chloride ions. The chelating tetra-hydro-furan ligands, which form five-membered rings, are cis oriented. The crystal structure is stabilized by hydrogen bonding between the coordinated OH groups and the chloride ions.

A pentanuclear bimetallic complex of manganese(II) and aluminium(III) ions: tetra-mu2-iodido-iodidobis(mu3-2-methoxyethanolato)bis(mu2-2-methoxyethanolato)dimethyl(tetrahydrofuran-kappaO)aluminium(III)tetramanganese(II)

The molecule of the title compound, [Mn(4)Al(CH(3))(2)(C(3)H(7)O(2))(4)I(5)(C(4)H(8)O)], contains one Al(III) and four Mn(II) ions. Two Mn atoms are five-coordinate in the form of a trigonal bipyramid or a square pyramid. The two other Mn atoms are six-coordinate with an octahedral geometry. The fourcoordinate Al atom is linked to the manganese core by mu-O(alkoxo) bridges, forming an almost planar five-membered ring.

Titanium−Manganese Compound with a Chiral Mn3Ti Center

We have shown here for the first time a facile route to the molecular compound [Mn3Ti(mu3-OCH2CH2OCH3)2(mu-OCH2CH2OCH3)3(mu-Cl)Cl2(OiPr)2] with a Mn3Ti motif, where the Ti atom is in the chiral position and the Mn atoms occupy nonchiral sites.

Syntheses, structure, and properties of a manganese–calcium cluster containing a Mn4Ca2core

We describe here a novel, simple, efficient self-assembly method for the in situ generation of [Mn4Cl4(micro-OCH2CH2OMe)4(EtOH)4] and [Mn4(micro-Cl)Cl3(micro-OCH2CH2OMe)4(HOCH2CH2OMe)3]2 cubane-type compounds which react readily with calcium species to form cluster [Mn4Ca2Cl4(micro-OCH2CH2OMe)8], the calcium atoms attached to the Mn4 unit of flatten out the cubane inducing significant conformational changes.

Deoligomerization by Cocomplexation: Syntheses and Structures of Aluminum−Calcium Alkoxides and Aryloxides

Reactions of oligomeric "Ca(dbbfo)2" and Ca9(CH3OCH2CH2O)18(CH3OCH2CH2OH)2 with Al(CH3)3 in toluene gave tetranuclear heterobimetallic [Ca(mu-dbbfo){(mu-dbbfo)(mu-CH3)Al(CH3)2}]2 (71%) and polymeric Ca{(mu-CH3OCH2CH2O)(mu-CH3)Al(CH3)2}2 (86%). The latter can be obtained as monomeric THF adduct Ca{(mu-CH3OCH2CH2O)Al(CH3)3}2(THF)2 (78%) when a mixture of solvents is used. The results, including an initial L-lactide polymerization test, are discussed in the context of calcium alkoxo cluster degradation in solution.

Structural Characterization of a Methylaluminoxane (MAO)−Magnesium Dichloride Cluster: Model of MAO Grafted onto a MgCl2 Support

The study outlines our initial results that contribute to a better understanding of MAO/MgCl2 (MAO=methylaluminoxane) incorporation in the Cp2ZrCl2/MAO/MgCl2 catalytic system, which is currently of global industrial use. We show here that the[Al3(mu3-O)(Me)5]2+ moiety can be trapped by the tetrapodal [Mg3Cl4(thffo)4(THF)]2- macrounit to form a cluster [Al3Mg3(mu3-O)(thffo)4(Me)5Cl4(THF)] (thffo=2-tetrahydrofurfuroxide). From this perspective, this macrounit might be considered as a part of the MgCl2 support surface, which fulfills the requirement of a Al3(mu3-O) core.

Synthesis of Homoleptic Barium Alkoxides and Aryloxides and Their Reactions with Al(CH3)3: a Convenient Route to Heterometallic Species

Reactions of metallic Ba with benzofuranol (dbbfoH) or diethylene glycol give homoleptic and homonuclear complexes Ba(dbbfo)(2)(dbbfoH)(2).3dbbfoH and Ba{O(CH(2)CH(2)O)(2)}{O(CH(2)CH(2)OH)(2)}(2) (60-89%). Both compounds and formerly described Ba{O(CH(2)CH(2)O)(2)Me}(2) react with Al(CH(3))(3) to yield trinuclear heterobimetallic low-coordinated barium compounds with structure and geometry depending on the reaction stoichiometry and crystallization procedure.

The first structurally characterized nonorganometallic titanium(III) alkoxo-bridged dinuclear complexes

The reaction of [Ti4(OMe)14Cl2] (1) with an excess of AlMe3 gave the cocrystallite [Ti2(mu-OMe)2(mu-Cl)Cl3(thf)3].[Ti2(mu-OMe)3Cl3(thf)3] (2.3) species in a 1:1 ratio. Similar to 2, [Ti2(mu-OEt)2(mu-Cl)Cl3-(thf)3] (4) was obtained in the reaction of an equimolar mixture of TiCl4 and Ti(OEt)4 with Al/AlMe3. The short distance [2.543(1)av A in 2.3 and 2.599(1) A in 4] between "Ti(+3)" atoms, their diamagnetism, and ELF analysis indicate the presence of a Ti-Ti bond.

A family of Group 4 metal alkoxo complexes with an M3(mu3-O) core relevant to Ziegler-Natta catalyst intermediates

Reactions of [Mg(thffo)(2)] (1) or [Ca(thffo)(2)] (2) with ZrCl(4) or HfCl(4) in a CH(2)Cl(2)/THF/CH(3)CN mixture give thermally stable neutral heterobimetallic tetranuclear complexes [M(3)M'(mu(x)-O)(mu,eta(2)-thffo)(6)(Cl)(6)] (thffo=tetrahydrofurfuroxide; M/M'/x: 3, Zr/Mg/3; 4, Hf/Mg/3; 5, Zr/Ca/4; 6, Hf/Ca/4) as colorless crystals in 75-82 % yield. X-ray diffraction studies show complexes 3-5 to contain oxo-bridged M(3) triangles that are capped by an alkaline earth metal-containing moiety to form species of C(3) symmetry. Reactions of ZrCl(4) and HfCl(4) with pure tetrahydrofurfuryl alcohol in EtOH and MeOH provide ionic complexes [M(3)(mu(3)-O)(mu,eta(2)-thffo)(3)(L)(3)(Cl)(6)]Cl (M/L: 8, Zr/EtOH; 9, Hf/EtOH; 10, Zr/MeOH) in 66-79 % yield. Complexes 8-10 consist of M(3) triangles that are analogous to those in 3-6 and possess similar overall symmetry, as shown by X-ray crystallography. Changes in the reaction conditions afforded the asymmetric neutral dimer [Zr(2)(mu-thffo)(2)(thffoH)(Cl)(6)] (7) and the homometallic [Zr(3)(mu(3)-O)(mu,eta(2)-thp)(3)(thf)(2)(Cl)(7)] (11).

Syntheses, structure, and reactivity of chiral titanium compounds: procatalysts for olefin polymerization

Titanium complexes with chelating alkoxo ligands have been synthesised with the aim to investigate titanium active centres in catalytic ethylene polymerisation. The titanium complexes cis-[TiCl2(eta2-maltolato)2] (1, 89%), and cis-[TiCl2(eta2-guaiacolato)2] (2, 80%) were prepared by direct reaction of TiCl4 with maltol and guaiacol in toluene. The addition of maltol to [Ti(OiPr)4] in THF results in the formation of species [Ti(OiPr)2(maltolato)2] (3, 82%). The titanium compound cis-[Ti(OEt)2(eta2-maltolato)2] (4, 74%) was obtained by the transesterification reaction of species 3 with CH3CO2Et. When compound 4 is dissolved in THF a dinuclear species [Ti2(mu-OEt)2(OEt)4-(eta2-maltolato)2] (5, 45%) is formed. Reaction of [Ti(OiPr)4] with crude guaiacol in THF yields a solid, which after recrystallisation from acetonitrile gives [Ti4(mu-O)4(eta2-guaiacolato)] x 4CH3CN (6, 55%). In contrast, reaction of TiCl4 with crude guaiacol in tetrahydrofuran affords [Ti2(mu-O)Cl2(eta2-guaiacolato)4] (7, 82%). Crystallographic and electrochemical analyses of these complexes demonstrate that maltolato and guaiacolato ligands can be used as a valuable alternative for the cyclopentadienyl ring. These complexes have been shown to be active catalysts upon combination with the appropriate activator.

Polynuclear magnesium and magnesium-titanium species. Syntheses and crystal structures of [Mg4(mu3,eta2-ddbfo)2(mu,eta2-ddbfo)2(mu,eta1-ddbfo)29eta1-ddbfo2],

Tetranuclear magnesium complexes with chelating alkoxo ligands have been synthesized with the aim of investigating coordinatively unsaturated magnesium sites able to bind TiX4 (X = Cl, OR), of the type necessary for the formation of the active centers in polymerization catalysts. The magnesium compound [Mg4(mu3,eta2-ddbfo)2(mu,eta2-ddbfo)2(mu,eta1-ddbfo)2(eta1-ddbfo)2] x 2CH2Cl2 (1) (ddbfo = 2,3-dihydro-2,2-dimethyl-7-benzofuranoxide) was prepared by the reaction of MgBu2 with ddbfoH in dichloromethane. Complex 1 exists as a centrosymmetric tetranuclear species with two different types of magnesium centers corresponding to octahedral MgO6 and trigonal bipyramidal MgO5 geometry. Compound 1 is monoclinic, space group P2(1/c), with a = 12.053(2) A, b = 13.323(3) A, c = 17.069(3) A, beta = 98.50(3) degrees , and Z = 4. The reaction of 1 with methanol in tetrahydrofuran (THF) gave compound [Mg4(mu3-OMe)2(mu,eta2-ddbfo)2(mu,eta1-ddbfo)2(eta1-ddbfo)2(CH3OH)5] x CH3OH x THF (2). During this reaction one of the two five-coordinate MgO5 centers in 1 is completed by a methanol molecule and becomes octahedral in 2. Species 2 belongs to the P2(1/n) monoclinic space group, with a = 13.323(3) A, b = 20.768(4) A, c = 27.584(6) A, beta = 104.26(3) degrees , and Z = 4. Compound [Mg4(mu3,eta2-thffo)2(mu,zeta2-thffo)2(mu,eta1-thffo)2[mu-OTi(DIPP)3]2] x 2CH2Cl2 (3) is formed as a result of substitution of two thffo (thffo = 2-tetrahydrofurfuroxide) ligands bonded to the five-coordinate magnesium atom in [Mg4(thffo)8] by bulky OTi(DIPP)3 (DIPP = diisopropylphenolate) groups. Crystals of 3 are monoclinic, space group P2(1/n), with a = 17.069(3) A, b = 18.421(4) A, 17.815(4) A, beta = 90.77(3) degrees , and Z = 4. The X-ray crystal structures of complexes 1-3 are discussed in terms of explaining the role of the coordinatively unsaturated magnesium site in chiral catalyst active center formation.