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J G Brennan

Publications and source records attributed to J G Brennan.

5 recordsLinked to original sources
PubMed2001

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)().

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PubMed2001

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.

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PubMed2000

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

Crystalline coordination complexes of Sm(EPh)2 (E = Se, Te) are described. The selenolate compound Sm(SePh)2 is unstable in solution, but a divalent selenolate can be prepared and isolated when precisely 1 equiv of Zn(SePh)2 is present to form heterometallic [(THF)3Sm(mu 2-SePh)3Zn(mu 2-SePh)]n (1). This compound is a 1D coordination polymer with alternating Sm(II) and Zn(II) ions connected by an alternating (1,3) number of bridging selenolate ligands and three THF ligands bound to each Sm(II) ion. The tellurolate Sm(TePh)2 forms a stable pyridine coordination compound (py)5Sm(TePh)2 (2) that is isostructural with known Eu and Yb benzenetellurolates. Both compounds were characterized by conventional spectroscopic methods. Polymer 1 was characterized by low-temperature single-crystal X-ray diffraction, and the unit cell of the tellurolate was determined. Crystal data (Mo K alpha, 153(5) (K) are as follows. 1: monoclinic space group P21, a = 10.666(2) A, b = 16.270(3) A, c = 12.002(3) A, beta = 114.81(2) degrees, Z = 2.2: orthorhombic space group Pbca, with a = 13.865(3) A, b = 16.453(5) A, c = 31.952(7) A, Z = 8.

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