Synthesis of Polynuclear Complexes with an Amino Acid or a Peptide as a Bridging Ligand

Reactions of calcium bromide with enantiopure and racemic proline in aqueous solution lead to two solids in which the zwitterionic amino acid acts as a bridging ligand between neighbouring cations. Depending on the chirality of the amino acid, topologically very different products are obtained. With racemic proline, bromide acts as a simple uncoordinated counter-anion for the cationic heterochiral chains incatena-poly[[aquacalcium(II)]-μ-aqua-μ3-DL-proline-μ2-DL-proline], {[Ca(C5H9NO2)2(H2O)2]Br2}n. In agreement with chemical intuition, only carboxylate and aqua O atoms coordinate the alkaline earth cation in a low-symmetry arrangement. In contrast, L-proline affords the two-dimensional network poly[dibromidobis(μ2-L-proline)calcium(II)], [CaBr2(C5H9NO2)2]n, with an unexpected CaBr2unit in a more regular coordination sphere.

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Amino acid complexes of platinum(IV). V. A dimethylplatinum(IV) complex containing deprotonated glycinate as an amido-bridging ligand, [PtMe2(OH)(μ-NHCH2CO2)]2−2

Inorganica Chimica Acta ◽

10.1016/s0020-1693(00)83733-0 ◽

1981 ◽

Vol 50 ◽

pp. 137-140 ◽

Cited By ~ 11

Author(s):

Neville H. Agnew ◽

Trevor G. Appleton ◽

John R. Hall

Keyword(s):

Amino Acid ◽

Amino Acid Complexes ◽

Bridging Ligand

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Mehrkernige Oxo-Vanadium- und Oxo-Molybdän-Komplexe mit dem Dianion der Quadratsäure als Brückenligand. Strukturen von [C(NH2)3]4[V2O2F4(C4O4)2]·4H2O, [nBu4N]4[V3O3F4(C4O4)3]·2H2O, [Et4N]3[Mo3O8F(C4O4)2], [Et4N]4[Mo4O10F6(C4O4)] und [ Et4N]3[Mo2O3Cl3(C4O4)2] / Polynuclear Complexes of Oxo-Vanadium and Oxo-Molybdenum with the Dianion of Squaric Acid as Bridging Ligand. Crystal Structures of [C(NH2)3]4[V2O2F4(C4O4)2]·4H2O, [nBu4N]4[V3O3F4(C4O4)3]·2H2O, [Et4N]3[Mo3O8F(C4O4)2], [Et4N]4[Mo4O10F6(C4O4)] and [ Et4N]3[Mo2O3Cl3(C4O4)2]

Zeitschrift für Naturforschung B ◽

10.1515/znb-1996-0113 ◽

1996 ◽

Vol 51 (1) ◽

pp. 57-67 ◽

Cited By ~ 17

Author(s):

Martin Hilbers ◽

Margita Meiwald ◽

Rainer Mattes

Keyword(s):

Squaric Acid ◽

Polynuclear Complexes ◽

X Ray Diffraction ◽

Fluoride Ions ◽

Metal Centers ◽

X Ray ◽

Bridging Ligand ◽

Metal Atoms ◽

Central Defect ◽

Oxo Ligand

Abstract Aqueous or methanolic solutions containing vanadium(IV), molybdenum(V) and molyb-denum(VI) oxo species and fluoride ions react with squaric acid to give the oligonuclear complexes [C(NH2)3]4[V2O2F4(C4O4)2]·4H2O (1), Cs4[V3O3F4(C4O4)3]·5H2O (2a), [nBu4N]4[V3O3F4(C4O4)3]·2H2O (2b), [Et4N]4[Mo4O10F6(C4O4)] (3a), [Et4N]4[Mo4O10Cl6(C4O4)] (3b), [Et4N]3[Mo3O8F(C4O4)2] (4) and [Et4N]3[Mo2O3Cl3(C4O4)2] (5). The structures of compounds 1, 2a, 2b, 3a, 4 and 5 have been determined by single crystal X-ray diffraction. The [V2O2F4(C4O4)2]4- ion in 1 consists of the planar V2O2F4 core with the vanadium sites bridged by two ,μ-1,2-squarato ligands. The unique cone-shaped [V3O3F4(C4O4)3]4- ion in 2a and 2b contains a central defect and severely distorted V3F4 cubane unit. Each vanadium atom bears a terminal oxo ligand; pairs of vanadium atoms are bridged by μ-1,2-squarato ligands. The [Mo4O10F6(C4O4)]4- ion in 3a consists of a squarate ion, which is coordinated to four metal centers. Pairs of metal atoms are bridged by μ(O)μ(F)-bridges. Two terminal oxo ligands and one terminal fluoro ligand complete the metal coordination. Oxo and fluoro ligands are partly disordered. The structure of the [Mo3O8F(C4O4)2]3- ion in 4 is related to the structure of [V3O3F4(C4O4)3]4- It consists of a defect Mo3(O3F) cubane unit. Two pairs of molybdenum atoms are bridged by μ-1,2-squarato ligands. Terminal oxo and dioxo groups complete the molybdenum coordination. The [Mo2O3Cl3(C4O4)2]3- ion in 5 exhibits a unique structure with a planar OClMo(μ-O)(μ-Cl)MoOCl core and a cis, cis-orientation of the oxygen ligands. Two, μ-1,2-squarato ligands bridge the molybdenum centers above and below the Mo2O3Cl3 plane.

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