Divalent samarium compounds with heavier chalcogenolate (EPh; E = Se, Te) ligands

Divalent and trivalent gas-phase coordination complexes of californium: evaluating the stability of Cf(ii)

The divalent oxidation state is increasingly stable relative to the trivalent state for the later actinide elements, with californium the first actinide to exhibit divalent chemistry under moderate conditions. Although there is evidence for divalent Cf in solution and solid compounds, there are no reports of discrete complexes in which Cf(II) is coordinated by anionic ligands. Described here is the divalent Cf methanesulfinate coordination complex, Cf(II)(CH3SO2)3(-), prepared in the gas phase by reductive elimination of CH3SO2 from Cf(III)(CH3SO2)4(-). Comparison with synthesis of the corresponding Sm and Cm complexes reveals reduction of Cf(III) and Sm(III), and no evidence for reduction of Cm(III). This reflects the comparative 3+/2+ reduction potentials: Cf(3+) (-1.60 V) ≈ Sm(3+) (-1.55 V) ≫ Cm(3+) (-3.7 V). Association of O2 to the divalent complexes is attributed to formation of superoxides, with recovery of the trivalent oxidation state. The new gas-phase chemistry of californium, now the heaviest element to have been studied in this manner, provides evidence for Cf(II) coordination complexes and similar chemistry of Cf and Sm.

Three-Dimensional 3d−4f Polymers Containing Heterometallic Rings: Syntheses, Structures, and Magnetic Properties

Two novel three-dimensional (3D) 3d-4f mixed complexes [Ln(H(2)O)(4)][Ni(2)TTHA(SCN)(2)].H(3)O+ [Ln = Pr (1), Ce (2); H(6)TTHA = triethylenetetraaminehexaacetic acid], based on the building blocks of [Ni(2)TTHA(SCN)(2)](4-), were synthesized and characterized by X-ray crystal diffraction and magnetic properties. The single-crystal structures show that these complexes form a 3D framework, comprised of an unusual infinite one-dimensional chain based on heterometallic Ln2Ni2 rings. The temperature-dependent magnetic susceptibilities were analyzed by an approximate model, leading to g = 2.06. Delta = 2.83, zJ' = -0.6 cm-1 for complex 1 and g = 2.07, Delta = 1.00, zJ' = -0.5 cm(-1) for complex 2.

Three-Dimensional 3d−4f Heterometallic Coordination Polymers: Synthesis, Structures, and Magnetic Properties

Three new 3d-4f heterometallic coordination polymers, [Ln(2)(H(2)O)(4)M(2)(H(2)O)(2)(QA)(5)].nH(2)O (H(2)QA = quinolinic acid; Ln = Gd, M = Ni, n = 7 (1); Ln = Gd, M = Co, n = 6.5 (2); Ln = Dy, M = Co, n = 6.5 (3)), have been synthesized through hydrothermal pretreatment and cooling-down crystallization. These compounds possess the isostructural 3D frameworks with 1D chairlike channels along the c axis, which are occupied by noncoordinating water molecules. Crystal data: for 1, C(35)H(41)Gd(2)Ni(2)N(5)O(33), orthorhombic, space group Pna2(1), with a = 28.567(6) A, b = 14.498(3) A, c = 12.250(2) A, and Z = 4; for 2, C(35)H(40)Gd(2)Co(2)N(5)O(32.5), orthorhombic, space group Pna2(1), with a = 28.843(3) A, b = 14.4325(13) A, c = 12.2275(9) A, and Z = 4; for 3, C(35)H(40)Dy(2)Co(2)N(5)O(32.5), orthorhombic, space group Pna2(1), with a = 28.8471(14) A, b = 14.4534(10) A, c = 12.2520(7) A, and Z = 4. The magnetic behaviors for the three compounds have been investigated.

Lanthanide−Transition Metal Chalcogenido Cluster Materials

[(THF)3Sm(SePh)2Zn(SePh)2]n decomposes to give a variety of products, including [(THF)8Sm4Se(SePh)8](2+)[Zn8Se(SePh)16](2-), an ionic cluster that can also be prepared in more than 60% yield by stoichiometric addition of Se to a mixture of Sm(SePh)3 and Zn(SePh)2. The isostructural Nd compound [(THF)8Nd4Se(SePh)8](2+)[Zn8Se(SePh)16](2-) was also prepared by the stoichiometric route to establish the viability of this cluster type with redox-inactive Ln. In addition, the salt [Yb(THF)6](3+)[Fe4Se4(SePh)4](3-) was isolated and structurally characterized. These ionic cluster materials illustrate the difficulties associated with doping Ln ions into covalent metal chalcogenido matrixes.

Chalcogen rich lanthanide clusters from halide starting materials (II): selenido compounds

Lanthanides reduce mixtures of I(2) and PhSeSePh in THF, and the resultant heteroligand mixture reacts further with elemental Se in pyridine to give (THF)(6)Ln(4)I(2)(SeSe)(4)(mu(4)-Se).THF (Ln = Tm, Ho, Er, Yb). These selenium rich clusters contain a square array of Ln(III) ions connected through a single (mu(4)-Se) ligand. There are two I(-) ligands coordinating nonadjacent Ln(III) ions on the side of the cluster opposite the (mu(4)-Se), and the edges of the square are bridged by mu(2)-SeSe groups. The electronic spectrum of the Yb compound contains two absorption maxima that can tentatively be assigned as Se(2-) to Yb and SeSe to Yb charge-transfer absorptions, by comparison with the featureless absorption spectra of the Tm, Ho, and Er derivatives. With a 1/1/1/1 Yb/I/Ph(2)S(2)/Se stoichiometry, chalcogen rich compounds are not obtained, but instead, in Yb chemistry, the selenido cluster (THF)(10)Yb(6)Se(6)I(6) can be isolated in 51% yield. The molecular structure of this compound contains a Yb(4)Se(4) cubane fragment, with an additional Yb(2)Se(2) layer capping one face of the cube. Each Yb coordinates a terminal I(-). This intensely colored compound also has an absorption maximum in the visible spectrum. Upon thermolysis, the selenium rich compounds give Ln(2)Se(3) that is free of iodide contamination.

Chalcogen-rich lanthanide clusters: cluster reactivity and the influence of ancillary ligands on structure

Ytterbium metal reacts with PhEEPh (E = S, Se, Te) and elemental Se in pyridine to give (pyridine)(8)Yb(4)(SeSe)(2)(Se)(2)(mu(2)-SPh)(2)(SPh)(2), (py)(8)Yb(4)Se(SeSe)(3)(SeSeSePh)(Se(0.38)SePh), and (py)(8)Yb(4)Se(SeSe)(3)(SeSeTePh)(SeTePh), respectively. The SePh and TePh compounds contain a square array of Ln(III) ions all connected to a central Se(2)(-) ligand. Three edges of the square are bridged by diselenide ligands, with the fourth SeSe unit coordinating to an EPh ligand that has been displaced from an inner Yb coordination sphere. Differences in the two compounds have their origin in the relative strength of the Yb-E(Ph) bond. In the TePh compound, there is a complete insertion of Se into the remaining Yb-Te(Ph) bond to give a terminal SeTePh ligand, while in the SePh compound there is a compositional disorder in the structure comprised of a terminal SePh ligand and a minor component that has Se inserted into the Yb-Se(Ph) bond to give a terminal SeSePh ligand. The thiolate compound differs dramatically, crystallizing as a rhombohedral array of four Yb(III) ions connected by a pair of mu(3)-Se(2)(-) ligands, with the edges of the rhombus spanned by alternating diselenide and SPh. The SPh coordinate directly to Yb(III) ions in terminal or bridging modes. Cluster interconversion is facile: (py)(4)Yb(SePh)(2) reduces (py)(8)Yb(4)Se(SeSe)(3)(SeSeSePh)(Se(0.38)SePh) to give the cubane cluster [(py)(2)YbSe(SePh)](4), and the cubane reacts with elemental Se to give (py)(8)Yb(4)Se(SeSe)(3)(SeSeSePh)(Se(0.38)SePh). Upon thermolysis, these compounds give YbSe(x)().

Preparations, structures, and magnetic properties of a series of novel copper(II)-lanthanide(III) coordination polymers via hydrothermal reaction

The hydrothermal reaction of Ln2O3 (Ln = Er, Gd, and Sm), pyridine-2,5-dicarboxylic acid (H2pydc), and Cu(II) reagents (CuO, Cu(OAc)2-2H2O, or CuCl2-2H2O) with a mole ratio of 1:2:4 resulted in the formation of six polymeric Cu(II)-Ln(III) complexes, [(Ln2Cu3(pydc)6(H2O)12)-4H2O]n (Ln = Er (1); Ln = Gd (2)), [(Ln4Cu2(pydc)8(H2O)12)-4H2O]n (Ln = Sm (3); Ln = Gd (4); Ln = Er (5)), and [(Gd2Cu2(pydc)4(H2O)8)-Cu(pydc)2-12H2O]n (6). 1 and 2 are isomorphous and crystallize in triclinic space group Ponebar. Compounds 3-5 are isomorphous and crystallize in monoclinic space group P2(1)/c. Compound 6 crystallizes in triclinic space group Ponebar. Complexes 1 and 2 have one-dimensional zigzag chain structures and compounds 3-5 display three-dimensional wavelike polymeric structures, while 6 has an infinite sandwich-type structure. The different structures of the complexes are induced by the different forms of Cu(II) reagents; the reactions of Cu(OAc)2-2H2O yield high Cu/Ln ratio products 1, 2, and 6, while the reactions of CuO or CuCl2-2H2O/2,2'-bipyridine results in low Cu/Ln ratio compounds 3-5. Temperature-dependent magnetic susceptibilities for 2, 4, and 5 were studied, and the thermal stabilities of complexes 2 and 4 were examined.

Heteroleptic lanthanide compounds with chalcogenolate ligands: reduction of PhNNPh/PhEEPh (E = Se or Te) mixtures with Ln (Ln = Ho, Er, Tm, Yb). Thermolysis can give LnN or LnE

Lanthanide metals reduce mixtures of azobenzene and PhEEPh (E = Se or Te) in pyridine to give the bimetallic compounds [(py)2Ln(EPh)(PhNNPh)]2 (E = Se, Ln = Ho (1), Er (2), Tm (3), Yb (4); E = Te, Ln = Ho (5), Er (6), Tm (7), Yb (8)). The structures of [(py)2Er(mu-eta 2-eta 2-PhNNPh)(SePh)](2).2py (2) and [(py)2Ho(mu-eta 2-eta 2-PhNNPh)(TePh)](2).2py (5) have been determined by low-temperature single-crystal X-ray diffraction, and the nearly identical unit cell volumes of the remaining compounds indicate they are most likely isomorphous to 2 or 5. In all compounds, the Ln(III) ions are bridged by a pair of mu-eta 2-eta 2-PhNNPh ligands that, from the N-N bond length, have clearly been reduced to dianions. Charge is balanced by the single terminal EPh ligand on each Ln, and the coordination sphere is saturated by two pyridine donors to give seven coordinate metal centers. Thermal decomposition of 5 gives HoTe, 8 gives a mixture of YbN and YbTe, and 1 does not give a crystalline solid-state product. Crystal data (Mo K alpha, 153(2) K) are as follows: 2, monoclinic group P2(1)/n, a = 11.864(3) A, b = 14.188(2) A, c = 17.624(2) A, beta = 91.62(2) degrees, V = 2965(1) A3, Z = 4; 5, triclinic space group P1, a = 10.349(2) A, b = 17.662(4) A, c = 17.730(8) A, alpha = 75.82(3) degrees, beta = 74.11(3) degrees, gamma = 89.45(2) degrees, V = 3016(2) A3, Z = 2.