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]

Abstract

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(NH 2 ) 3 ] 4 [V 2 O 2 F 4 (C 4 O 4 ) 2 ]·4H 2 O (1), Cs 4 [V 3 O 3 F 4 (C 4 O 4 ) 3 ]·5H 2 O (2a), [ n Bu 4 N] 4 [V 3 O 3 F 4 (C 4 O 4 ) 3 ]·2H 2 O (2b), [Et 4 N] 4 [Mo 4 O 10 F 6 (C 4 O 4 )] (3a), [Et 4 N] 4 [Mo 4 O 10 Cl 6 (C 4 O 4 )] (3b), [Et 4 N] 3 [Mo 3 O 8 F(C 4 O 4 ) 2 ] (4) and [Et 4 N] 3 [Mo 2 O 3 Cl 3 (C 4 O 4 ) 2 ] (5). The structures of compounds 1, 2a, 2b, 3a, 4 and 5 have been determined by single crystal X-ray diffraction. The [V 2 O 2 F 4 (C 4 O 4 ) 2 ] 4- ion in 1 consists of the planar V 2 O 2 F 4 core with the vanadium sites bridged by two ,μ-1,2-squarato ligands. The unique cone-shaped [V 3 O 3 F 4 (C 4 O 4 ) 3 ] 4- ion in 2a and 2b contains a central defect and severely distorted V 3 F 4 cubane unit. Each vanadium atom bears a terminal oxo ligand; pairs of vanadium atoms are bridged by μ-1,2-squarato ligands. The [Mo 4 O 10 F 6 (C 4 O 4 )] 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 [Mo 3 O 8 F(C 4 O 4 ) 2 ] 3- ion in 4 is related to the structure of [V 3 O 3 F 4 (C 4 O 4 ) 3 ] 4- It consists of a defect Mo 3 (O 3 F) 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 [Mo 2 O 3 Cl 3 (C 4 O 4 ) 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 Mo 2 O 3 Cl 3 plane.