Syntheses and structures of the MOF-type series of metal 1,4,5,8,-naphthalenetetracarboxylates M2(OH)2[C14O8H4] (Al,Ga, In) with infinite trans-connected M–OH–M chains (MIL-122)

Three new isostructural MOF-type compounds (named MIL-122) have been obtained from the hydrothermal reaction at 210 °C for 24 h of the 1,4,5,8-naphthalenetetracarboxylic acid with aluminum, gallium or indium source in water. The structures of the compounds M₂(OH)₂[C₁₄H₄O₈] (M = Al, Ga, In) have been solved ab initio from powder X-ray diffraction analysis using the synchrotron radiation (Soleil; station CRISTAL). The three-dimensional organic–inorganic framework exhibits infinite straight chains of metal-centered octahedra sharing trans corners linked to each other through the 1,4,5,8-naphthalenetetracarboxylate ligand. The cations Al, Ga or In, are coordinated by four oxygen atoms coming from the carboxyl groups and two bridging hydroxyl groups μ₂-OH, located in trans position in the octahedral surrounding. The compounds characterized by thermogravimetric and thermodiffraction analyses are thermally stable up to 440, 460 and 380 °C, for Al, Ga and In, respectively. Crystal data: monoclinic cell; P2₁/c (n°14); for MIL-122 (Al): a = 9.5174(2), b = 10.0706(1), c = 6.6465(2) Å, β = 91.2614(5)°, V = 636.878(2) Å³, Z = 2; for MIL-122 (Ga): a = 9.6501(1), b = 10.0585(1), c = 6.75069(9) Å, β = 92.4786(9)°, V = 654.65(1) Å³, Z = 2; for MIL-122 (In): a = 9.92359(5), b = 10.19765(7), c = 7.19357(4) Å, β = 727.034(8)°, V = 727.034(8)ų, Z = 2.     

Comparative study of two layered lanthanide dicarboxylates based on europium(III) dimers

The new rare-earth dicarboxylate solid Eu₂(H₂O)₄{C₆H₁₀–(CO₂)₂}₃·2H₂O or MIL-94 has been isolated under hydrothermal conditions. Its layered structure, which was solved using X-ray powder diffraction data, is built up from dimers of nine-coordinated edge-sharing polyhedra linked through 1,3-cyclohexane dicarboxylate (1,3-CHC) moieties. A comparative study of MIL-94 and the layered lanthanide dicarboxylate EuBDC or Eu₂(H₂O)₂{C₆H₄–(CO₂)₂}₃, which is built up from dimers of corner-sharing polyhedra and 1,3-benzenedicarboxylate (1,3-BDC) linkers, is also reported. Crystal data for MIL-94: orthorhombic space group Pnma (no. 62) with a = 8.8470(1) Å, b = 25.0148(1) Å, c = 14.3716(4) Å and Z = 4. MIL stands for Material Institut Lavoisier.     

Synthesis,structure and solid state NMR analysis of a new templated titanium(III/IV) fluorophosphate

The title compound MIL-131 (MIL stands for Material from Institut Lavoisier) was prepared hydrothermally (4 days, 473 K, autogenous pressure) in the presence of an organic base (N((CH₂)₂NH₂)₃). The structure of MIL-131 or Ti^IIITi^IV(OH)F₄(HPO₄)·(PO₄)·(N((CH₂)₂NH₃)₃) has been determined ab initio from X-Ray synchrotron powder diffraction data using simulated annealing methods and was refined in the triclinic space group P-1 (no. 2). MIL-131 exhibits a one-dimensional structure built up from inorganic chains of corner sharing TiO₅(OH) titanium(III) octahedra and PO₄ and HPO₄ phosphate tetrahedra, related to TiO₂F₄ titanium octahedra. Protonated triamine cations are located between the inorganic motifs, and interact strongly with the mineral network through hydrogen bondings both with terminal fluorine atoms and hydroxo or oxo groups. Multinuclear solid state NMR has allowed a clear attribution of the protons, fluoride, and phosphate groups environment within the framework of MIL-131. The large values of chemical shift anisotropy together with the absence of any ¹³C NMR response confirmed the presence of paramagnetic titanium(III) species deduced from the crystal structure. Finally, 2D MAS ¹H-³¹P CP-HETCOR NMR correlation experiment gives some insight on the nature of the intra-framework hydrogen bonding.Crystal data for MIL-131: a = 14.109(1) Å, b = 8.462(3) Å, c = 7.179(1) Å, α = 93.772(1)°, β = 96.566(2)°, γ = 98.004(1)°, V = 840.36(2) ų, z = 2.     

Organic derivatives of tin (II/IV): Investigation of their structure

The structures of tin(II)-oxalate, tin(IV)Na–EDTA and tin(IV)Na₈-inositol hexaphosphate were investigated using XRD analysis. Samples were identified using the Mössbauer study, thermal analysis and FTIR spectrometry. The Mössbauer study determined two different oxidation states of tin atoms, and consequently two different tin surroundings in the end products. The tin oxalate was found to be orthorhombic with space group Pnma, a=9.2066(3) Å, b=9.7590(1) Å, c=13.1848(5) Å, V=1184.62 Å³ and Z=8. SnNa–EDTA was found to be monoclinic with space group P2₁/c₁, a=10.7544(3) Å, b=10.1455(3) Å, c=16.5130(6) Å, β=98.59(2)°, V=1781.50(4) Å³ and Z=4. Sn(C₆H₆Na₈O₂₄P₆) was found to be amorphous.     

Two fumarato-bridged Co(II) coordination polymers: syntheses,crystal structures and properties of Co(H2O)4L and [Co3(H2O)4(OH)2L2]·2H2O with H2LHOOCCHCHCOOH

Two fumarato-bridged Co(II) coordination polymers Co(H₂O)₄L 1 and [Co₃(H₂O)₄(OH)₂L₂]·2H₂O 2 with H₂LHOOCCH CHCOOH were prepared. Complex 1 consists of polymeric chains _∞¹[Co(H₂O)₄(C₄H₂O₄)_2/2], which result from octahedrally coordinated Co atoms bridged by bis-monodentate fumarate anions and are assembled by interchain hydrogen bonds. Within 2, the edge-shared Co₂O₁₀ bi-octahedra are connected to the CoO₆ octahedra to form 1D cobalt oxide chains and 3D open framework generated from the chains inter-linked by bis-bidentate fumarate anions displays rhombic tunnels, which are filled with the lattice H₂O molecules. Thermal and magnetic behaviors of both the title coordination polymers are discussed. Crystal data: (1) monoclinic, P2₁/c, Z=4, a=7.493(1) Å, b=14.377(1) Å, c=7.708(1) Å, β=99.54(1)°, V=818.9(2) Å³, R₁=0.0304, and wR₂=0.0669 for 1487 observed reflections (I⩾2σ(I)) out of 1877 unique reflections; (2) monoclinic, P2₁/c, Z=2, a=6.618(1) Å, b=8.172(2) Å, c=15.578(3) Å, β=96.30(3)°, V=837.4(3) Å³, R₁=0.0360 and wR₂=0.0663 for 1442 observed reflections (I⩾2σ(I)) out of 1927 unique reflections.     

[H4tren]3/2·(Al6F24)·3H2O,the most condensed fluoride in the Al(OH)3-tren-HFaq.-ethanol system

The most condensed crystalline fluoride that appears in the Al(OH)₃-tren-HF_aq.-ethanol system at 190 °C is found to be [H₄tren]_3/2·(Al₆F₂₄)·3H₂O. The structure is monoclinic, P2₁/c, with a = 21.939(1) Å, b = 6.7180(2) Å, c = 23.329(1) Å, β = 111.324(2)°. _∞(Al₆F₂₄) chains result from the connection of (Al₇F₃₀)⁹⁻ polyanions by opposite AlF₆ octahedra. Hydrogen bonds are established between the _∞(Al₆F₂₄) chains and ordered or disordered [H₄tren]⁴⁺ cations and water molecules.     

Two novel Keggin tungstocobaltates grafted by cobaltII complex group(s): K[Co(phen)2(H2O)]2[HCoW12O40]·2H2O and [Co(2,2′-bipy)3]1.5{[Co(2,2′-bipy)2(H2O)][HCoW12O40]}·0.5H2O

Two novel inorganic–organic hybrid compounds composed of Keggin tungstocobaltate framework and cobalt(II)–N coordination complexes, K[Co(phen)₂(H₂O)]₂[HCoW₁₂O₄₀]·2H₂O (1) (phen = 1,10-phenanthroline) and [Co(2,2′-bipy)₃]_1.5{[Co(2,2′-bipy)₂(H₂O)][HCoW₁₂O₄₀]·0.5H₂O (2) (bipy = bipyridine), have been synthesized under hydrothermal conditions by directly using Keggin POMs as starting materials, which were characterized by elemental analyses, IR, TG analyses and X-ray single crystal diffraction. Crystal data for compound 1: C₄₈H₄₁Co₃KN₈O₄₄W_12, triclinic, space group P-1, a = 10.918(5) Å, b = 13.401(5) Å, c = 13.693(5) Å, α = 69.291(5)°, β = 71.568(5)°, γ = 78.421(5)°, V = 1768.9(12) Å³, Z = 1; for compound 2: C₁₃₀H₁₀₄Co₇N₂₆O₈₃W_24, orthorhombic, space group, C2/c, a = 46.839(9) Å, b = 14.347(3) Å, c = 26.147(5) Å, α = β = γ = 90°, V = 17,570(6) Å³, Z = 4. Compound 1 exhibits a pseudo-1D chainlike structure, in which potassium ions act as linkages of Keggin unit doubly grafted by [Co(phen)₂(H₂O)] complex. Compound 2 represents a [Co(2,2′-bipy)₂(H₂O)]²⁺ mono-grafted Keggin tungstocobaltate derivative with 1.5[Co(2,2′-bipy)₃]²⁺ countercations. The cyclic voltammetric behavior of 1-CPE is similar to the parent 3-CPE, but the cyclic voltammetric behavior of Co^II shows a little difference. Variable-temperature magnetic susceptibility measurement of compound 1 demonstrates the presence of antiferromagnetic interactions.     

Inhibitors for magnesium corrosion: Metal organic frameworks

Electrochemical measurements demonstrate that magnesium surfaces can be protected by alkyl carboxylate. In a nearly neutral pH solution of sodium decanoate, the reduced corrosion rate and a passivation behaviour are attributed to the formation of Mg(C₁₀H₁₉O₂)₂(H₂O)₃ (Mg(C10)₂) at the magnesium surface whereas heptanoate Mg(C₇H₁₃O₂)₂(H₂O)₃ (Mg(C7)₂) is not efficient in such media. The crystal structures of the two metal carboxylates Mg(C7)₂ and Mg(C10)₂ are determined by X-ray diffraction. Single crystal data: Mg(C7)₂, P2₁/a, a = 9.130(5) Å, b = 8.152(5) Å, c = 24.195(5) Å, β = 91.476(5)°, V = 1800.3(15) Å³, D_x = 1.242 g cm⁻³, Z = 4. Synchrotron powder data: Mg(C10)₂, P2₁/a, a = 9.070(3) Å, b = 8.165(1) Å, c = 32.124(1) Å, β = 98.39(1)°, V = 2353.85(8) Å³, D_x = 1.188 g cm⁻³, Z = 4. Their layered structures are quite similar and differ mainly by the length of the hydrophobic chains. They consist of two planes of O-octahedra centred by Mg atoms, parallel to (001). The distorted octahedra are constituted by three oxygen atoms from carboxylate groups and by three oxygen atoms coming from water molecules. The layers are connected by hydrogen bonds. The carboxylate chains are located perpendicularly and on both sides of these planes. One carboxylate chain is bridging the Mg atom along [010] while the other is monodendate. The presence of structural water is confirmed by thermal analyses.     

Copper and cadmium phosphonates based on 2-quinolinephosphonate

Hydrothermal reactions of 2-quinolinephosphonic acid (1) and CuSO₄ or CdSO₄ result in two new compounds with formula Cu(2-C₉H₆NPO₃) (2) and Cd(2-C₉H₆NPO₃)(H₂O) (3). Compound 2 has a layer structure in which dimers of edge-sharing {CuO₄N} square-pyramids are linked by {CPO₃} tetrahedra through corner sharing. Compound 3 shows a new type of layer structure where chains of corner sharing {CdO₅N} octahedra are connected by {CPO₃} tetrahedra into an inorganic layer. The quinoline groups fill in the inter-layer spaces in both cases. Crystal data for 1: monoclinic, space group P2₁/c, a = 10.270(2) Å, b = 13.566(3) Å, c = 6.9818(16) Å, β = 101.916(4)°, V = 951.8(4) Å³, Z = 4. For 2: monoclinic, space group P2₁/c, a = 13.976(3) Å, b = 7.9398(18) Å, c = 7.8687(18) Å, β = 101.150(5)°, V = 856.7(3) Å³, Z = 4. For 3: monoclinic, space group P2₁/c, a = 17.164(4) Å, b = 5.4870(12) Å, c = 10.850(2) Å, β = 101.557(4)°, V = 1001.1(4) Å³, Z = 4. The magnetic measurement on 2 reveals a dominant antiferromagnetic exchange coupling between the Cu(II) centers. A quasi-reversible electrochemical reaction is observed for complex 2 immobilized on the surface of GC electrode, corresponding to the redox couple Cu²⁺/Cu⁺. The fluorescent properties of 1–3 are also investigated.     

A new calcium trimellitate coordination polymer with a chain-like structure

The calcium trimellitate, Ca(H₂O)[(O₂C)₂–C₆H₃–CO₂H], was hydrothermally synthesized from a mixture of calcium hydroxide, 1,2,4-benzenetricarboxylic (or trimellitic) acid and water at 180 °C for 24 h (under autogenous pressure). Its crystal structure has been determined by single-crystal X-ray diffraction analysis using synchrotron radiation (station 9.8, SRS Daresbury, UK). It consists of infinite chains of calcium bicapped trigonal prismatic polyhedra connected to each other through the 1,2,4-benzenetricarboxylate ligand. The eight-fold coordinated calcium cation is bonded to one terminal water molecule, two carboxylate groups with a chelating conformation and three carboxylate groups in a monodentating mode. One of the monodentate carboxylate is terminal with the occurrence of protonated C–OH bonding.Triclinic space group P-1 with a = 6.9073(4) Å, b = 6.9917(4) Å, c = 10.3561(6) Å, α = 87.178(1)°, β = 83.233(1)°, γ = 69.576(1)°, V = 465.41(5) Å³.     

Synthesis and characterization of a novel three-dimensional open-framework: Metal diphosphonate,Zn[HO3PCH2(C6H4)CH2PO3H]

A novel zinc diphosphonate, Zn[HO₃PCH₂(C₆H₄)CH₂PO₃H] (1) was synthesized from tetraethyl para-xylylenediphosphonate, Et₂O₃PCH₂C₆H₄CH₂PO₃Et₂, and Zn (AcO)₂·2H₂O under solvothermal conditions. The structure of compound 1 was determined by single-crystal X-ray diffraction, which reveals that the structure crystallizes in the monoclinic space group C2/c (No. 15), with a = 22.4844(19) Å, b = 6.4361(5) Å, c = 8.1194(7) Å, β = 102.595(2)°, V = 1146.70(16) Å³, T = 298(2) K, Z = 8. The novel three-dimensional (3D) construction is simply built up from linear inorganic chains of corner-sharing four-rings of tetrahedral [ZnO₄] and [PO₃C] which connected adjacent chains by the organophosphorus ligand para-xylylenediphosphonate. The framework has 10 Å × 4 Å (containing the van der Waals radii of atoms) channels running along the b-axis.     

A new intersecting tunnel structure in the AIMIII[PO3(OH)]2 series for AI = Ag,MIII = In: Analysis of structural relationships

A new indium hydroxyphosphate containing silver, AgIn[PO₃(OH)]₂, has been synthesized using hydrothermal method. It crystallizes in the P2₁/c space group with the cell parameters a = 6.6400(2) Å, b = 14.6269(6) Å, c = 6.6616(4) Å, β = 95.681(5)°, V = 643.82(6) Å³, Z = 4. Its three-dimensional framework, built up of corner-sharing PO₃(OH) tetrahedra and InO₆ octahedra, presents intersecting tunnels running along <111> and [100] directions, in which the Ag⁺ cations are located. The presence of hydroxyl groups has been confirmed from IR spectroscopy studies and hydrogen atoms were located from the single crystal X-ray diffraction study. The structural relationships with the other compounds of general formula A^IM^III[PO₃(OH)]₂ are analyzed.     

Ce(H2O)(PO4)3/2(H3O)1/2(H2O)1/2, a second entry in the structural chemistry of cerium(IV) phosphates

A cerium(IV) phosphate has been prepared using precipitation methods and its structure has been solved by single crystal X-ray diffraction (R₁ = 0.0292 for 3092 reflections with I>2σ(I) and wR₂ = 0.0540). Ce(H₂O)(PO₄)_3/2(H₃O)_1/2(H₂O)_1/2 crystallises in the monoclinic space group C2/c (a = 15.7058(17) Å, b = 9.6261(9) Å, c = 10.1632(4) Å, ß = 121.623(7)°, and V = 1308.4 (2) Å³). Its structure is based on a negatively charged 3D framework, made of cerium atoms connected by PO₄ tetrahedra. There are two types of PO₄ units; one shares only corners with the cerium coordination polyhedra while the other one shares edges and corners. This structure also includes hydronium cations, to balance the framework charge, and water molecules. One special feature of this 3D framework is the formation of interconnected tunnels which extend along the c axis and contain the hydronium cations and the water molecules. This open framework and the presence of cationic species in the tunnels are in perfect agreement with the previously reported ion exchange properties.     

Double beryllium iodate dihydrates,M2Be(IO3)4·2H2O (M = K,NH4+, Rb): Preparation,X-ray powder diffraction and vibrational spectra

The solubilities in the three-component systems MIO₃–Be(IO₃)₂–H₂O (M = K, NH₄⁺, Rb, Cs) were studied at 25 °C by the method of isothermal decrease of supersaturation. It has been established that double salts, K₂Be(IO₃)₄·2H₂O, (NH₄)₂Be(IO₃)₄·2H₂O, and Rb₂Be(IO₃)₄·2H₂O, crystallize from the ternary solutions within wide concentration ranges. Both the X-ray powder diffraction and the spectroscopic studies (infrared and Raman) reveal that the title compounds are isostructural. They crystallize in the monoclinic space group P2/m with lattice parameters: K₂Be(IO₃)₄·2H₂O – a = 14.218(5) Å, b = 6.747(2) Å, c = 5.765(2) Å, β = 98.74(4)°, V = 546.6(2) Å³; (NH₄)₂Be(IO₃)₄·2H₂O – a = 14.414(4) Å, b = 6.838(2) Å, c = 5.947(2) Å, β = 99.52(4)°, V = 578.0(2) Å³; Rb₂Be(IO₃)₄·2H₂O – a = 14.423(4) Å, b = 6.867(2) Å, c = 5.743(3) Å, β = 98.15(3)°, V = 562.9(3) Å³.Infrared spectroscopic experiments show that comparatively strong hydrogen bonds are formed in the potassium and rubidium salts as deduced from the wavenumbers of ν_OD of matrix-isolated HDO molecules (isotopically dilute samples) owing to the strong Be–OH₂ interactions (synergetic effect). However, the IO₃⁻ ions in the ammonium compound are involved in hydrogen bonds with NH₄⁺ ions additionally to those with water molecules and as a result of these intermolecular interactions the proton acceptor strength of the iodate ions decreases (anti-cooperative effect), thus leading to the formation of weaker hydrogen bonds in this compound (bonds of moderate strength) as compared to those formed in the potassium and rubidium ones. The normal vibrations of other entities (IO₃⁻ ions and BeO₄ tetrahedra (skeleton vibrations)) are also discussed.     

Solvothermal synthesis and crystal structure of the Mo(VI)-bridged helical chain containing Mo2(V) dimers: (C4H12N2)2[(MoV2O4)(MoVIO4)(C2O4)2]·2H2O

A new molybdenum complex (C₄H₁₂N₂)₂[(Mo^V₂O₄)(Mo^VIO₄)(C₂O₄)₂]·2H₂O, was solvothermally synthesized and characterized by single-crystal X-ray diffraction. The structure of the compound consists of oxalate acid-coordinated mixed-valent [Mo^V₂O₄][Mo^VIO₄] helical chains and protonated piperazine cations. The helical chains are built up from the [Mo^V₂O₄] units and [Mo^VIO₄] tetrahedral. The central axis about helical chain is a 2-fold screw axis. The compound crystallizes in the space group P2₁/n of monoclinic system with a = 11.396(2) Å, b = 14.107(3) Å, c = 15.805(3) Å, β = 102.09(3)°, V = 2484.6(9) Å³, Z = 4. Other characterizations by elemental analysis, IR, and thermal analysis for this compound are also given.     

Synthesis and structure of a new scorpionate-dithio carboxyl oxovanadium complex and an organic dithio carboxyl compound

A new complex of oxovanadium(IV), V₂O₂[(HB(pz)₃)₂(pyrro)₂ (1) and a dimer-dithio carboxyl compound (C₅H₈NS₂)₂ (2) have been synthesized by the reaction of VOSO₄·nH₂O with NaHB(pz)₃ and pyrrolidine dithio carboxylic acid ammonium salt. They were characterized by element analysis, IR spectra, UV–vis spectra and X-ray diffraction. Structural analyses of 1 and 2 gave the following parameters: 1, triclinic, P-1, a = 7.732(4) Å, b = 14.285(8) Å, c = 17.802(9) Å, α = 101.314(8)°, β = 92.682(9)°, γ = 92.228(9)°, V = 1923.6(18) Å³, and Z = 4; 2, monoclinic, C2/c, a = 13.857(2) Å, b = 10.4213(18) Å, c = 9.436(2) Å, β = 97.099(2), V = 1352.1(4) Å³, and Z = 4. In complex 1, vanadium atom adopts a distorted tetragonal bipyramid structure, which is typical for oxovanadium(IV) complexes. Compound 2 is a dimer-dithio carboxyl compound with S–S bond. In addition, thermal analysis was performed for analyzing the stabilization of the complexes.     

Syntheses,structures and single-molecule magnetic behaviors of two dicubane Mn4 complexes

The reaction of MnX₂ · 4H₂O (X = Cl or Br) with 2,6-bis(hydroxymethyl)-4-methylphenol (H₃L) and NaOH in methanol solution yielded two tetranuclear manganese complexes, [Mn₄(HL)₄(MeOH)₄Cl₂] (1) and [Mn₄(HL)₄(MeOH)₄Br₂] (2). Both compounds crystallize in the monoclinic space group C₂/c with cell parameters: a = 26.0945(19) Å, b = 11.4999(8) Å, c = 21.2188(16) Å, β = 121.050(1)° and z = 4 for 1 · 2Et₂O; a = 25.8145(3) Å, b = 11.6734(2) Å, c = 21.3956(3) Å, β = 120.1277(6)° and z = 4 for 2 · 2Et₂O. Both complexes consist of a mixed-valence dicubane structure, which comprises two Mn^II and two Mn^III ions. Magnetic susceptibilities and magnetization of complexes 1 and 2 in the solid state indicate that two clusters have an S = 9 ground state. Frequency-dependent out-of-phase signals of alternating current magnetic susceptibilities were observed in the low temperature range (<3 K) for both complexes indicating a slow magnetic relaxation.     

Structure and magnetic properties of a novel copper diphosphonate with pillared layered structure:: Cu2(H2O)2{O3PCH2N(C2H4)2NCH2PO3}

Compound Cu₂(H₂O)₂{O₃PCH₂N(C₂H₄)₂NCH₂PO₃} (1) has a pillared layered structure in which the organic groups of N,N′-piperazinebis(methylenephosphonate) are sandwiched between the inorganic layers. Compared with other copper phosphonates with layered or pillared layered structures, the inorganic layer in 1 is unique in that each {CPO₃} tetrahedron is corner-shared with three {CuO₄N} square pyramids through three oxygen donors. Ferromagnetic interactions are mediated between the metal centers. Crystal data: Pbca, a=10.0830(16) Å, b=9.4517(15) Å, c=13.218(2) Å, V=1259.7(3) Å³, Z=4.     

Syntheses and crystal structures of new vanadium(IV) oxyphosphates M(VO)2(PO4)2 with M = Co,Ni

We have extended our research interest on titanium oxyphosphates (M^II(TiO)₂(PO₄)₂, with M^II = Mg, Fe, Co, Ni, Cu, Zn) to vanadium oxyphosphates M^II(V^IVO)₂(PO₄)₂ (M^II = Co, Ni). For each compound two phases, named α and β according to synthesis conditions, have been stabilized at room temperature, then characterized. The four crystal structures M(VO)₂(PO₄)₂ (α and β for M = Co, Ni) have been determined in monoclinic P2₁/c space group using X-ray single crystals diffraction data. Structure of the α phase is derived from the Li(TiO)(PO₄) (orthorhombic Pnma) and LiNi_0.50(TiO)₂(PO₄)₂ (monoclinic P2₁/c) types, with cell parameters: a = 6.310(1) Å, b = 7.273(1) Å, c = 7.432(1) Å, β = 90.43(1)° for M = Co, and a = 6.297(2) Å, b = 7.230(2) Å, c = 7.421(2) Å, β = 90.36(2)° for M = Ni. Structure of the β phase is derived from the Ni(TiO)₂(PO₄)₂-type (monoclinic P2₁/c) with cell parameters: a = 7.2742(2) Å, b = 7.2802(2) Å, c = 7.4550(2) Å, β = 120.171(2)° for M = Co, and a = 7.2691(2) Å, b = 7.2366(2) Å, c = 7.4453(2) Å, β = 120.231(2)° for M = Ni. All these structures consist of a three dimensional (3D) framework built up of infinite chains of tilted corner-sharing [VO₆] octahedra, cross-linked by corner-sharing [PO₄] tetrahedra. The M²⁺ ion (M = Co, Ni) is located in a triangular based antiprism which shares faces with two [VO₆] octahedra. Structural filiation is discussed based on a common structural unit, a sheet where divalent cations M²⁺ (M = Co, Ni) are inserted. A thermal study of the α ? β transition is also presented.