Alkali Metal Induced Structural Changes in Complexes Containing Anionic Lanthanum Aryloxide Moieties. X-ray Crystal Structures of (THF)La(OAr)2(μ-OAr)2Li(THF), (THF)La(OAr)2(μ-OAr)2Na(THF)2, and CsLa(OAr)4 (Ar = 2,6-i-Pr2C6H3)

A convenient and quantitative route to Sn(iv)–M [M = Ti(iv), Nb(v), Ta(v)] heterobimetallic precursors for dense mixed-metal oxide ceramics

Simplicity is beauty. Reactions of SnCl₄ with M(OR)_x yield novel heterobimetallics with simple addition formula.

Structural variation in cerium aryloxide complexes templated by hemilabile K+–amine interactions

Variation of aryloxide substituents using the cerium bdmmp framework provided a structural diversity for study by NMR, crystallography and electrochemistry.

Synthesis and characterization of bimetallic lanthanide-alkali metal complexes stabilized by aminophenoxy ligands and their catalytic activity for the polymerization of 2,2-dimethyltrimethylene carbonate

Electronic properties of the aminophenolate groups have obvious effect on the synthesis of aminophenolate lanthanide-lithium complexes. Amine elimination reactions of Ln[N(SiMe3)2]3(μ-Cl)Li(THF)3 with lithium aminophenolates [ArNHCH2(3,5-(t)Bu2C6H2-2-O)Li(THF)]2 (Ar = p-ClC6H4, [ONH](Cl-p); p-BrC6H4, [ONH](Br-p)) in tetrahydrofuran (THF) in a 1 : 2 molar ratio gave the bimetallic lanthanide-lithium amido complexes [NO](Cl-p)2Ln[N(SiMe3)2][Li(THF)]2 (Ln = Y (1), Yb (2)), and [NO](Br-p)2Ln[N(SiMe3)2][Li(THF)]2 (Ln = Y (3), Yb (4)). When the Ar groups are p-MeOC6H4, ([ONH](MeO-p)) and o-MeOC6H4 ([ONH](MeO-o)), similar reactions generated the homoleptic lanthanide-lithium complexes [NO](MeO-p)3Ln[Li(THF)]3 (Ln = Y (5), Yb (6)) and [NO](MeO-o)2Ln[Li(THF)] (Ln = Y (7), Yb (8)) in high isolated yields, respectively. Whereas the bimetallic lanthanide-lithium amido complexes [NO](Cl-o)2Ln[N(SiMe3)2][Li(THF)]2 (Ln = Y (9), Yb (10)) can be obtained in good yields, when the Ar group is o-ClC6H4 ([ONH](Cl-o)). All of these complexes were well characterized. X-ray structure determination revealed that these complexes have solvated monomeric structures. In complexes 1-4, 9, and 10, the lanthanide atom is five-coordinated by two oxygen atoms and two nitrogen atoms from two aminophenoxy ligands and one nitrogen atom from N(SiMe3)2 group to form a distorted trigonal bipyramidal geometry, whereas in complexes 5-8, the central lanthanide atom is six-coordinated by oxygen atoms, and nitrogen atoms from the aminophenoxy ligands to form a distorted octahedron. It was found that complexes 1-10 are highly efficient initiators for the ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC), affording the polymers with high molecular weights, and the homoleptic heterobimetallic lanthanide complexes showed apparently high activity.

Novel heteroleptic heterobimetallic alkoxide complexes as facile single-source precursors for Ta(5+) doped TiO(2)-SnO(2) nanoparticles

The nanometric mixed tin-titanium oxide doped with a M(5+) cation was recently shown as a promising thermoelectric material. We report here synthesis of novel molecular precursors for above material using a convenient approach of reacting a metal chloride with a metal alkoxide. Heterometallic complexes with simple addition formula [(EtOH)(2)(OEt)(2)Ti(μ-OEt)(2)SnCl(4)] (1·EtOH) and [(EtOH)(OEt)(3)Ta(μ-OEt)(2)SnCl(4)] (2) were isolated in quantitative yield, which on recrystallization from isopropanol afforded mixed-alkoxide complexes [(Pr(i)OH)(2)(OPr(i))(2)Ti(μ-OEt)(2)SnCl(4)] (3) and [(Pr(i)OH)(OPr(i))(3)Ta(μ-OEt)(2)SnCl(4)] (4), respectively, thus indicating the robustness of the heterometallic M(μ-OEt)(2)Sn core in the solution phase. Facile conversion of these precursors to halide-free spinodal form of Ta(5+)-doped TiO(2)-SnO(2) as a potential thermoelectric material is reported.

Synthesis, Reactivity, and Structural Characterization of Sodium and Ytterbium Complexes Containing New Imidazolidine-Bridged Bis(phenolato) Ligands

A new imidazolidine-bridged bis(phenol) [ONNO]H2 ([ONNO]H2=1,4-bis(2-hydroxy-3,5-di-tert-butyl-benzyl)imidazolidine) was prepared in relatively high yield by Mannish reaction of 2,4-di-tert-butylphenol, formaldehyde, and ethylenediamine in a 2:3:1 molar ratio. Reaction of the bis(phenol) with NaH in THF, after workup, afforded the sodium bis(phenolate) {[ONNO]Na2(THF)2}2.2THF (1) as a dimeric tetranuclear complex in an almost quantitative yield. Reaction of YbCl3 with complex 1 in a 2:1 molar ratio in THF, in the presence of HMPA, produced the desired bis(phenolate) ytterbium dichloride as bimetallic complex [ONNO]{YbCl2(HMPA)}2.2.5C7H8 (2). Complex 2 can be used as a precursor for the synthesis of ytterbium derivatives by salt metathesis reactions. Reaction of complex 2 with NaOiPr in a 1:2 molar ratio in THF led to the formation of bimetallic alkoxide [ONNO]{Yb(mu-OiPr)Cl(HMPA)}2.THF (3). However, the residual chlorine atoms in complex 3 are inactive for the further substituted reaction. Further study revealed that the bulkiness of the reagent has profound effect on the outcome of the reaction. Complex 2 reacted with bulky NaOAr (ArO=2,6-di-tert-butyl-4-methylphenoxo) or NaNPh2 in a 1:2 molar ratio under the same reaction conditions, after workup, to give the ligand redistributed products, (ArO)2YbCl(HMPA)2 (4) and [ONNO]YbCl(HMPA)2 (5) for the former and complexes 5 and (Ph2N)2YbCl(HMPA)2 (6) for the latter. If the molar ratio of complex 2 to NaNPh2 decreased to 1:4, the expected ligand redistributed products [ONNO]YbNPh2(HMPA) (7) and (Ph2N)3Yb(HMPA)2.C7H8 (8) can be isolated in high yields. All of the complexes were well characterized, and the definitive molecular structures of complexes 1-4, 7, and 8 were provided by single-crystal X-ray analysis.

Group I cation templated formation of luminescent mono- and bis-substituted thionaphthol heterobimetallic complexes of Pr, Nd, Eu and Tb

Metathesis of lanthanide tris di-tert-butyl beta-diketonates ([Ln(thd)3] Ln=Pr, Nd, Eu, Tb) with one or two equivalents of group 1 salts of the sulfur bridged binaphtholate dianion [1,1'-S(2-OC10H4But(2)-3,6)2]2-, [M2L], M=K, Li affords luminescent mono- and bis-ligand substituted complexes ML[LnL(thd)2].L; M=K, Ln=Pr , Nd , Eu and Tb (L=thf, diethyl ether or toluene) and M(thf)2[LnL2(thd)]; M=Li, Ln=Pr , Nd , Eu , Tb . The potassium salt [K2L] affords mono-L substituted complexes most cleanly, while the lithium salt [Li2L] yields the bis-L substituted complexes most cleanly. The L ligands function as antenna for the sensitised lanthanide-centred emission in Eu3+ and Tb3+ complexes. The X-ray single-crystal structures of mono- and bis-L lanthanide complexes of Nd3+ are presented.

Synthesis and characterization of new biphenolate and binaphtholate rare-Earth-metal amido complexes: catalysts for asymmetric olefin hydroamination/cyclization

Monomeric diolate amido yttrium complexes [Y[diolate][N(SiHMe(2))(2)](thf)(2)] can be prepared in good yield by treating [Y[N(SiHMe(2))(2)](3)(thf)(2)] with either 3,3'-di-tert-butyl-5,5',6,6'-tetramethyl-1,1'-biphenyl-2,2'-diol (H(2)(Biphen)), 3,3'-bis(2,4,6-triisopropylphenyl)-2,2'-dihydroxy-1,1'-dinaphthyl (H(2)(Trip(2)BINO)) or 3,3'-bis(2,6-diisopropylphenyl)-2,2'-dihydroxy-1,1'-dinaphthyl (H(2)(Dip(2)BINO)) in racemic and enantiopure form. The racemic complex [Y(biphen)[N(SiHMe(2))(2)](thf)(2)] dimerizes upon heating to give the heterochiral complex (R,S)-[Y(biphen)[N(SiHMe(2))(2)](thf)](2). The corresponding dimeric heterochiral lanthanum complex was the sole product in the reaction of H(2)(Biphen) with [La[N(SiHMe(2))(2)](3)(thf)(2)]. Single-crystal X-ray diffraction of both dimeric complexes revealed that the two Ln(biphen)[N(SiHMe(2))(2)](thf) fragments are connected through bridging phenolate groups of the biphenolate ligands. The two different phenolate groups undergo an intramolecular exchange process in solution leading to their equivalence on the NMR timescale. All complexes were active catalysts for the hydroamination/cyclization of aminoalkynes and aminoalkenes at elevated temperature, with [Y((R)-dip(2)bino)[N(SiHMe(2))(2)](thf)(2)] being the most active one giving enantioselectivities of up to 57 % ee. Kinetic resolution of 2-aminohex-5-ene proceeded with this catalyst with 6.4:1 trans selectivity to give 2,5-dimethylpyrrolidine with a k(rel) of 2.6.

Unusual ligand coordination for cesium

When complexed by tetrabenzo-24-crown-8, the cesium ion can accommodate unprecedented ligation. The structures of the following complexes are presented. [Cs(tetrabenzo-24-crown-8)(eta 1-NCMe)2(eta 2-NCMe)][NO3] (1): triclinic P1, a = 12.0119(14) A, b = 13.3680(15) A, c = 13.7859(12) A, alpha = 89.124(8) degrees, beta = 66.928(9) degrees, gamma = 71.536(10) degrees, V = 1916.7(4) A3, Z = 2. [Cs(tetrabenzo-24-crown-8)(eta 1-NCMe)2(eta 2-CH2Cl2)][NO3] (2): triclinic, P1, a = 12.295(3) A, b = 13.295(3) A, c = 13.782(3) A, alpha = 89.105(17) degrees, beta = 66.096(18) degrees, gamma = 71.980(19) degrees, V = 1929.5(8) A3, Z = 2. These structures are the first reported examples of linear eta 2-acetonitrile coordination to any metal ion and the first structures illustrating eta 2-acetonitrile and dichloromethane ligation to an alkali metal ion. Possible steric and electronic origins of these unusual metal-ligand interactions are discussed.

Molecular Structures of the Heavier Alkali Metal Salts of Supermesitylphosphane: A Systematic Investigation

The molecular structures of the rubidium and cesium derivatives of supermesitylphosphane [i.e., (2,4,6-(t)Bu(3)C(6)H(2))PH(2) = (t)Bu(3)MesPH(2)] as well as several base adducts of these are reported. Sodium hydride, potassium hydride, rubidium metal, and cesium metal react with (t)Bu(3)MesPH(2) in tetrahydrofuran solution at room temperature to produce MPRH salts 1-4 [M = Na (1), K (2), Rb (3), Cs (4); R = (t)Bu(3)Mes] in good yields. X-ray-quality crystals of 2 and 3 were obtained by slow evaporation of solutions of the corresponding MP(H)(t)Bu(3)Mes species dissolved in toluene/thf. Complex 4 was crystallized from hot toluene. On the other hand, slow evaporation of a toluene/tetrahydrofuran solution of CsP(H)(t)Bu(3)Mes (4) produces crystals of the composition {[CsP(H)(t)Bu(3)Mes](2)(&mgr;-THF)(0.9).toluene}(x)() (5). Crystallization of 4 in the presence of pyridine yields crystals of {[CsP(H)(t)Bu(3)Mes](2)(&mgr;-pyridine)}(x)() (6). Also, crystallization of complexes 3 and 4 from toluene/N-methylimidazole (N-MeIm) gives the isomorphous complexes {[RbP(H)(t)Bu(3)Mes](2)(&mgr;-N-MeIm)}(x)() (7) and {[CsP(H)(t)Bu(3)Mes](2)(&mgr;-N-MeIm)}(x)() (8), respectively. However, crystallization of 4 from toluene in the presence of bidentate or polydentate bases such as dimethoxyethane or pentamethyldiethylenetriamine does not result in incorporation of these bases into the lattice. Instead, the toluene solvate {[CsP(H)(t)Bu(3)Mes](2)(eta(3)-toluene)(0.5)}(x)() (9) is obtained. On the other hand, crystallization of 4 from toluene/ethylenediamine gives the base adduct {[CsP(H)(t)Bu(3)Mes](2)(&mgr;-ethylenediamine)}(x)() (10). Complex 3 crystallizes in the triclinic space group P&onemacr;. Crystal data for 3 at 218 K: a = 6.71320(10) Å, b = 10.5022(2) Å, c = 14.9733(3) Å, alpha = 91.3524(13) degrees, beta = 102.5584(13) degrees, gamma = 107.7966(14) degrees; Z = 1; R(1) = 6.55%. Complex 4 crystallizes in the triclinic space group P&onemacr;. Crystal data for 4 at 223 K: a = 7.0730(14) Å; b = 10.395(2) Å; c = 14.933(2) Å; alpha = 81.97(1) degrees; beta = 76.35(2) degrees; gamma = 71.824(14) degrees; Z = 1; R(1) = 4.56%. Complex 5 crystallizes in the monoclinic space group P2(1)/c. Crystal data for 5 at 243 K: a = 15.039(2) Å; b = 16.152(3) Å; c = 20.967(5) Å; beta = 91.53(2) degrees; Z = 4; R(1) = 4.83%. Complex 6 crystallizes in the orthorhombic space group Pbcn. Crystal data for 6 at 298 K: a = 14.686(2) Å; b = 21.295(5) Å; c = 28.767(5) Å; Z = 8; R(1) = 5.61%. Complex 7 crystallizes in the orthorhombic space group Pbcn. Crystal data for 7 at 218 K: a = 14.5533(2) Å; b = 21.4258(5) Å; c = 28.5990(5) Å; Z = 8; R(1) = 4.61%. Complex 8 crystallizes in the orthorhombic space group Pbcn. Crystal data for 8 at 219 K: a = 14.6162(2) Å; b = 21.3992(3) Å; c = 28.7037(2) Å; Z = 8; R(1) = 3.57%. Complex 9 crystallizes in the triclinic space group P&onemacr;. Crystal data for 9 at 293 K: a = 11.147(4) Å; b = 14.615(4) Å; c = 14.806(5) Å; alpha = 70.57(3) degrees; beta = 71.85(3) degrees; gamma = 72.93(2) degrees; Z = 2; R(1) = 5.13%. Complex 10 crystallizes in the triclinic space group P&onemacr;. Crystal data for 10 at 173 K: a = 10.5690(4) Å; b = 15.0376(5) Å; c = 15.3643(5) Å; alpha = 111.8630(10) degrees; beta = 100.4120(10) degrees; gamma = 97.4820(2) degrees; Z = 2; R(1) = 4.87%. A common feature of the molecular structures of complexes 2-10 is an infinitely extended polymeric ladder framework in the solid state. Both solution and solid-state NMR data are presented.