Synthesis and structural characterizations of four polyoxometalate compounds consisting of transition metals or alkaline cations as the bridging units

Polyoxometalate Insertion into Cu–pz Porous and Cu-bim Knighthead Coordination Polymers: [{Cu4(pz)5.5}{Cu2(2,2'-bim)3}0.5{P2W18O62}]·H2O

The structure of crystallised {[Cu4(pz)5.5][Cu2(2,2′-bim)3]0.5[P2W18O62]}·H2O (1) (pz = pyrazine, bim = biimidazole) is reported. The crystal structure is characterised by cage-like pores [Cu8(pz)11]8+ of Cu ions linked through pz ligands. [P2W18O62]6– polyanions are capsulated into cage-like pores of [Cu8(pz)11]8+, forming ‘hamburger’-like units. Furthermore, the three-dimensional framework in 1 is achieved via copper-pyrazolate layers, binuclear copper-biimidazole subunits, and Dawson-type polyoxometalate clusters. The electrochemical properties of compound 1 were also studied in detail.

Tris(2,2'-bipyridine)-nickel(II) hexa-molybdate

The asymmetric unit of the title compound, [Ni(C₁₀H₈N₂)₃][Mo₆O₁₉], consists of one complex [(Ni(C₁₀H₈N₂)₃]²⁺ cation and one Lindqvist-type [Mo₆O₁₉]²⁻ polyanion. The Ni²⁺ ion is in a distorted octa­hedral coordination by six N atoms from three chelating 2,2′-bipyridine ligands. The Lindqvist-type anion exhibits the characteristic Mo—O bond-length distribution, with the shortest bonds being the Mo—O(terminal) bonds [mean = 1.679 (2) Å] and the longest being those to the central O atom [mean = 2.318 (7) Å]. A number of C—H⋯O inter­actions contribute to the crystal packing.

(μ-Oxalato-κO,O:O,O)bis-[bis-(2,2'-bipyridine-κN,N')cobalt(II)] μ(6)-oxido-dodeca-μ(2)-oxido-hexa-oxido-hexa-tungstate(VI)

The asymmetric unit of the title compound, [Co(2)(C(2)O(4))(C(10)H(8)N(2))(4)][W(6)O(19)], consists of one half of the complex [Co(2)(C(2)O(4))(C(10)H(8)N(2))(4)](2+) cation and one half of the Lindqvist-type [W(6)O(19)](2-) isopolyanion. Both constituents are completed by crystallographic inversion symmetry. In the dimeric cation, the Co(II) atom is surrounded in a distorted octa-hedral coordination by four N atoms from two chelating 2,2'-bipyridine ligands and by two O atoms from the chelating oxalate anion. The Lindqvist-type anion exhibits the characteristic W-O bond-length distribution, with the shortest bonds being the W-O(terminal) bonds and the longest being those to the central O atom.

Tris(2,2'-bipyridine)-cobalt(II) μ(6)-oxido-dodeca-μ(2)-oxido-hexa-oxidohexa-molydate(VI)

In the title compound, [Co(C(10)H(8)N(2))(3)][Mo(6)O(19)], the Co(2+) cation is surrounded in a distorted octa-hedral coordination by six N atoms from three 2,2'-bipyridine ligands. The distribution of Mo-O bond lengths in the Lindqvist isopolyanion is consistent with other structures containing the same unit. In the crystal, the cations and anions are linked by C-H⋯O inter-actions.

Redetermination of hexa-sodium hepta-molybdate(VI) 14-hydrate

The structure of the title compound, Na₆(Mo₇O₂₄)·14H₂O, has been redetermined [Sjöbom & Hedman (1973). Acta Chem. Scand.27, 3673–3674] and the hydrogen atoms have been located. The Na⁺ cations adopt distorted octa­hedral geometries and the structure of the [Mo₇O₂₄]⁶⁻ anion is consistent with those of other hepta­molbydates. In the crystal, numerous O—H⋯O hydrogen bonds help to establish the packing.

Tetra-kis(2-methyl-benzimidazolium) β-octa-molybdate(VI)

The asymmetric unit of the title compound, (C₈H₉N₂)₄[Mo₈O₂₆], consists of two 2-methyl­benzimidazolium cations and one-half of a β-Mo₈O₂₆⁴⁻ anion, which is completed by crystallographic inversion symmetry. An extensive net of N—H⋯O hydrogen bonds between the cations and anions contribute to the crystal packing.

Bis{tris-[3-(2-pyrid-yl)-1H-pyrazole]nickel(II)} dodeca-molybdo(V,VI)phosphate hexa-hydrate

The hydro­thermally prepared title compound, [Ni(C₈H₇N₃)₃]₂[PMo₁₂O₄₀]·6H₂O, is a member of the isotypic series [(M(C₈H₇N₃)₃]₂[PMo₁₂O₄₀]·6H₂O where M is Mn, Cd, and Fe. The Ni²⁺ cation is in a distorted octa­hedral environment, coordinated by six N atoms from three chelating 3-(2-pyrid­yl)-1H-pyrazole ligands. In the one-electron reduced heteropolyanion, two O atoms of the central PO₄ group ( symmetry) are equally disordered about an inversion centre. N—H⋯O and O—H⋯O hydrogen bonds contribute to the crystal packing. Compared with the isotypic structures, the main difference is related with the M—N bond lengths, whereas all other bond lengths, angles and the hydrogen-bonding motifs are very similar.

Bis{tris[3-(2-pyridyl)pyrazole]manganese(II)} dodecamolybdosilicate hexahydrate

The title compound, [Mn(C₈H₇N₃)₃]₂[SiMo₁₂O₄₀]·6H₂O, consists of an [SiMo₁₂O₄₀]⁴⁻ heteropolyanion, lying on a centre of inversion, and a complex [Mn(C₈H₇N₃)₃]⁴⁺ cation. The Mn^II atom of the cation is hexa­coordinated in a distorted octa­hedral geometry by six N atoms from three chelating 3-(2-pyrid­yl)pyrazole ligands. In the heteropolyanion, the four O atoms of the tetra­hedral SiO₄ group each half-occupy eight sites due to Si lying on the centre of inversion. N—H⋯O and O—H⋯O hydrogen bonding mediated by the water mol­ecules leads to a consolidation of the structure.

Bis{tris-[3-(2-pyrid-yl)-1H-pyrazole]iron(II)} dodeca-molybdo(V,VI)phosphate hexa-hydrate

Crystals of the title compound, [Fe(C₈H₇N₃)₃]₂[PMo₁₂O₄₀]·6H₂O, prepared under hydro­thermal conditions, are isotypic with the Mn²⁺ and Cd²⁺ analogues. The Fe²⁺ cation is in a distorted octa­hedral coordination by six N atoms from three chelating 3-(2-pyrid­yl)-1H-pyrazole ligands. The heteropoly­anion [PMo₁₂O₄₀]⁴⁻ is a one-electron reduced species in which two O atoms of the central PO₄ group ( symmetry) are equally disordered about an inversion centre. N—H⋯O and O—H⋯O hydrogen bonds make a contribution to the crystal packing. The Fe—N bond lengths [2.085 (19)—2.15 (2) Å] are somewhat shorter than the Mn—N and Cd—N bond lengths [2.224 (6)–2.283 (5) and 2.316 (7)–2.334 (6) Å, respectively]. All other bond lengths and angles and the hydrogen-bonding motifs are very similar in the isotypic structures.

Bis{tris-[3-(2-pyrid-yl)-1H-pyrazole]cadmium(II)} dodeca-molybdo(V,VI)phosphate hexa-hydrate

The hydro­thermally prepared title compound, [Cd(C₈H₇N₃)₃]₂[PMo₁₂O₄₀]·6H₂O, is isotypic with its Mn^II analogue [Hao et al. (2010 ▶). Acta Cryst. E66, m231–m232]. The Cd^II cation is in a distorted octa­hedral environment, coordinated by six N atoms from three chelating 3-(2-pyrid­yl)-1H-pyrazole ligands. In the reduced heteropolyanion, two O atoms of the central PO₄ group ( symmetry) are equally disordered about an inversion centre. N—H⋯O and O—H⋯O hydrogen bonds contribute to the crystal packing. Compared with the Mn^II analogue, the Cd—N bond lengths are longer at 2.316 (7)–2.334 (6) Å, versus 2.224 (6)–2.283 (5) Å for Mn—N, whereas all other bond lengths and angles and the hydrogen-bonding motifs are very similar in the two structures.

Bis{tris-[3-(2-pyrid-yl)-1H-pyrazole]manganese(II)} dodeca-molybdo(V,VI)phosphate hexa-hydrate

The asymmetric unit of the title compound, [Mn(C₈H₇N₃)₃]₂[PMo₁₂O₄₀]·6H₂O, consists of a complex [Mn(C₈H₇N₃)₃]²⁺ cation, half of a mixed-valent Mo^V,VI α-Keggin-type [PMo₁₂O₄₀]⁴⁻ heteropolyanion, and three uncoordinated water mol­ecules. The Mn²⁺ cation is surrounded by six N atoms from three chelating 3-(2-pyrid­yl)-1H-pyrazole ligands in a distorted octa­hedral coordination. In the heteropolyanion, two O atoms of the central PO₄ group ( symmetry) are equally disordered about an inversion centre. N—H⋯O and O—H⋯O hydrogen bonding between the cations, anions and the uncoordinated water mol­ecules leads to a consolidation of the structure.

Bis{tris-[3-(2-pyrid-yl)-1H-pyrazole]iron(II)} tetra-deca-molybdo(V,VI)silicate

The asymmetric unit of the title compound, [Fe(C₈H₇N₃)₃]₂[SiMo₁₄O₄₄], consists of a complex [Fe(C₈H₇N₃)₃]²⁺ cation and half of a derivative of an α-Keggin-type anion, [SiMo₁₄O₄₄]⁴⁻. In the mixed-valent Mo^V/VI anion, the α-Keggin type core is capped on two oppositely disposed tetra­gonal faces by additional (MoO₂) units. The [SiMo₁₄O₄₄]⁴⁻ anion shows disorder. Two O atoms of the central SiO₄ group ( symmetry) are equally disordered about an inversion centre. Moreover, two of the outer bridging O atoms and the O atoms of the capping (MoO₂) unit are likewise disordered. The Fe²⁺ cation is surrounded in a slightly distorted octa­hedral coordination by six N atoms from three 3-(2-pyrid­yl)-1H-pyrazole ligands. N—H⋯O hydrogen bonding between the cations and anions leads to a consolidation of the structure.

Tris{aqua-bis[3-(2-pyrid-yl)-1H-pyrazole]copper(II)} di-μ(9)-arsenato-hexa-triaconta-μ(2)-oxido-octa-deca-oxidoocta-deca-molybdate(VI)

The title compound, [Cu(C(8)H(7)N(3))(2)(H(2)O)](3)[As(2)Mo(18)O(62)], consists of two subunits, viz. an α-Dawson-type [As(2)Mo(18)O(62)](6-) anion and a complex [Cu(C(8)H(7)N(3))(2)(H(2)O)](2+) cation. The copper(II) ion (site symmetry .2) is penta-coordinated in a distorted square-pyramidal manner by four N atoms from two chelating 3-(2-pyrid-yl)pyrazole ligands in equatorial positions and one water mol-ecule in the apical position. In the heteropolyanion, two O atoms of the AsO(4) group (3. symmetry) are equally disordered about the threefold rotation axis. N-H⋯O and O-H⋯O hydrogen bonding between the neutral mol-ecules and the water mol-ecules leads to a consolidation of the structure.

Bis{tris-[3-(2-pyrid-yl)-1H-pyrazole]nickel(II)} dodeca-molybdosilicate tetra-hydrate

The asymmetric unit of the title compound, [Ni(C₈H₇N₃)₃]₂[SiMo₁₂O₄₀]·4H₂O, consists of a complex [Ni(C₈H₇N₃)₃]²⁺ cation, half of a Keggin-type heteropolyanion [SiMo₁₂O₄₀]⁴⁻ and two uncoordinated water mol­ecules. The Ni²⁺ cation is surrounded in a slightly distorted octa­hedral coordination by six N atoms from three chelating 3-(2-pyrid­yl)-1H-pyrazole ligands. In the heteropolyanion, two O atoms of the central SiO₄ group ( symmetry) are equally disordered about an inversion centre. N—H⋯O and O—H⋯O hydrogen bonding between the cations, anions and the uncoordinated water mol­ecules leads to a consolidation of the structure.

Bis{tris-[3-(2-pyrid-yl)-1H-pyrazole]zinc(II)} dodeca-molybdosilicate hexa-hydrate

The asymmetric unit of the title compound, [Zn(C(8)H(7)N(3))(3)](2)[SiMo(12)O(40)]·6H(2)O, consists of a complex [Zn(C(8)H(7)N(3))(3)](2+) cation, half of a Keggin-type [SiMo(12)O(40)](4-) heteropolyanion and three uncoordinated water mol-ecules. The Zn(2+) cation is surrounded in a distorted octa-hedral coordination by six N atoms from three chelating 3-(2-pyrid-yl)pyrazole ligands. In the heteropolyanion, two O atoms of the central SiO(4) group ( symmetry) are equally disordered about an inversion centre. N-H⋯O hydrogen bonding between the cations, anions and the uncoordinated water mol-ecules leads to a consolidation of the structure.

Diaqua-1κO,2κO-(2,2'-bi-1H-imidazole-1κN,N)(oxalato-2κO,O)di-μ-oxido-κO:O-dioxido-1κO,2κO-dimolyb-denum(V) trihydrate

In the title compound, [Mo₂(C₂O₄)O₄(C₆H₆N₄)(H₂O)₂]·3H₂O, the coordination polyhedra for both Mo(V) atoms consist of two bridging O atoms, two atoms of the chelating ligand (oxalate or diimidazole), a terminal O atom and one H₂O mol­ecule. The two distorted octa­hedrally coordinated Mo(V) atoms are linked together via O—O edge-sharing and Mo—Mo inter­actions with a Mo—Mo bond length of 2.564 (5) Å. Uncoordinated water mol­ecules are situated in the voids of the crystal structure. N—H⋯O and O—H⋯O hydrogen bonding between the neutral mol­ecules and the water mol­ecules lead to a consolidation of the structure.