CN108129334B

CN108129334B - Single crystal of partially mono-substituted Keggin type polyacid and preparation method thereof

Info

Publication number: CN108129334B
Application number: CN201711266980.XA
Authority: CN
Inventors: 贺欢; 顾钊; 喻鑫; 郑英琦; 雷润
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2017-11-27
Filing date: 2017-11-27
Publication date: 2021-06-11
Anticipated expiration: 2037-11-27
Also published as: CN108129334A

Abstract

A single crystal of a partially monosubstituted Keggin type polyacid, the molecular formula is C ₂₄ Co _3.9 N ₁₈ O _40.6 SiW _11.1 H _80.6 , the crystal belongs to the monoclinic system, the space group is Pc, and the structural formula is [Co(NH ₂ C ₂ H ₄ NHC ₂ H ₄ NH ₂ ) ₂ ] ₃ · [SiW _11.1 Co _0.9 O ₃₉ ] · (OH) _0.6 · H ₂ O, unit cell parameters:

α=90°; β=126.457(2)°; γ=90°. Z=2, R1=0.0560, wR2=0.0946. In this crystal, both Co and W are six-coordinated, and Si is four-coordinated. One metal site in an asymmetric unit of the unit cell is jointly occupied by Co and W, with the proportions of 90% and 10%, respectively. There are 1 Si, 11.1 W, and 0.9 Co atoms in the asymmetric unit, which are bridged by oxygen atoms to form a Keggin-type polyacid structure, which has 3 complex polymers and a free water outside the polyacid structure. molecule, this _complex _consists of _{NH2C2H4NHC2H4NH2} and _Co _atoms _.

Description

Single crystal of partially mono-substituted Keggin type polyacid and preparation method thereof

Technical Field

The invention belongs to the technical field of inorganic chemistry polyoxometalate clusters, and particularly relates to a partially mono-substituted polyacid crystal containing a metal complex as a counter cation and a preparation method thereof.

Background

Metal-oxygen Clusters (Metal-Oxide Clusters), also known as Polyoxometalates (POMs), are highly symmetric multi-core inorganic Clusters formed by the attachment of early transition Metal ions through oxygen atoms. The framework elements are usually high valence ions of some early transition metals, such as Mo (VI), W (VI), V (V), Nb (V), Ta (V), etc. The basic unit of the metal ion M is mainly MO₆XO composed of octahedron and non-metal ion or main group metal ion X₄Tetrahedrons, polyhedrons are connected in a corner-sharing, edge-sharing or coplanar manner to form metal-oxygen cluster anions with various structures.

The development of metal-oxygen cluster chemistry has been in recent 200 years and is an important research area in inorganic chemistry. In 1826, the first metal-oxygen cluster-12-molybdophosphoric acid (NH)₄)₃PMo₁₂O₄₀·nH₂O was discovered, but in 1864 scientists began to truly study it: scientists successfully synthesize silicotungstic acid and accurately determine the composition by a chemical analysis method, determine the silicon-tungsten ratio of 1:12, and also find that the compound has geometric isomerism. In 1908, Miolati, Italy confirmed that phosphomolybdic acid contains 7 protons and its molecular formula was H₇P(Mo₂O₇)₆(ii) a In 1913, Rosenheim, Germany synthesized phosphomolybdic acid by extraction with diethyl ether, to which guanidinium salt (CH) was added₃H₅)₂H₂CO₃The corresponding guanidine phosphomolybdate is prepared. In 1929, the metal-oxygen cluster "basket-flower" type structure proposed by Pauling in the United states was assumed: silicotungstic acid is SiO₄Tetrahedron (and phosphotungstic acid centered at PO)₄Tetrahedron), 12 WO₆Octahedral into cage-like structures SiO₄(or PO)₄) In which the tetrahedron is enclosed. In 1934, Keggin, a England physicist, performed X-ray powder diffraction on H₃PW₁₂O₄₀·5H₂O tests and proposes a famous Keggin structural model. In 1936 Bradley further tested H by means of X-ray powder diffraction₃PW₁₂O₄₀·29H₂And O, further verifying the Keggin structure. In 1974, the correctness of the Keggin structure was finally confirmed by using a single crystal diffraction technology. In 1937 Anderson in England proposed six MOs according to Pauling's principle₆The ring structure formed by octahedral coterminous junctions was determined by single crystal diffraction technique by Evans in England in 1948 (NH)₄)₆[TeMo₆O₂₄]·7H₂O and K₆[TeMo₆O₂₄]·7H₂The molecular structure of O is also called Anderson-Evans structure. In 1952, Lindqvist, Sweden, performed on Na₇H[Nb₆O₁₉]·16H₂And O, a Lindqvist model is proposed. In 1953, Dawson determined K by using single crystal X-ray technology₆[P₂W₁₈O₆₂]·14H₂The position of the tungsten atom in O, this structure is called Dawson structure.

The cluster compound is used as a novel high-efficiency catalyst to realize application in industry: the industrialization of the 12-silicotungstic acid catalyzed propylene hydration reaction is realized in 1972; in 1982, 12-phosphomolybdic acid was used to catalyze the gas phase oxidation of methacrolein to methacrylic acid; in 1984, 12-phosphomolybdic acid was used to catalyze the hydration of isobutylene to make tert-butyl alcohol; in 1986, 8 industrial projects such as polyoxyl tetra-methyl glycol prepared by THF catalyzed by 12-phosphotungstic acid were put into production successively, and five metal-oxygen cluster chemical research centers appeared in the world, namely United states, France, Japan, China and Russia. In the development trend, the metal-oxygen cluster chemistry has a trend of fusing with the intersection of various disciplines. Especially, the organic-inorganic hybrid metal-oxygen cluster material has the characteristics of both organic components and inorganic components, has strong structural plasticity, high stability and excellent performance, and can be widely applied to the fields of light, electricity, magnetism, adsorption, catalysis, molecular recognition, biological conduction and the like.

In the last 10 years, transition metal substituted/rare earth metal substituted polyacids have also become a new growth point for polyacid chemistry. Different substituted metals and structures bring a plurality of excellent properties to the product. However, there is no systematic study in this field. Because the regularity of inorganic synthesis is not strong. Homologues, isomorphic compounds are extremely difficult to synthesize, such as: the 3-site-deficient polyacid substituted by 6-core nickel is common, but a similar structure cannot be obtained by Co, Zn, Cu and Cd, and the 3-site-deficient polyacid substituted by 8-core copper is reported, but other transition metals cannot obtain a similar structure although the structure is similar and the performance is similar. At present, only between adjacent rare earth elements, due to the lanthanide contraction effect, compounds with similar structures can be obtained, and the compounds are often limited to 3-4 rare earth elements which are closely adjacent on the periodic table of the elements. And because of different rare earth elements, the chemical properties, optical properties and magnetic properties of several compounds with similar structures are also quite different.

Disclosure of Invention

The invention aims to disclose a mono-substituted keggin type polyacid crystal containing 3 cobalt complexes as counter cations and a preparation method thereof, wherein the structure of the crystal is as follows: [ Co (NH)₂C₂H₄NHC₂H₄NH₂)₂]₃·[SiW_11.1Co_0.9O₃₉]·(OH)_0.6·H₂O, molecular formula C₂₄Co_3.9N₁₈O_40.6SiW_11.1H_80.6The structural formula is shown in the attached figure 1 in the specification.

The crystal belongs to a monoclinic system, a space group Pc and the unit cell parameters are as follows: unit cell parameters:

α＝90°；β＝126.457(2)°；

γ＝90°.Z＝2，R1＝0.0560，wR2＝0.0946。

all atomic coordinates except H are as follows: the unit of the coordinates is

Wherein C is_O(1) And the W (12) atom together occupy the same position, and the Co atom partially replaces the SiW of the classical keggin structure₁₂O₄₀One W atom in (c). The proportion of Co was 90% and the proportion of W was 10%. The reason why two metal atoms appear at the same position is that the structural unit represents not one molecule but each molecular structure in the entire crystal in which the position has both Co and W in a ratio of 9:1. all W and Co are hexa-coordinated, and 6O atoms connected to the periphery form the structure with a quadrangular bipyramid. Si is four-coordinate, and forms a tetrahedral structure with 4 surrounding O atoms, and the polyhedral structures form a cage cluster structure containing one Si and 12 transition metals by sharing the O atoms. Wherein Si atoms are positioned at the center of the cage cluster, 3 transition metal clusters of 12 are in a group to form small clusters of 4 plane triangles, and the four small clusters are covered on SiO from four directions like four vertexes of a regular tetrahedron₄Around the cage cluster, a 3-Co atom coordination polymer is liberated, each Co atom and two NH atoms₂C₂H₄NHC₂H₄NH₂Molecules, coordinately linked through three N atoms. The three free Co are also hexa-coordinated, with a tetragonal bipyramid structure.

There is also a free water molecule in the structure and 0.6 OH in the compound^-. But the spatial position cannot be accurately calibrated due to disorder in the crystal structure. The molecular weight of the compound was about 3569.75 g/mol.

The powder diffraction peak position and intensity of the compound are shown in the following table

Peak position and peak intensity of X-ray powder diffraction

Advantageous effects

By strictly controlling the types and the proportion of the raw materials, the pH value and the temperature of the reaction, the invention obtains the single crystal of the Keggin polyacid with partially mono-substituted Co, and the yield of the Keggin polyacid can reach 79 percent.

Drawings

FIG. 1 shows a cluster crystal [ Co (NH) ] of the present invention₂C₂H₄NHC₂H₄NH₂)₂]₃·[SiW_11.1Co_0.9O₃₉](OH)_0.6·H₂The structural formula of O. Wherein Co1 and W12 together occupy the same position in a 9:1 ratio.

Detailed Description

Will [ SiW₉O₃₄]^10-And CoCl₂Dissolving in distilled water, adding NH₂C₂H₄NHC₂H₄NH₂Adding weak base to regulate pH value, and heating in sealed container to react. The reaction time is 7-14 days. The reaction is synthesized by a hydrothermal method, and reactants are placed in a stainless steel reaction kettle with a polytetrafluoroethylene lining and are sealed and heated. The reaction temperature is 80-120 ℃. [ SiW)₉O₃₄]^10-And CoCl₂Are each K₁₀[SiW₉O₃₄]·25H₂O and CoCl₂·6H₂O; the weak base for adjusting the pH value is K₂CO₃。

Example 1

Will K₁₀[SiW₉O₃₄]·25H₂O (0.306g,0.10mmol) and CoCl₂·6H₂O (0.238g,1.00mmol) was dissolved in distilled water (5mL), and NH was added dropwise thereto successively under stirring₂C₂H₄NHC₂H₄NH₂(0.1mL,0.93mmol) and K₂CO₃(0.05mL,2.0mol/L) and the pH of the solution was 8.5. The resulting mixture was stirred at room temperature for 3 hours, then the mixture was charged into a 20mL stainless steel reaction vessel with a Teflon liner, sealed, reacted at 110 ℃ for 10 days, cooled to room temperature to give the red single crystal of the present invention in bulk, which was washed with water and dried at room temperature, and weighed to give a yield of about 79% (K)₁₀[SiW₉O₃₄]·25H₂O calculation).

Example 2

Will K₁₀[SiW₉O₃₄]·25H₂O (0.306g,0.10mmol) and CoCl₂·6H₂O (0.238g,1.00mmol) was dissolved in distilled water (5mL), and NH was added dropwise thereto successively under stirring₂C₂H₄NHC₂H₄NH₂(0.1mL,0.93mmol) and K₂CO₃(0.05mL,2.0mol/L) and the pH of the solution was 8.5. The resulting mixture was stirred at room temperature for 3 hours, then the mixture was charged into a 20mL stainless steel reaction vessel with a Teflon liner, sealed, reacted at 100 ℃ for 10 days, cooled to room temperature to give the red single crystal of the invention in bulk, which was washed with water and dried at room temperature to give a yield of about 40% (K) and weighed₁₀[SiW₉O₃₄]·25H₂O calculation).

Example 3

Will K₁₀[SiW₉O₃₄]·25H₂O (0.306g,0.10mmol) and CoCl₂·6H₂O (0.238g,1.00mmol) was dissolved in distilled water (5mL), and NH was added dropwise with stirring₂C₂H₄NHC₂H₄NH₂(0.1mL,0.93mmol) of the resulting mixture to a solution pH of 7.5. Stirring for 3 hours at room temperature, then putting the mixture into a 20mL stainless steel reaction kettle with a polytetrafluoroethylene lining, sealing, reacting for 10 days at 110 ℃, cooling to room temperature to obtain the massive red single crystal, washing the red single crystal with poor crystal quality and drying at room temperature, weighing, and obtaining the yield of about 20% (K)₁₀[SiW₉O₃₄]·25H₂O calculation).

Example 4

Will K₁₀[SiW₉O₃₄]·25H₂O (0.306g,0.10mmol) and CoCl₂·6H₂O (0.238g,1.00mmol) was dissolved in distilled water (5mL), and NH was added dropwise thereto successively under stirring₂C₂H₄NHC₂H₄NH₂(0.1mL,0.93mmol) and K₂CO₃(0.1mL,2.0mol/L) and the pH of the solution was 9. The resulting mixture was stirred at room temperature for 3 hours, then the mixture was charged into a 20mL stainless steel reaction vessel with a Teflon liner, sealed, reacted at 110 ℃ for 10 days, cooled to room temperature to give the red single crystal of the present invention in bulk, which was washed with water and dried at room temperature, and weighed to give a yield of about 15% (K)₁₀[SiW₉O₃₄]·25H₂O calculation).

Comparative example 1:

with the same molar ratio of NaWO₄·2H₂O and Na₂SiO₃·9H₂O instead of K₁₀[SiW₉O₃₄]·25H₂O (0.306g,0.10 mmol). Other reaction conditions were not changed, and a product having the same structure as in example 1 was not obtained.

Comparative example 2:

with NaWO₄·2H₂O and Na₂SiO₃·9H₂O instead of K₁₀[SiW₉O₃₄]·25H₂O (0.306g,0.10mmol) and adjusting the ratio range, NaWO₄·2H₂O：Na₂SiO₃·9H₂O：CoCl₂·6H₂O：NH₂C₂H₄NHC₂H₄NH₂：H₂When O is 1:0.1:1:10:500, other reaction conditions are not satisfiedAlternatively, a product having the same structure as in example 1 was not obtained.

Comparative example 3:

on the basis of comparative example 2, the reaction conditions were further adjusted to perform permutation and combination according to the following table. No product having the same structure as in example 1 was obtained. The following table is used to perform the experiments in an orthogonal manner, not just in the transverse or longitudinal direction.

Comparative example 4:

the hydrochlorides and carbonates of transition metals Cr, Mn, Fe, Ni, Cu and Zn are selected to replace the Co salt of the application, and experiments are carried out according to the reaction conditions of the example 1, and all the products have the same structure as the example 1.

Further, we found that the reaction time and reaction temperature had a large influence on the results of the experiment, and that the reaction time was more than 120 ℃ or less than 80 ℃ or less than 7 days, and a product having the same structure as in example 1 could not be obtained.

Single crystal testing: the single-crystal product obtained in example 1 was further characterized by the following procedure:

structural determination of the compounds: selecting a single crystal with a proper size, placing the single crystal on a Bruker SMART APEX II CCD single crystal diffractometer, using Mo Kalpha rays monochromated by graphite as a light source, and collecting diffraction data in an omega/2 theta scanning mode at the temperature of 291(2) K. Data recovery was performed using the SAINT program and absorbance correction was performed using the SADABS program. The structure of the compound is solved by a direct method, and the coordinate of a non-hydrogen atom and the anisotropic temperature factor are refined by a full matrix least square method. The structure analysis adopts SHELXS-97, and the structure refinement adopts SHELXL-97.

The above examples are merely illustrative of the present invention, and other embodiments of the present invention are possible. However, all the technical solutions formed by equivalent alternatives or equivalent modifications fall within the protection scope of the present invention.

Claims

1. a preparation method of a partial monosubstituted Keggin type polyacid crystal, is characterized in that: the molecular formula of described partial monosubstituted Keggin type polyacid crystal is C ₂₄ Co _3.9 N ₁₈ O _40.6 SiW _11.1 H _80.6 ; the product is a single crystal , the crystal belongs to monoclinic system, space group Pc, and the structural formula is [Co(NH ₂ C ₂ H ₄ NHC ₂ H ₄ NH ₂ ) ₂ ] ₃ ·[SiW _11.1 Co _0.9 O ₃₉ ]·(OH) _0.6 ·H ₂ O;

Both Co and W are six-coordinated, and Si is four-coordinated. One metal site in an asymmetric unit of the unit cell is co-occupied by Co and W, and the proportions are 90% and 10%, respectively. The unit cell asymmetric unit It has 1 Si, 11.1 W, and 0.9 Co atoms in it, which are bridged by oxygen atoms to form a Keggin-type polyacid structure. There are 3 complex polymers and a free water molecule outside the polyacid structure. The complex consists of NH ₂ C ₂ H ₄ NHC ₂ H ₄ NH ₂ and Co atoms;

The preparation method includes: dissolving [SiW ₉ O ₃₄ ] ^10- and CoCl ₂ in distilled water, adding NH ₂ C ₂ H ₄ NHC ₂ H ₄ NH ₂ , adding a weak base to adjust the pH value, and heating the reaction in a closed container;

The reaction time is 7 to 14 days; the reaction is synthesized by hydrothermal method, and the reactant is placed in a stainless steel reaction kettle with a polytetrafluoroethylene lining, and sealed and heated;

Add weak base to adjust pH to 8-8.5;

K ₁₀ [SiW ₉ O ₃₄ ]·25H ₂ O: CoCl ₂ ·6H ₂ O: NH ₂ C ₂ H ₄ NHC ₂ H ₄ NH ₂ : H ₂ O=0.1:1:0.93:250～350;

The reaction temperature is 105°C-110°C.

2. The preparation method according to claim 1, wherein: unit cell parameters: a=10.8937(3) angstroms; b=23.1012(9) angstroms; c=16.5459(5) angstroms; α=90°; β =126.457(2)°; γ=90°, Z=2, R1=0.0560, wR2=0.0946.

3. The preparation method according to claim 1, characterized in that: [SiW ₉ O ₃₄ ] ^10- and CoCl ₂ are respectively K ₁₀ [SiW ₉ O ₃₄ ]·25H ₂ O and CoCl ₂ ·6H ₂ O; adjusting The weak base for pH is K ₂ CO ₃ .