A one‐dimensional coordination polymer with a capped [Cu4O4] cubane core assembled from 2‐(hydroxymethyl)pyridine

The one‐dimensional coordination polymer catena‐poly[[[di‐μ₂‐acetato‐tetrakis[μ₃‐(pyridin‐2‐yl)methanolato]tetracopper(II)]‐di‐μ₂‐diacetamidato] acetonitrile monosolvate], {[Cu₄(C₆H₆NO)₄(CH₃COO)₂(C₂N₃)₂]·CH₃CN}_n, has been prepared from the direct reaction of 2‐(hydroxymethyl)pyridine with Cu(OAc)₂·H₂O (OAc⁻ is acetate) in a methanol–acetonitrile mixture. The four Cu centres are bridged by four O atoms from discrete (pyridin‐2‐yl)methanolate ligands and two acetate groups, forming a capped [Cu₄O₄] cubane core. Each core is doubly bridged to each of two adjacent cores by [N(CN)₂]⁻ anions, resulting in one‐dimensional chains. The magnetic properties of the complex were also studied.     

Na6(H2O)20(V10O28)·4H2O,a novel polyvanadate(V) with a three‐dimensional framework

The novel title polyvanadate(V), poly[[octa‐μ‐aqua‐dodecaaqua‐μ₄‐octacosaoxidodecavanadato‐hexasodium] tetrahydrate], [Na₆(H₂O)₂₀(V₁₀O₂₈)·4H₂O]_n, contains [V₁₀O₂₈]⁶⁻ anions which lie about inversion centres and have approximate 2/m symmetry and which are linked to [Na₃(H₂O)₁₀]³⁺ cations through two terminal and two μ₂‐bridging O atoms. The structure contains three inequivalent Na⁺ cations, two of which form [Na₂(H₂O)₈]_n chains, which are linked via NaO₆ octahedra involving the third Na⁺ ion, thus forming a three‐dimensional framework.     

Two related lithium calixarene complexes, [p‐tert‐butylcalix[4]arene(OMe)(OH)2(OLi)]2·4MeCN and {p‐tert‐butylcalix[4]arene(OH)2(OLi)[OLi(NCMe)2]}2·8MeCN,determined using synchrotron radiation

The crystal structures of acetonitrile solvates of two related lithium calixarene complexes have been determined by low‐temperature single‐crystal X‐ray diffraction using synchrotron radiation. Bis(μ‐5,11,17,23‐tetra‐tert‐butyl‐26,28‐dihydroxy‐25‐methoxy‐27‐oxidocalix[4]arene)dilithium(I) acetonitrile tetrasolvate, [Li₂(C₄₅H₅₇O₄)₂]·4C₂H₃N or [p‐tert‐butylcalix[4]arene(OMe)(OH)₂(OLi)]₂·4MeCN, (I), crystallizes with the complex across a centre of symmetry and with four molecules of unbound acetonitrile of crystallization per complex. Tetraacetonitrilebis(μ‐5,11,17,23‐tetra‐tert‐butyl‐26,28‐dihydroxy‐25,27‐dioxidocalix[4]arene)tetralithium(I) acetonitrile octasolvate, [Li₄(C₄₄H₅₄O₄)₂(C₂H₃N)₄]·8C₂H₃N or {p‐tert‐butylcalix[4]arene(OH)₂(OLi)[OLi(NCMe)₂]}₂·8MeCN, (II), also crystallizes with the complex lying across a centre of symmetry and contains eight molecules of unbound acetonitrile per complex plus four more directly bound to two of the lithium ions, two on each ion. The cores of both complexes are partially supported by O—H...O hydrogen bonds. The methoxy methyl groups in (I) prevent the binding of any more than two Li⁺ ions, while the corresponding two O‐atom sites in (II) bind an extra Li⁺ ion each, making four in total. The calixarene cone adopts an undistorted cone conformation in (I), but an elliptical one in (II).     

Oxalato‐ und Quadratato‐Komplexe hochkoordinierter Metallionen: Die Raumnetzstrukturen von La2(C2O4)(C4O4)2(H2O)8 · 2,5 H2O und K[Bi(C2O4)2] · 5 H2O

Oxalato‐ and Squarato‐Bridged Threedimensional Networks: The Crystal Structures of La₂(C₂O₄)(C₄O₄)₂(H₂O)₈ · 2.5 H₂O and K[Bi(C₂O₄)₂] · 5 H₂O The title compounds have been formed by hydrolysis of amino‐ and thioderivatives of squaric acid in the presence of La^III and Bi^III ions. Both compounds are threedimensional coordination polymers in the solid state, as shown by single crystal X‐ray crystallography. In La₂(C₂O₄)(C₄O₄)₂(H₂O)₈ · 2.5 H₂O oxalato‐bridged pairs of LaO₉ polyhedra are connected with identical neighbouring polyhedra by squarate ions. In K[Bi(C₂O₄)₂] · 5 H₂O each Bi atom is fourfold linked to other Bi atoms by the oxalate ions. The resulting 3D network shows a diamond‐like topology with square‐shaped channels. In both structures the channels are partially filled by water molecules.     

Koordinationspolymere 1, 2‐Dithiooxalato‐ und 1, 2‐Dithioquadratato‐Komplexe. Synthese und Strukturen von [BaCr2(bipy)2(1, 2‐dtox)4(H2O)2], [Ni(cyclam)(1, 2‐dtsq)]·2DMF, [Ni(cyclam)Mn(1, 2‐dtsq)2(H2O)2]·2H2O und [H3O][H5O2][Cu(cyclam)]3[Cu2(1, 2‐dtsq)3]2

Coordination Polymeric 1, 2‐Dithiooxalato and 1, 2‐Dithiosquarato Complexes. Syntheses and Structures of [BaCr₂(bipy)₂(1, 2‐dtox)₄(H₂O)₂], [Ni(cyclam)(1, 2‐dtsq)]·2DMF, [Ni(cyclam)Mn(1, 2‐dtsq)₂(H₂O)₂]·2H2₂, and [H₃O][H₅O₂][Cu(cyclam)]₃[Cu₂(1, 2‐dtsq)₃]₂ 1, 2‐Dithioxalate and 1, 2‐dithiosquarate ions have a pair of soft and hard donor centers and thus are suited for the formation of coordination polymeric complexes containing soft and hard metal ions. The structures of four compounds with building blocks containing these ligands are reported: In [BaCr₂(bipy)₂(1, 2‐dtox)₄(H₂O)₂] Barium ions and pairs of Cr(bipy)(1, 2‐dtox)₂ complexes form linear chains by the bisbidentate coordination of the dithiooxalate ligands towards Ba²⁺ and Cr³⁺. In [Ni(cyclam)(1, 2‐dtsq)]·2DMF short NÖH···O hydrogen bonds link the NiS₂N₄‐octahedra with C_2v‐symmetry to an infinite chain. In [Ni(cyclam)Mn(1, 2‐dtsq)₂(H₂O)₂]·2H₂O the 1, 2‐dithiosquarato ligand shows a rare example of S‐coordination towards manganese(II). The sulfur atoms of cis‐MnO₂S₄‐polyedra are weakly coordinated towards the axial sites of square‐planar NiN₄‐centers, thus forming a zig‐zag‐chain of Mn···Ni···Mn···Ni polyhedra. [H₃O][H₅O₂][Cu (cyclam)]₃[Cu₂(1, 2‐dtsq)₃]₂ contains square planar [Cu^II(cyclam)]²⁺ ions and dinuclear [Cu^I₂(1, 2‐dtsq)₃]^4— ions. Here each copper atom is trigonally planar coordinated by S‐donor atoms of the ligands. The Cu…Cu distance is 2.861(4)Å.     

Crystal Structures of [Mn2(H2O)4(phen)2(C4H4O4)2] · 2 H2O and [Mn(phen)2(H2O)2][Mn(phen)2(C4H4O4)](C4H4O4) · 7 H2O

Reactions of 1,10‐phenanthroline monohydrate, Na₂C₄H₄O₄ · 6 H₂O and MnSO₄ · H₂O in CH₃OH/H₂O yielded a mixture of [Mn₂(H₂O)₄(phen)₂(C₄H₄O₄)₂] · 2 H₂O ( 1 ) and [Mn(phen)₂(H₂O)₂][Mn(phen)₂(C₄H₄O₄)](C₄H₄O₄) · 7 H₂O ( 2 ). The crystal structure of 1 (P1 (no. 2), a = 8.257(1) Å, b = 8.395(1) Å, c = 12.879(2) Å, α = 95.33(1)°, β = 104.56(1)°, γ = 106.76(1)°, V = 814.1(2) ų, Z = 1) consists of the dinuclear [Mn₂(H₂O)₄(phen)₂(C₄H₄O₄)₂] molecules and hydrogen bonded H₂O molecules. The centrosymmetric dinuclear molecules, in which the Mn atoms are octahedrally coordinated by two N atoms of one phen ligand and four O atoms from two H₂O molecules and two bis‐monodentate succinato ligands, are assembled via π‐π stacking interactions into 2 D supramolecular layers parallel to (101) (d(Mn–O) = 2.123–2.265 Å, d(Mn–N) = 2.307 Å). The crystal structure of 2 (P1 (no. 2), a = 14.289(2) Å, b = 15.182(2) Å, c = 15.913(2) Å, α = 67.108(7)°, β = 87.27(1)°, γ = 68.216(8)°, V = 2934.2(7) ų, Z = 2) is composed of the [Mn(phen)₂(H₂O)₂]²⁺ cations, [Mn(phen)₂(C₄H₄O₄)] complex molecules, (C₄H₄O₄)^2– anions, and H₂O molecules. The (C₄H₄O₄)^2– anions and H₂O molecules form 3 D hydrogen bonded network and the cations and complex molecules in the tunnels along [001] and [011], respectively, are assembled via the π‐π stacking interactions into 1 D supramolecular chains. The Mn atoms are octahedrally coordinated by four N atoms of two bidentate chelating phen ligands and two water O atoms or two carboxyl O atoms (d(Mn–O) = 2.088–2.129 Å, d(Mn–N) = 2.277–2.355 Å). Interestingly, the succinato ligands in the complex molecules assume gauche conformation bidentately to chelate the Mn atoms into seven‐membered rings.     

Comparative study of two chemically isostructural polymers: [Cu2(VO2)(HPO4)2(NO3)(bpy)2]·2H2O/H3PO4 (bpy is 2,2′‐bi­pyridine)

The title compounds, poly­[bis(2,2′‐bi­pyridine)­bis(μ₃‐hydrogen phosphato)­nitratodi‐μ₂‐oxo‐dicopper(II)­vanadium dihydrate], [Cu₂(VO₂)(HPO₄)₂(NO₃)(C₁₀H₈N₂)₂]·2H₂O, (I), and poly­[bis(2,2′‐bi­pyridine)­bis(μ₃‐hydrogen phosphato)­nitratodi‐μ₂‐oxo‐dicopper(II)­vanadium phospho­ric acid solvate], [Cu₂(VO₂)(HPO₄)₂(NO₃)(C₁₀H₈N₂)₂]·H₃PO₄, (II), were obtained by similar hydro­thermal methods but under different crystallization conditions. The trinuclear entity which serves as the basic unit in both structures presents two independent Cu^II ions immersed in similar square‐pyramidal N₂O₃ environments plus an octahedral VO₆ core and is organized into a one‐dimensional polymer, which is essentially identical in the two structures. The compounds are stabilized by different solvates, viz. two crystallization water mol­ecules in (I) and a phospho­ric acid mol­ecule in (II), which provide the main structural differences through the diversity of interchain interactions in which they serve as bridges.     

A New Preparative Route of the “Stepped‐Cubane” Tetranuclear Copper(II) Compound, [Cu4(μ2‐OH)2(μ3‐OH)2Cl2(bipy)4]Cl2 · 6H2O

The compound [Cu₄(μ₂‐OH)₂(μ₃‐OH)₂Cl₂(bipy)₄]Cl₂ · 6H₂O ( 1 ) was obtained by recrystallization of [Cu(HB)₂(2, 2′‐bipy)] · H₂O (H₂B = diphenylglycolic acid) from EtOH/CH₂Cl₂ and their structure has been determined by single‐crystal X‐ray analysis. The cationic complex may be described as based on a Cu₄(OH)₄ core with a “stepped cubane” structure. The coordination polyhedron around each copper is a distorted square pyramid. The tetranuclear units are linked in the crystal by C‐H…Cl hydrogen bonds and by π‐π interactions between bipyridine rings. IR data are also presented.     

RbCrIII(C2O4)2·2H2O,Cs2Mg(C2O4)2·4H2O and Rb2CuII(C2O4)2·2H2O: three new complex oxalate hydrates

Rubidium chromium(III) dioxalate dihydrate [di­aqua­bis(μ‐oxalato)­chromium(III)­rubidium(I)], [RbCr(C₂O₄)₂(H₂O)₂], (I), and dicaesium magnesium dioxalate tetrahydrate [tetra­aqua­bis(μ‐oxalato)­magnesium(II)­dicaesium(I)], [Cs₂Mg(C₂­O₄)₂(H₂O)₄], (II), have layered structures which are new among double‐metal oxalates. In (I), the Rb and Cr atoms lie on sites with imposed 2/m symmetry and the unique water molecule lies on a mirror plane; in (II), the Mg atom lies on a twofold axis. The two non‐equivalent Cr and Mg atoms both show octahedral coordination, with a mean Cr—O distance of 1.966 Å and a mean Mg—O distance of 2.066 Å. Dirubid­ium copper(II) dioxalate dihydrate [di­aqua­bis(μ‐oxalato)­copper(II)­dirubidium(I)], [Rb₂Cu(C₂O₄)₂(H₂O)₂], (III), is also layered and is isotypic with the previously described K₂‐ and (NH₄)₂Cu^II(C₂O₄)₂·2H₂O compounds. The two non‐equivalent Cu atoms lie on inversion centres and are both (4+2)‐coordinated. Hydro­gen bonds are medium‐strong to weak in the three compounds. The oxalate groups are slightly non‐planar only in the Cs–Mg compound, (II), and are more distinctly non‐planar in the K–Cu compound, (III).     

Bis[trans‐dibromo(2,2‐di­methylpropane‐1,3‐diamine‐κ2N,N′)chromium(III)] dibromide hydrogen perchlorate hexahydrate

In the title compound, [CrBr₂(C₅H₁₄N₂)₂]₂Br₂·HClO₄·6H₂O, there are two independent Cr^III complex cations which are conformational isomers of each other. The Cr atoms lie respectively on a center of symmetry and on a mirror plane and have octahedral environments, coordinated by the N atoms of two 2,2‐di­methylpropane‐1,3‐diamine ligands and by two Br atoms in trans positions. The Cr—N and Cr—Br bond lengths are in the ranges 2.078 (3)–2.089 (3) and 2.4495 (9)–2.5017 (9) Å, respectively. The crystal structure consists of two Cr^III complex cations, two Br^? anions, a (ClO₄)^? anion and an [H₁₃O₆]⁺ hydrogen‐bonded cluster cation.     

Macromolecular Self‐Assembly of Organotin(IV) Squarates and Croconates – Preparation and Crystal Structures of [SnMe2(H2O)2]C4O4, [SnMe3]2C4O4, and [SnMe3(H2O)]2C5O5

The new organotin(IV) squarates and croconates [SnMe₂(H₂O)₂]C₄O₄ ( 1 ), [SnMe₃]₂C₄O₄ ( 2 ), and [SnMe₃(H₂O)]₂C₅O₅ ( 3 ), were prepared by salt metathesis from the appropriate sodium salts, and characterized by single‐crystal X‐ray diffraction and infrared spectroscopy. While 1 and 2 are coordination polymers with bridging C₄O₄^2– anions, compound 3 exists as a monomer in the solid state. In the hydrated compounds 1 and 3 , the molecules are interconnected by various types of O–H ··· O bridges between non‐coordinated carbonyl oxygen atoms and water ligands, resulting in a supramolecular layer ( 1 , 2 ) or network structure ( 3 ), respectively.     

Two oxo complexes with tetra­nuclear [Fe4(μ3‐O)2]8+ and trinuclear [Fe3(μ3‐O)]7+ units

Two new oxo complexes, namely hexa‐μ₂‐acetato‐acetato­aquabis­(di‐3‐pyridylamine)di‐μ₃‐oxo‐tetra­iron(III) chloride mono­hydrate ethanol 1.25‐solvate, [Fe₄(C₂H₃O₂)₇O₂(C₁₀H₉N₃)₂(H₂O)]Cl·1.25C₂H₆O·H₂O, (I), containing a tetra­nuclear [Fe₄(μ₃‐O)₂]⁸⁺ unit, and 2‐methyl­imidazolium hexa‐μ₂‐acetato‐acetatodiaqua‐μ₃‐oxo‐triiron(III) chloride dihydrate, (C₄H₇N₂)[Fe₃(C₂H₃O₂)₇O(H₂O)₂]Cl·2H₂O, (II), with a trinuclear [Fe₃(μ₃‐O)]⁷⁺ unit, are presented. Both structures are formed by two well differentiated entities, viz. a compact isolated cluster composed of Fe^III ions coordinated to O²⁻ and CH₃CO₂⁻ anions, and an external group formed by a central Cl⁻ ion surrounded by different solvent groups to which the anion is bound through hydrogen bonding. In the case of (I), charge balance cannot be achieved within the groups, so the structure is macroscopically ionic; in the case of (II), in contrast, each group is locally neutral owing to the inter­nal compensation of charges. The trinuclear complex crystallizes with the metal cluster, chloride anion and 2‐methyl­imidazolium cation bisected by a crystallographic mirror plane.     

K2[Mo2O4(C2O4)2(H2O)2]·3H2O

The crystal and molecular structure of dipotassium di‐μ‐oxo‐bis[aqua(oxalato‐O¹,O²)oxomolybdenum(III)] trihydrate, K₂­[Mo₂O₄(C₂O₄)₂(H₂O)₂]·3H₂O, has been determined from X‐ray diffraction data. In the dimeric anion, which has approximate twofold symmetry, each Mo atom is in a distorted octahedral coordination, being bonded to one terminal oxo‐O atom, two bridging O atoms, two O atoms from the oxalato ligand and one from the water mol­ecule. Bond lengths trans to the multiple‐bonded terminal oxo ligand are larger than those in the cis position, confirming the trans influence as a generally valid rule.     

[Mn12O12(O2CMe)12(NO3)4(H2O)4]: facile synthesis of a new type of Mn12 complex

The title dodecanuclear Mn complex, namely dodeca‐μ₂‐acetato‐κ²⁴O:O′‐tetraaquatetra‐μ₂‐nitrato‐κ⁸O:O′‐tetra‐μ₄‐oxido‐octa‐μ₃‐oxido‐tetramanganese(IV)octamanganese(III) nitromethane tetrasolvate, [Mn₁₂(CH₃COO)₁₂(NO₃)₄O₁₂(H₂O)₄]·4CH₃NO₂, was synthesized by the reaction of Mn²⁺ and Ce⁴⁺ sources in nitromethane with an excess of acetic acid. This compound is distinct from the previously known single‐molecule magnet [Mn₁₂O₁₂(O₂CMe)₁₆(H₂O)₄], synthesized by Lis [Acta Cryst. (1980), B 36 , 2042–2044]. It is the first Mn₁₂‐type molecule containing nitrate ligands to be directly synthesized without the use of a preformed cluster. Additionally, this molecule is distinct from all other known Mn₁₂ complexes due to intermolecular hydrogen bonds between the nitrate and water ligands, which give rise to a three‐dimensional network. The complex is compared to other known Mn₁₂ molecules in terms of its structural parameters and symmetry.     

A Zigzag‐Shaped Yb4 Cluster Bridged by Pyridine‐2,6‐dimethanol

A homometallic lanthanide tetranuclear cluster, namely [Yb₄(pdmH)₂(pdm)₄ (PhCO₂)₂(PhCO₂H)₂(H₂O)₂] · PhCO₂H · 0.25MeOH ( 1 ) (pdmH₂ = pyridine‐2,6‐dimethanol) was prepared and structurally characterized. Single‐crystal X‐ray analysis revealed that complex 1 has a tetranuclear core with a zigzag arrangement. Magnetic properties of complex 1 were also investigated.     

Lanthanoid‐Peroxo‐Komplexe mit μ3‐η2:η2:η2‐(O22—)‐Koordination. Die Kristallstrukturen von [Ln4(O2)2Cl8(Py)10] · Py mit Ln = Sm,Eu, Gd

Lanthanoid Peroxo Complexes with μ₃‐η²:η²:η²‐(O₂^2—) Coordination. Crystal Structures of [Ln₄(O₂)₂Cl₈(Py)₁₀] · Py mit Ln = Sm, Eu, Gd The four‐nuclear peroxo complexes [Ln₄(O₂)₂Cl₈(Py)₁₀]·py (py = pyridine) with Ln = Sm ( 1 ·py), Eu ( 2 ·py) und Gd ( 3 ·py) are formed as pale yellow ( 1 ·py) and colourless ( 2 ·py and 3 ·py) crystals by action of atmospheric oxygen on heated solutions of the anhydrous trichlorides LnCl₃ in pyridine/ diacetone alcohol (4‐hydroxy‐4‐methyl‐2‐pentanone). According to the X‐ray structural analyses the three complexes crystallize isostructural in the triclinic space group PP1¯ with two formula units per unit cell. 1—3 form centrosymmetrical molecular structures, in which the four lanthanoid atoms in coplanar array are linked via the two peroxo groups in a hitherto unobserved μ₃‐η²:η²:η² coordination. Additionally, they are bonded by four �μchloro bridges. Two of the Ln atoms complete their coordination sphere by three pyridine molecules each, the other two by two chlorine atoms and two pyridine molecules. The gadolinium compound is additionally characterized by its complete vibrational spectrum (i.r. and Raman).     

[Ba6(C2H3O2)12(H2O)3.5], a new hydrate of barium acetate

A new barium acetate phase, di‐μ₅‐acetato‐tri‐μ₄‐acetato‐tri‐μ₃‐acetato‐tri‐μ₂‐acetato‐μ₂‐acetato‐triaquahemiaquahexabarium(II), of analytical formula [Ba₆(C₂H₃O₂)₁₂(H₂O)_3.5], is described. The asymmetric unit contains six independent Ba centres with coordination numbers varying from 7 to 10 arising from bonding to 12 crystallographically independent acetate ligands and four molecules of water, one of which is disordered over two sites both of occupancy 0.5. Bonding to the acetate ligands creates a completely connected three‐dimensional structure. All H atoms of the water molecules participate in hydrogen bonding.     

[Mn(H2O)2]4[HNC5H4(COO)]2[C6H2(COO)4]2·4H2O — Ein dreidimensionales Koordinationspolymer mit Gastwassermolekülen in kanalartigen Hohlräumen

[Mn(H₂O)₂]₄[HNC₅H₄(COO)]₂[C₆H₂(COO)₄]₂·4H₂O — A Three‐dimensional Coordination Polymer with Guest Water Molecules in Channel‐like Voids Single crystals of [Mn(H₂O)₂]₄[HNC₅H₄(COO)]₂[C₆H₂(COO)₄]₂·4H₂O have been prepared in aqueous solution at 55 °C. Space group P1¯ (no. 2), a = 999.7(2), b = 1314.4(2), c = 1645.8(2) pm, α = 101.096(8)°, β = 92.796(14)°, γ = 96.03(2)°, V = 2.1053(5) nm³, Z = 2. There are four unique Mn²⁺ which are coordinated in a distorted, octahedral manner by two water molecules, three oxygen atoms of the pyromellitate anions and one oxygen atom of isonicotinic acid (Mn—O 208.6(2) — 227.3(3) pm). The connection of Mn²⁺ and [C₆H₂(COO)₄]^4— yields a three‐dimensional coordination polymer with two different, channel‐like voids extending parallel to [110]. The first channel accomodates water molecules, the second channel is filled by isonicotinic acid molecules. Thermogravimetric analysis in air revealed that the loss of water of crystallisation occurs in two steps between 97 and 200 °C. The dehydrated sample was stable between 200 and 340 °C. Further decomposition yielded Mn₃O₄.     

Synthesis and Characterization of [Mn3(ppi)2(μ‐OAc)4(H2O)2] · 2MeOH — Unusual Structural Properties of a Trinuclear Oxygen‐Rich Manganese Complex

The trinuclear manganese(II) complex [Mn₃(ppi)₂(μ‐OAc)₄(H₂O)₂]·2MeOH ( 1 ) (Hppi = 2‐pyridylmethyl‐2‐hydroxyphenylimine) is prepared by dissolving two equivalents of Hppi (from the Schiff Base reaction of aminophenol and pyridine‐2‐carboxaldehyde) in acetonitrile and three equivalents of Mn(OAc)₂·4H₂O in methanol and combining both solutions. The resulting red precipitate was recrystallized to yield red crystals suitable for single crystal X‐ray diffraction. Compound 1 crystallizes in the triclinic space group P1¯ (no. 2), with a = 9.691(2), b = 10.683(2), c = 11.541(2)Å, α = 63.19(3)°, β = 67.47(3)°, γ = 69.11(3)°, V = 960.2(3)ų, and Z = 1. The binding mode of carboxylate in 1 represents a model for a transition state between symmetric syn, syn, anti‐μ₂‐carboxolato‐O‐ and syn, anti‐μ₂‐carboxylato‐O, O′‐coordination. Therefore a rare binding mode for the phenomenon of the carboxylate shift is realized. Furthermore the complex is stabilized by a distinctive hydrogen bonding pathway.     

Preparation,Crystal Structure and Vibrational Spectra of Ca2P2O6·2H2O and [Ca(H2O)3(H2P2O6)]·0.5(C12H24O6)·H2O

The calcium salts Ca₂P₂O₆ · 2H₂O ( 1 ) and [Ca(H₂O)₃(H₂P₂O₆)] · 0.5(C₁₂H₂₄O₆) · H₂O ( 2 ) were prepared and structurally characterized by single‐crystal X‐ray diffraction. Compound 1 crystallizes in the orthorhombic space group Pbca and compound 2 in the monoclinic space group P2₁/n. The crystal structure of compound 1 consists of chains of edge‐sharing [CaO₇] polyhedra linked by hypodiphosphate(IV) anions to form a three‐dimensional network. The crystal structure of compound 2 consists of alternated layers of crown ether and water molecules and respective ionic units. Within the layers of ionic units the Ca²⁺ cations are octahedrally coordinated by three monodentate dihydrogenhypodiphosphate(IV) anions and three water molecules. The IR/Raman spectra of the title compounds were recorded and interpreted, especially with respect to the [P₂O₆]^4– and [H₂P₂O₆]^2– groups. The phase purity of 2 was verified by powder diffraction measurements.