Synthesis and complex study of the crystal hydrate ZnZr2F10?6H2O

Synthesis and complex study of the crystal hydrate ZnZr

2

F

10∙6H O

2

E.I. Voit, N.A. Didenko, A.V. Gerasimenko, A.B. Slobodyuk

Institute of Chemistry FEBRAS, 159, Pr. 100-letiyaVladivostoka, Vladivostok, 690022, Russia

*

Corresponding author: Fax: +7 (423) 2311889

E-mail address: evoit@ich.dvo.ru (E.I. Voit)

Graphical abstract

Highlights



New crystal hydrate of the composition ZnZr

2

F

10∙6H O has been synthesized.

2



The crystal structure of the compound was determined by the X-ray method.

2



2+

The crystal structure is built of flat anion layers _



ZrF₅



and [Zn(H

2

O) ] cations.

6



The complex cations and anions are linked by hydrogen bonds.

The IR, Raman and NMR spectroscopy data for the compound and products of its

dehydration were analyzed.

Abstract. The synthesis and study of the structure and properties (by methods of X-

1

19

ray structural analysis, DTA, IR, Raman, and H, F NMR, including F MAS NMR) of a

new crystal hydrate of the composition ZnZr O (1) have been performed.

2

F10∙6H

2

The compound 1 crystallizes in the monoclinic system with the following unit cell

parameters: a=6.5628(2), b=10.2031(4), c=9.0965(4) Å, β=100.532(1)°, sp.gr. C2/m, Z=2.

The crystal structure is built of flat cross-linked anion layers of the composition

2

2

O)

]²⁺cations. The complex cations and anions are



Zr F



and octahedral [Zn(H

2

6



2

10

linked in the structure into a three-dimensional network by O–H···F and O–H···O

hydrogen bonds.

It has been established that decomposition of 1 in temperature range 50-850°C in air

proceeds stepwise through the following stages: ZnZr

ZnZr O → ZnZr OF with formation of the mixture of the final products ZnO and

ZrO . The vibrational and NMR spectroscopy data for the initial compound and

2

F10∙6H

2

O → ZnZr

2

F

10∙4H O →

2

F10∙2H

2

8

2

intermediate products of its decomposition have been obtained, systematized, and

summarized.

Keywords: fluoridozirconates; hydrates; zinc; crystal structure; hydrogen bonds.

1

.

Introduction

Complex zirconium fluorides with the stoichiometric ratio of F/Zr=5 were substantially less

studied among other numerous fluorine-containing compounds of zirconium in terms of revealing

the ‘structure – property’ interrelation, as opposed to hexafluoridozirconates with the homo- and

heterovalent cation sublattice [1]. Crystal structures of the layered pentafluoridozirconates known

by the date exhibited, in most cases (12 of 14 structures), the octo-coordination of zirconium

polyhedra [2].

Analysis of crystal structures of pentafluoridozirconates with cations of various nature and

+

2+

size – hydroxonium (H

3

O ), monovalent (Tl , NH

4

, K ), divalent (Ba ) ions, protonated organic

CH ) enabled one to discover a series

molecules (enH

of regularities.

2

, (gly)H, (ala)H), and alkylammonium (NH

3

One of them consisted in a similar structure of anion layers in the structures with outer-sphere

cations of large size, in which cation-anion interactions were supplemented by hydrogen bonds. A

series of isotypical compounds belong to this group: (H

cation sublattice), [enH ]Zr O, [NH Me]ZrF ∙0.5H

(gly)H]ZrF ∙2H O [3-6]. In these structures, octa-coordinated zirconium polyhedra are linked by

three common edges, thus assembling hexanuclear cycles and forming polymer layers of _

3

O)ZrF

5

∙nH

2

O (n=1, 2; with aqueous-

2

F10∙H

2

3

5

2

O, [meamH]

2

(Zr O, and

2

F

10)∙H

2

[

5

2





ZrF₅



.

However, in pentafluoridozirconates with mono- or divalent outer-sphere cations such as Tl⁺,

2

2

+

2+

NH

4

, Ba , infinite layers of _



Zr F



are realized, in which coordination [ZrF ] polyhedra

8

2 10

share a common edge and four vertices with other polyhedra (TlZrF

5

, NH

7-9]). Other type of bonding (by two edges and two vertices) is realized in the structure of KZrF

10]. Therefore, in the structures with cations of varied sizes with high CN (10-14), to saturate

bonds), variation of a ratio of

bridging bonds (edge/vertex bonds) in the anion layer occurred. Here, the layered structural

pattern, in which each [ZrF ] polyhedron corresponds to six bridging and two terminal F atoms,

4

ZrF

5

, BaZr

2

F

10∙2H O

2

[

5

their coordination capacity by M-F bonds (or M-F and M-OH

2

8

persisted, while the polymerization degree of the anion sublattice (ratio of the number of bridging

F atoms to that of terminal ones) remained equal to three.

I

Pentafluoridozirconates M ZrF

known both in a nonaqueous form and in the form of crystal hydrates obtained from solutions.

Monohydrates of pentafluoridozirconates were typical for NH , K, Na, Rb, Cs, and Tl [11]. A

crystal hydrate having the composition NH ZrF ∙0.75H O was synthesized with an ammonium

cation and its structure was investigated [12]. The indicated compounds belong to mixed-ligand

complex compounds, where a central atom is coordinated, beside F-ligands, by H O molecules.

The authors of [13] investigated the effect of the hydrate number on the structure, thermal

properties, and the character of ionic mobility in NH ZrF ∙nH O (n=1, 0.75) crystal hydrates and

5

with monovalent cations (M – Na, K, Rb, Cs, Tl, NH

4

) were

4

5

2

4

5

2

the dehydration product NH

4

ZrF

5

by means of the vibrational, NMR-spectroscopy and DTA.

+

⁺) monohydrates and their

Comparison of the structures of MZrF

5

∙H

2

O (M – K , NH

4

nonaqueous analogs allows concluding that at the ratio F/Zr=5 in the complex anion an additional

coordination of zirconium by molecules of H O results in the transition from infinite layers of

2



1





ZrF₅



to _



ZrF (H O)



polymer chains. Types of Zr coordination polyhedra and ways of their



5

2

bonding are also different.

By the date, there are very few structural data on pentafluoridozirconates with divalent

II

cations M Zr

pentafluoridozirconate β-BaZr

works. Two modifications of BaZr

phase was not established. A high-temperature monoclinic β-phase was built from [Zr

2

F

10 and crystal hydrates M Zr

10 and crystal hydrate BaZr

10 are known by the date. The structure of the triclinic α-

12] dimers,

2

F

10∙nH

2

O. The structural data on nonaqueous

2

F

2

F10∙2H

2

O can be found in published

2

F

2

F

which consists of two pentagonal bipyramids (CN of Zr is 7) bonded through a common edge. The

dimer groups are linked by common vertices into infinite zigzag chains forming doubled layers.

2

+

Ba cations are located between them [14].

2

2

Anion layers of _



Zr₂F₁₀



serve as a base for the crystal lattice of BaZr

2

F

10∙2H

O [9]. Ba²⁺

2

cations and water molecules link the neighboring layers by ionic interaction and stabilize the

structure through hydrogen bonds. H O molecules in the cation sublattice of BaZr O are

nonequivalent: one of them is terminal, while another one is bridging. Dehydration of the

2

F10∙2H

2

compound proceeds stepwise. First, within the range ~70-150°C, one water molecule splits off

forming BaZr O, whose structure is similar to the initial one and to that of TlZrF . At the

2

F10∙H

2

5

temperature above 150°C, the second water molecule splits off, and the crystal lattice of the

nonaqueous phase destructs. In the X-ray pattern of the product heated up to 240°C, reflections of

ZrF

metal ion) characterized by a large ionic radius, high CN, and ion-dipole nature of Ba –H

interaction serves as a double-charged outer-sphere cation in crystal hydrates of

pentafluoridozirconates, then the variation of the hydration degree of a cation in BaZr

n=2, 1) insignificantly affects the structural pattern of the complex anion and the structure in

general.

4

and a phase of unknown composition were observed [9]. Therefore, if Ba²⁺(nontransition

2

+

2

O

2

F

10∙nH O

2

(

Up to present, there are no structural data on highly aqueous crystal hydrates of

pentafluoridozirconates with divalent d-transition elements. There is a reference found on the

formation of Cd(ZrF

Also, at investigation of the phase formation in the ZrO

ZnZr O and NiZr O (n=9, 7) systems were isolated and their IR-spectra were

5

)

2

∙6H

2

O [15] and the X-ray data on CuZr

2

F10∙6H

2

O (ICDD: N 00-048-1658).

2

-H

2

SO

4

-HF-Zn(NO (NiCl )-H O,

3

)

2

F10∙7H

2

F10∙nH

2

obtained [16, 17]. However, the effect of the hydration number on the structural organization was

not investigated in detail yet. The option of synthesizing a nonaqueous compound of the

II

composition M Zr

2

F10 via thermal dehydration of a low-aqueous crystal hydrate was not revealed.

The objective of the present study is to investigate the effect of the hydration number on the

structure of the cation and anion sublattices in a series of ZnZr O (n=6, 4, 2) compounds

2

F10∙nH

2

and their thermal stability. The body of the obtained data allows its comparison with the research

results on the effect of the hydration number on the structural transformation during transition of

ZnZrF

6

∙6H O to the nonaqueous compound through intermediate hydrate phases [18].

2

. Results and Discussion

2

.1. Crystal structure

The compound 1 crystallizes in the monoclinic system (sp. gr. C2/m, Z=2). Interatomic

distances in the structure of 1 are provided in Table 1.

The crystal structure of 1 appears to be similar to the structures of (H

O)ZrF ·2H O, (C )Zr O, (CH NH )ZrF ·0.5H O, (H NCH COOH)ZrF

COOH)ZrF

3

O)ZrF

5

·H

2

O,

(

H

3

5

2

H

10

N

2

F10·H

2

3

5

2

3

2

5

·2H

2

and (H

3

N(CH

2

)

2

5

[3, 4, 5, 19]. Its base consists of anion layers having the composition

O)

]²⁺cations

2

2



Zr F



parallel to the plane (001) and layers of complex octahedral [Zn(H

2

6



2

10

(Fig.1). The coordination polyhedron of Zr atom is represented by a trigonal dodecahedron

(hereinafter dodecahedron), which shares three edges with neighboring Zr-polyhedra (Fig. 2).

Zirconium atoms form hexanuclear cycles in the structure, in which the edge-bridging atoms

F(2)…F(2)ⁱ^vand F(2) …F(2) are located in the plane of zirconium layers, whereas the

i

iii

ii

F(1)…F(1) edge is perpendicular to the layer plane. The chains of Zr-polyhedra linked by the

iv

i

iii

F(2)…F(2) and F(2) …F(2) edges extending along the direction [100] in the layer can also be

ii

distinguished. The chains are linked to each other through the F(1)…F(1) edges. The interatomic

Zr…Zr distances in the chains are equal (3.594(3) Å) and shorter than between the chains

(3.6970(8) Å) (Table 1).

The layer formed by hexaaquacomplex [Zn(H

2

O)

]²⁺cations is linked to the anion

6

fluoridozirconate layers by hydrogen bonds of H

2

O molecules (Table 2, Fig. 3). Among three

bonds of this type, two bonds with the terminal fluorine F(3) atoms exhibit close length values of

2

.773(2) and 2.760(2) Å, while the length of the third bond with bridging F(1) atom is shorter –

x

.669(6) Å. There is only one interatomic distance O(3)···O(3) inside the aqua-cation layer

which is equal to 2.883(12) Å that can correspond to the O–H···O hydrogen bond (Fig. 3). We

suppose that the hydrogen atom linked to the H O(3) and not localized by us participates in this

2

hydrogen bond, and this atom is most likely disordered about the crystallographic plane m, on

which O(3), H(3) and Zn(1) atoms are located. The anion and cation layers are linked into a

three-dimensional network by a system of hydrogen bonds and ionic interaction (Fig. S1).

2

.2. Thermal analysis

Dehydration of the compound 1 proceeds stepwise in three stages within the wide

temperature range of 50-400°C (Fig. S2). In the range 50-120°C (endo-effect extremum at

9

6

0°C), the split-off of two water molecules occurres. Here, the weight loss is 6.7 % (∆mcalc

=

.61 %). As a result, new phase ZnZr O is formed: according to the powder X-ray

2

F10∙4H

2

diffraction (XRD) data, it has a characteristic set of reflections and their relative intensity (Fig.

S3). Heating up above 120°C leads to dehydration of tetrahydrate, which corresponds to the

endo-effect at 140°C. Total weight loss at 240°C is 13.3 %.

It is worth mentioning that the weight change at the second stage of decomposition of 1 is

followed by well-expressed overcooling effect on the temperature curve, which is related to the

simultaneous processes of dehydration and lattice rearrangement upon the transition

ZnZr

2

F10∙4H

2

O → ZnZr

2

F10∙2H

2

O.

Accordingly, as a result of successive dehydration of ZnZr

2

F

10∙6H O at 230-240°C, a new

2

compound of two-water hydrate is formed (Fig. S3). The third stage of decomposition is

characterized by initially slow and above 270°C intensive weight loss constituting 23.1 % at

3

30°C and 24.1% at 400°C. An admixture of dihydrate is still observed in the XRD patterns of

sample heated up to 330°C. At this stage, the mass loss exceeds the calculated value upon

removal of six water molecules per formula unit of 1 (∆mcalc = 19.82 %). This is probably a

consequence of the simultaneous occurrence of dehydration and pyrohydrolysis processes at the

stage of dewatering of the dihydrate.

The experimental weight loss at 400°C could correspond, in theory, to isolation of the

mixture 5H

of a product having total composition ZnZr

phase formed upon heating up to 400°C exhibits a cubic symmetry (sp. gr. Fm3m), since its

pattern coincides with that of the cubic modification of MgZr OF (sp.gr. Fm3m; a=7.996 Å)

20]. In addition, the diffractogram of ZnZr O (at 400°C) contains the additional lines of

small intensity corresponding to the Zr 10 oxyfluoride, which forms as a result of the

pyrohydrolysis of the ZnZr OF . Zr 10 content increases with increase of the temperature of

heating (Fig. S4). Oxofluoridozirconate MgZr OF [20] crystallizes in the NaSbF structural type

21]. The framework structure of MgZr OF is built of the vertex-bonded octahedra Mg(O/F)

and Zr(O/F) : here, some of Zr positions are occupied by Mg, while some fluorine atoms are

substituted by oxygen. Oxofluoridozirconate ZnZr OF formed as a result of dehydration and

pyrohydrolysis of ZnZr O, presumably, have a similar structure. Therefore, it is

impossible to receive a nonaqueous phase of the composition of ZnZr 10 under dehydration of a

2

O + 2HF (∆mcalc = 23.85 % relative to ZnZr

2

F

10·6H

2

O) with predominant formation

2

OF . According to the XRD patterns (Fig. S4), the

8

2

8

[

2

F

10·6H

2

7

9

O F

2

8

7

9

O F

2

8

6

[

2

8

6

2

8

2

F10∙2H

2

F

lower crystal hydrate, since some of the fluorine atoms are substituted by oxygen atoms as a

result of pyrohydrolysis. This is confirmed by the IR-spectrum of the product heated up to

4

00°C.

Pyrohydrolysis intensity of the cubic oxofluoride phase at temperatures above 420°C

increases due to interaction with air moisture. According to the XRD patterns of the sample

heated up to 500°C, a mixture of Zr 10 and ZnF is formed as a result of partial

decomposition of ZnZr OF (Fig. S4). ZnO (hexagonal) and ZrO (monoclinic) are the final

products of decomposition of 1 at 850°C. Total weight loss is 40.0 % (∆mcalc= 40.00 %).

7

O

9

F

2

8

2

.3. IR and Raman spectroscopy

The methods of vibrational spectroscopy allow one to obtain additional information about

the structure of 1 and its decomposition products. Observation of changes of the bands in the IR

absorption spectra brings information on the state of water in crystal hydrates. Figures 4, 5 show

the IR and Raman spectra of hexahydrate and the products of its heating up to 110 and 200C.

ZnZr

2

F

10∙6H

O. The complicated shape of band in the region of 3700–3100 cm^-¹

2

corroborates the presence of expanded network of H-bonds with different energies in the

structure of 1 (Fig. 1, Table 2). It is difficult to identify the asymmetric (ν

components of O-H stretching bonds of water molecules of the Zn(H

O) ²⁺

obtained for Zn(H O) 12) [22].

In the spectra of 1 two sets of bands with maxima at ~3562 and 3395 cm in the range of

3

) and symmetric (ν

1

)

2

6

cation, as was

2

6

(B12F

-1

stretching vibrations (νO-H) and at 1647 and 1614 cm of bending vibrations (δH–O–H) of water

2

+

molecules of the Zn(H

2

O)

and ~837 cm librational bands relate to vibrations of H

O(3)–H∙∙∙F(1) (2.669 Å) hydrogen bonds. Another group of bands at ~3562, 1614 cm^-¹

corresponds to vibrations of H O(1) and H O(2) molecules with longer O(1,2)–H∙∙∙F(3) (2.776

6

cation are observed (Fig. 4a). It is assumed that the ~3395, 1647,

-1

2

O(3) molecules involved in strong

2

and 2.760 Å) hydrogen bonds (Table 2). The existence of O(3)–H∙∙∙O(3) (2.883 Å) bonds in the

structure 1 additionally complicates the stretching vibration band.

-1

The low-intensive band with a maximum at ~3200 cm , which was observed in all the

spectra of ZnZr O (n=6, 4, 2), corresponds to an overtone of the bending vibrations (2ν

23].

Additional information on the structure of the fluoridoziconate anion can be obtained by

2

F10∙nH

2

)

[

-1

examining the vibrational spectra below 600 cm [24]. The anion layers in 1 are built just like in

the structure of H OZrF ∙2H O [3], and, as a consequence, their vibrational spectra are similar

Fig. 5a). In the IR-spectrum of 1, the band at 540 cm corresponds to asymmetric stretching

3

5

2

-1

(

-1

vibrations of the terminal Zr-F bonds, while the band at 398 cm – to asymmetric vibrations

with predominant contribution of the bridging Zr-F-Zr bonds (Table 3). In the Raman spectrum,

-1

the totally symmetric analogs of these bands with the maxima at 546 and 370 cm are active.

-1

The bands at ~252 and 211 cm correspond to the bending vibrations of the [ZrF ] group. The

8

-1

presence of a band at 177 cm is typical for the polymerized anion sublattices [25], and,

according to [26], it corresponds to lattice modes related with rotational and translational

motions of Zr polyhedra.

Of special interest are both the assessment of structural changes of complex anion and cation

and the effect of identical cations on hydrogen bond system in the series of [Zn(H

2

O)

6

]

2

(ZrF ) –

8

Zn(H O) (ZrF ) – Zn(H O) (Zr 10) crystalline hydrates (Table S1).

2

6

2

6

2

F

The structures of [Zn(H

isolated monomeric complex anions with Zr CN 8 and 6, respectively. Structural nonequivalence

was found in anionic (Zr1 and Zr2) and cationic sublattices of [Zn(H O) (ZrF ), in contrast to

Zn(H O) (ZrF ). The Zn-O bond lengths in [Zn(H O) (ZrF ) are in the ranges of 2.0367-

.1638, 2.0506-2.1258 and 2.0629-2.1119 Å for three nonequivalent Zn1, Zn2, Zn3 atoms. Thus,

in the structure of [Zn(H O) (ZrF ) the H-bonds system is the most developed: the existence of

2

O)

6

]

2

(ZrF

8

) [27] and Zn(H

2

O)

6

(ZrF

6

) [18] compounds contain

2

6

]

2

8

2

6

2

6

]

2

8

2

6

]

2

8

OH···F and OH···O bonds, the presence of short OH···F bonds (the order of 2.5-2.6 Å) and a

large range of OH···F distances.

The structure of Zn(H

OH···O bonds, but the OH-X length range is small. The Zn(H

The structure of Zn(H O) (ZrF ) is characterized by close OH···F bond lengths and the more

cations.

Frequency-distance correlations of νOH and R(O...F) for stronger H-bonds are evident.

The frequency shift (∆νO-H) was calculated for bands of H O molecules with shorter OH···F

bonds relative to bands for other H O molecules. The ΔνO-H values (240, 167, 46 cm ) for the

Zn(H O) (ZrF ) - Zn(H O) (Zr 10) - Zn(H O) (ZrF ) compounds indicate simplification of

2

O)

6

(Zr

2

F10) with the polymer anion (Zr CN 8) also has OH···F and

O) ²⁺

polyhedron is less distorted.

2

6

2

6

2

+

symmetrical Zn(H

2

O)

6

2

-1

2

[

2

6

]

2

8

2

6

2

F

2

6

the network H -bonds, overall weakening of H-bonds and decrease in the average lengths of Zn-

O bonds.

It is also possible to compare Zn(H

2

O) ²⁺

O)

6

cations and hydrogen bonds in compounds with

MF (M=Zr, Ti, Sn), one can see that the shape

different anions. Analyzing IR spectra Zn(H

2

6

and frequencies of νO-H bands are similar [18, 24] (Table S1). The same way the Zn-O distances

and O-H···F bond lengths are close in these structures.

The significant change in the nature of the anion in Zn(H

manifested by the weakening of O-H···F bonds. Accordingly, in the spectrum of

Zn(H O) 12), a high-frequency shift and better resolution of νO-H bands are observed, in

contrast to Zn(H O) MF

ZnZr O. According to the TG data, heating up of hexahydrate up to 110°C leads to

the formation of ZnZr O tetrahydrate. One can assume that initially water molecules

were removed from the trans-positions of the octahedral Zn(H cation, as was earlier

O) ²⁺

demonstrated for dehydration of ZnZrF ∙6H O→ZnZrF ∙4H O [18]. One can suggest on the

O(1) and H O(2) water molecules bonded to the

2

O)

6

(B12F12) hexahydrate [22] is

2

6

(B12F

2

6

.

2

F10∙4H

2

F10∙4H

2

6

2

6

2

basis of the structure of 1 analysis that H

2

terminal F(3) atoms are detached first.

In the lattice of ZnZr

six due to two terminal F atoms from the neighboring anion layers, thus making them closer and

forming the [Zn(H O) ] polyhedron. In this way, every Zn atom placed directly between the Zr

2

F10∙4H

2

O, Zn(H

2

O) ²⁺

4

cations increase their coordination sphere up to

2

F

4 2

atoms of the upper and lower layers. The formed polymer anion sublattice (ratio Zr/Zn=2) would

be characterized by two types of terminal bonds: Zr-F-Zn and Zr-F∙∙∙H-O. The band with two

-

1

maxima at 3519 and 3430 cm is registered in the range of stretching vibrations of H

molecules (Fig. 4b). The clearly shaped intensive bending δH O band exhibits a single maximum

O molecules in the structure of tetrahydrate

2

O

2

-1

at 1635 cm . This supports that the positions of H

2

are similar.

The described positions of the outer-sphere cations in the crystal lattice and formation of the

2

+

mixed fluoridohydrate shell of Zn was also reflected in the IR spectrum (Fig. 5b). One can see

-1

that the shift (from 540 to 528 cm ) and the decrease intensity of the νasZr-F∙∙∙H-O band occur.

-1

Moreover, a new band at ~450 cm can be assigned to νasZr-F-Zn stretching mode (Table 3).

In the Raman spectrum of ZnZr O, the positions of the main bands for stretching

vibrations of the [ZrF ] group remains the same (Fig. 5b). Thus, the local environment of the Zr

atom in the anionic sublattices of tetra- and hexahydrates are similar. However, some

2

F10∙4H

2

8

-1

redistribution of the bands intensites at 547 and 372 cm is observed, which may be

presumably caused by change in the cations composition. Also, a high-frequency shift of the

-1

bands (252→265 cm and 177→192 cm ) can be explained by the energy increase of the

bending and lattice vibrations in the anion layers due to their approaching to each other and

formation of F-Zn-F bonds.

ZnZr

2

F

10∙2H O. Further dehydration leads to formation of the dihydrate. In the lattice, the

2

+

outer-sphere Zn(H

2

O)

2

cation supplements its coordination already due to four F atoms from

two neighboring anion layers, thus additionally making them closer. In this case, to realize

equivalent interactions of Zn-F in the lattice, each Zn atom must occupy an equally distant

position from two Zr atoms of each layer, thus forming the 2Zr-2F-Zn-2F-2Zr bonds. The

suggested structural rearrangement in the cation sublattice leads to changes in the IR spectrum:

-1

half-width and intensity of the band with the maximum at ~468 cm (νasZr-F-Zn) increase (Fig.

c).

5

According to the changes in the Raman spectrum of ZnZr

2

F

10∙2H O, fundamental changes in

2

the Zr atoms local surrounding occurs. The ν

s

Zr-F band is expanded and shifted towards the

-1

high-frequency range: 547→560 cm . The shift of the band is observed (372→353 cm ) with

predominant contribution of the bridging F-atoms, its half-width increases and the contour

becomes nonsymmetrical. This indicates to formation of weakened bridging Zr-F-Zr bonds of

different types in the fluoridozirconate layer.

At the same time, the Raman spectrum of ZnZr

2

F

10∙2H

2

O demonstrates the intensity

increase for the band at 485 cm , which is characteristic for decrease of the local symmetry of

anion and was earlier demonstrated on the example of the spectra of ZnZrF ∙2H O [18]. The

-1

6

2

indicated band is related to the vibration of the edge Zr-2F-Zr bond, in which the both fluorine

atoms move across the directoion of bridging bonds, remaining their plane. In the same

frequency range there are valence non-totally symmetric stretching vibrations. Also, splitting of

-1

the lattice vibrations band into two components (183 and 170 cm ) is observed, which is

characteristic of the layered structure of the anion and can be related to the presence of two

different interatomic Zr…Zr distances. This is a rather possible option at realization of two types

of the bridging bonds – peak and edge – in the anion layer.

Changes in the dihydrate structure were reflected on the positions of vibration bands of H

molecules. The band of H O stretching vibrations in the IR spectrum demonstrated two well-

expressed maxima at 3504 and ~3564 cm (Fig. 4c). They can be assigned to the symmetric

and asymmetric components (ν , ν ) of streching of the O-H bonds, respectively, since the ν

peak also is intensive in the Raman spectrum. The narrow symmetric bending δH O band

exhibits only one maximum at 1622 cm . As judged from the insignificant position changes of

O molecules vibrational bands, two Zn-O bonds of the Zn(H cation remaining in the

O) ²⁺

dihydrate structure are not directed towards the anion layers and the hydrogen bonds

corresponding to them are weakened. In this case, formation of [Zn(H O) ] polyhedra leads to

their tetragonal deformation due to the decrease of the Zn-H O bond length and the increase of

2

O

2

-1

1

3

1

2

-1

H

2

F

2 4

2

-1

Zn-F bonds length. The low-frequency position of librations of H

confirmes their participation in weak hydrogen bonds.

2

O molecules at 630 cm

ZnZr

2

OF

8

. The IR spectrum of the product with the suggested composition of ZnZr OF

2

8

fabricated by heating up the initial compound 1 at 400ºC, is presented by a broad asymmetrical

-1

band with a maximum at 528 cm , while in the ZnZrF

This shift confirms slight changes of the Zr-F bonds. The appearance of a shoulder at 468 cm is

possibly related to hygroscopicity of ZnZr OF and impurity dihydrate formation. A medium-

intensity band at 872 cm corresponds to the mode νZr-O (Fig. 4d).

To sum up, the structural transformation ZnZr O→ZnZr

decrease of the Zr CN from 8 to 6 and change in the coordination surrounding of Zn cations:

Zn(H O) ] → [Zn(O/F) ] [20]. Similar transformations were observed earlier at the transition

ZnZrF ∙2H O → ZnZrF (cub.) ↔ ZnZrF (hex.) [18] also accompanied by the decrease of the Zr

CN down to 6 and changes in the Zn local surrounding due to composition changes of the

complex cation: [Zn(H O) ]→[ZnF ]. The decrease of F/Zr<5 ratio and simultaneous inclusion

6

(hex.) it is located at 522 cm [18].

-1

2

8

-1

2

F

10·2H

2

OF is related to the

8

[

2

F

4

6

2

6

2

+

2

F

4

6

of O along with F atoms into the complex anion are stabilized the structure of the high-

temperature cubic modification of Zn oxofluoride.

Upon heating of 1 up to 500ºC, the pyrohydrolysis degree is increased and a mixture of

Zr

7

O

9

F

10 and ZnF

2

is formed as the result of partial decomposition of ZnZr

2

OF . Spectroscopic

8

data of Zr

7

O F

9

10 are given in [29].

2

.4. NMR data

The ¹⁹F NMR spectrum of ZnZr

nonsymmetrical broad line with weakly expressed fine structure, which becomes more expressed

2

F

10·6H O at 150 K is represented by a slightly

2

upon the increase of temperature (Fig. 6a). The shape of the ¹⁹F NMR spectrum of

ZnZr O within the temperature range 150-420 K appears to be less symmetrical,

2

F

10·2H

2

signifying the increase of anisotropy of the magnetic shielding tensor of the bridging fluorine

atoms (‘responsible’ for the intensive central part of the hexahydrate spectrum). The latter can be

related to the changes in the terminal fluorine F(3) atoms coordination: transformation of Zr-

1

9

F∙∙∙H-O fragments into Zr-F-Zn ones. According to the F NMR data, no motions of the fluoride

or the fluorine-containing fragments take place in the compounds within the studied temperature

ranges (Fig. 6a, b); the small temperature changes in the spectra are related to the motion of the

water molecules.

1

The low-temperature H NMR spectra of ZnZr

2

F

10·6H O and its partially dehydrated phases

2

are represented by a Pake doublets (Fig. 7). The splitting of the doublet 2α is determined by the

-3

interprotonic distance r according to the formula α = 3/4γℏr , where γ is the gyromagnetic ratio

and ℏ is reduced Planck constant [30]. The splitting value for the hexahydrate is rather high and

equals to ~57-54 kHz at 135-270 K, which must correspond to the considerably shortened

interprotonic distance of 1.49-1.46 Å. It is suggested that the increased splitting of the Pake

doublet is caused by the dipole-dipole interactions of protons with the neighboring fluorine, or

water molecule protons in the Zn(H

2

O) ²⁺

ion.

6

Within the temperature range 270-300 K, a jump-like decrease of the doublet splitting down

to 33 kHz takes place. Changes in the spectrum shape are caused by the initiation of reorientation

2

+

of Zn(H

2

O)

6

cations followed by the transformation of the dipole-dipole interprotonic

interactions tensor [31]. The H-H vectors have virtually two directions in the structure which is

2

+

preserved during the Zn(H

2

O)

6

ion reorientation, therefore the dipole-dipole tensor is not

averaged to zero as it would be in result of H-H vector isotropic reorientation.

1

The splitting of the tetrahydrate H NMR spectrum at 150 K constitutes 59 kHz. The

narrowing of the Pake doublet due to the reorientational water molecule motions starts at

temperatures as low as 170-200 K. Central part of the spectrum contains additional intensity

which can be related to the interaction of the water molecule protons with fluorine in the

coordination sphere of zinc.

1

The H NMR spectra of ZnZr

2

F

10·2H O correspond to the rigid water molecules and are

2

represented by the Pake doublet with “conventional” splitting of 53 – 47 kHz at 220 – 450 K. At

temperatures above 220 K the central part of the spectra of the investigated hydrates contains the

1

small narrow component which corresponds to the sorbed water impurity. The H MAS NMR

spectra of ZnZr

2

F

10·nH O contain single peak at 5.1 ppm for hexa-and dihydrates and at 5.4 ppm

2

for the tetrahydrate. Similar chemical shift (CS) values signify that the water molecules positions

in the dihydrate structure remain in the coordination of zinc ions.

1

9

It is known that the CS of the signals in the F NMR spectra of the fluorozirconates are

dependent on the composition (on the nature of the cation and the cation/Zr ratio) and the local

structural environment (structural role) of a given fluorine [32-34]. The type of linking of the

fluoridozirconate polyhedra realized in ZnZr

2

F

10·6H O is also characteristic for several another

2

1

9

fluoridozirconates. It can be assumed that the relative position of the signals in the F NMR

MAS spectra of these compounds will be similar, and the differences will be determined by a

difference in the interlayer distance and bond lengths, which depend on the cation size and

nature. In simple terms, the layer can be represented consisting of identical fluoridozirconate

bisdisphenoids (dodecahedra). Note that the four vertices of the dodecahedron are located at

short distances from its center, while the other four form longer bonds. In the investigated

structure, one dodecahedron is linked to three others in the layer by the edges: two of them are

located in the layer plane and the third one – perpendicular to it (Fig. 2). Those dodecahedron

edges, which were perpendicular to the layer plane, contain F(1) atoms forming two long bonds

each with zirconium atoms, while the edges parallel to the indicated plane contain F(2) atoms

linking zirconium atoms by a nonsymmetrical bridging bond. The two dodecahedron vertices

F(3) located at short distances do not form bridging bonds. Therefore, there are three types of

fluorine atoms in the structure with different bond lengths to the central atom. The amount of

F(1), F(2), and F(3) atoms accounted for one zirconium atom equals to 1, 2, and 2 respectively. It

is suggested [32] that the terminal atoms could exhibit relatively high shielding anisotropy, while

1

9

the F NMR MAS signals of the atoms located at shorter distances from the central atom, would

be located in the region of weaker magnetic fields.

1

9

The F NMR MAS spectrum of ZnZr

the main phase and having the chemical shifts of 15.1, -11.6, and -32.6 ppm, respectively (Fig.

), the signals of the low intensity and the spinning sidebands. The first of the signals is related

2

F

10·6H

2

O consists of signals a, b, and c belonging to

8

to the atom with relatively high magnetic shielding anisotropy. The spectrum was fitted with

Lorentzian components with an error of 4% and the integrated intensities of the components a, b

and c taking in account their respective spinning sidebands (Table 4, see also Table S2) and

excluding the signals of the impurity were found to be related as 33:41:26. Considering the

above suggestions, the signals can be assigned to the fluorine atoms F(3), F(2), and F(1),

respectively. A number of factors could impair the proper determination of the integrated

intensities: overlapping of the peaks, non-uniform excitation, different T of the fluorine sites

2

due to the difference in disposition relative to the effective relaxation centers such as a mobile

and quadrupole nuclei. Taking it into account, the ratio can be considered satisfactory agreeing

with the one (2:2:1), implied by our assignment of signals. The intensity of the impurities

constitutes 9% and corresponds mainly to the admixture of the tetrahydrate phase formed in the

conditions of MAS experiment (rotational heating up to 60 C under the high pressure).

It can be instructive to compare the CS of signals reported above with the one obtained for

the Zn

isolated ZrF

Zn ZrF ·6H

2

ZrF

8

·12H

polyhedra (n=8 and 6, respectively) and the Zn(H

O contains a single peak with the chemical shift of -42 ppm. The position of this

2

O and ZnZrF

6

·6H

2

O [27]. The structures of both compounds are built from the

n

2

O) units. The spectrum of

6

2

8

2

peak corresponding to the nonbridging fluorines is shifted towards the high magnetic field

further than the signals of the fluorine forming the longest bridging bonds in the spectrum of the

ZnZr

discussed compounds, thus the Zn

NMR shift scale. The single peak in the spectrum of the ZnZrF

corresponding to the decreased Zn to Zr ratio. Additional lowfield shift of the non-bridging

2

F

10·6H

2

O. It can be explained taking into account the “inverse” Zn to Zr ratios in the

1

9

2

ZrF

8

·6H

2

O signal is shifted towards the “ionic” side of the F

·6H O has CS of -13 ppm,

6

2

fluorine signals of ZnZr

2

F

10·6H O can be due to the effect which have the formation of a

2

0

bridging bond by the d metal fluoridocomplexes on the chemical shifts of the neighbouring

fluoride ligands and especially the ligands in the “trans” position relative to the bridging one

[

35].

Dehydration of the initial compound to ZnZr

2

F

10·4H O resulted in shifting of the signals in

2

1

9

the F MAS NMR spectrum (Fig. 8). The signal of the bridging F atoms in the layers plane (b)

also splits into a pair of signals b and b’ near -6.7 and -17.1 ppm. It can be concluded that the

transition from ZnZr

2

F

10·6H

2

O to ZnZr

2

F

10·4H O does not result in significant changes of the

2

fluoridozirconate chain, which is in accordance with the vibrational spectroscopy results. The

changes in the cation sublattice due to transformation of the terminal bonds from Zr-F(3)∙∙∙H-O

to Zr-F-Zn ones lead to the greater length spreading of the bridging Zr-F-Zr bonds in the layer

plane, which is reflected in the splitting of the MAS NMR peaks.

1

9

According to the F MAS NMR spectrum of the ZnZr

2

F

10·2H O (Fig. 8), the variation of

2

the compound structure upon the further dehydration is more substantial. Signals in the spectrum

are shifted towards the gravity center, and the distance between them is decreased. This can be

related to the fact that only the terminal Zr-F-Zn bonds are formed in the structure, while the

length spreading of the bridging bonds decreased. The splitting of signals, which was observed

in the tetrahydrate spectrum, is absent for ZnZr

2

F

10·2H O. The resolution of the dehydrated

2

samples spectra is decreased; an admixture of the Gaussian function to the function of the

component shape was necessary to obtain a good fit. The lowering of the resolution is related to

the formation of the multiple structural defects upon dehydration.

The groups of signals similar to ones discussed above can be also observed in the spectra of

O)ZrF ·H O and (H O)ZrF ·2H O acids (Fig. 8), containing the fluoridozirconate layers of

(H

3

5

2

3

5

2

the same structure. The exact signal positions in the NMR spectra and the shape of the sideband

envelope, despite the isotypism of these compounds, differ substantially. The redistribution of

the intensities between the central signals and the corresponding spinning sidebands indicates the

significant changes in the chemical shielding anisotropy of the fluorine sites. Due to the

overlapping of the ‘a’ and ‘c’ peak sidebands on the spectra of (H

estimate the integrated intensities only for the (H O)ZrF ·H O (Table 4, Table S2). The ratio of

intensities (26:54:20) is similar to the one obtained for ZnZr O (n = 2, 4). The intensity

3

O)ZrF

5

·2H

2

O, we could

3

5

2

F

10·nH

2

of the ‘c’ peak exactly corresponds to the population of the perpendicular to the layer plane

edge-bonding fluorine sites, but the error due to the intensity redistribution between ‘a’ and ‘c’

peaks is rather large. It can be noted that both for the salts and the acids the more molecules of

the structural water it contains, the more isotropic the average chemical shift of the fluorine sites

and the more symmetric the NMR spectrum become (Figs 6 and 8).

3

. Conclusions

The crystal structure of the first time synthesized high-aqueous crystal hydrates of the

composition ZnZr

2

F

10∙6H

2

O has been investigated. The crystal structure of 1 is built of flat

O)

]²⁺cations. The complex cations

2

2

networked _



Zr F



anion layers and octahedral [Zn(H

2

6

2

10

and anions are linked in the structure into a three-dimensional framework by the O–H···F and

O–H···O hydrogen bonds.

Thermal decomposition of ZnZr

TGA and DTA. Decomposition in the temperature range 50-850°C is proceeded through the

following stages: ZnZr O → ZnZr O → ZnZr O → ZnZr OF with

formation of the mixture of the final products ZnO and ZrO

2

F10∙6H

2

O in air has been investigated via the methods of

2

F10∙6H

2

F10∙4H

2

F10∙2H

2

8

2

.

1

9

1

19

The F, H NMR and F MAS NMR spectroscopy data on the initial compound and the

intermediate products of its decomposition have been obtained, systematized, and summarized. It

has been established that the compounds containing the investigated type of fluoridozirconate

layers, in which each Zr-polyhedron has three edge-sharing bonds with three neighboring

polyhedra, have characteristic ¹⁹F MAS NMR spectra containing the signals from three

magnetically inequivalent fluorine atoms.

4

. Experimental

4

.1. Synthesis

Materials: ZrO(NO

40%, Reachem (Russia), 99.99% purity), Zn(NO

.34 g (0.02 mol) of zirconyl nitrate dihydrate (analytical pure grade) was dissolved in 10 ml

O and 4 ml 40% HF (special pure grade) at room temperature. Then 2.97 g (0.01 mol) of

crystalline Zn(NO ∙6H O (chemical pure grade) was added to the solution. During natural

3

)

2

-2H

2

O (Reachem (Russia), >99% purity), solution of hydrofluoric acid

(

3

)

2

∙6H O (Reachem (Russia), >98.5% purity).

2

5

of H

2

3

)

2

evaporation and at room temperature, a crystalline precipitate was formed from the reaction

mixture in the form of thin transparent hexagonal plates.

The results of the elemental analysis of the obtained precipitate (found, %): Zn 12.0; Zr

3

3.3; F 34.7; for ZnZr

2

F

10∙6H O (calculated, %): Zn 11.93; Zr 33.40; F 34.86.

2

4

.2. Crystal structure determination

Further details on the crystal structure investigation can be obtained from the

Fachinformationszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen, Germany, on request

of the depository number CSD – 1934690.

The X-ray experiment was performed using a BRUKER Kappa Apex2 diffractometer

(

MoK - radiation, graphite monochromator). The data reduction and multi-scan absorption

α

correction were performed using the Bruker Apex2 program [36]. The structure was solved

using direct methods and refined by least-squares calculation in anisotropic approximation for

non-hydrogen atoms [37, 38]. Hydrogen atoms of H O molecules (except for one H atom

2

bonded with O(3)) were located in difference Fourier maps and included into the final structure

refinement with fixed positional parameters and Uiso(H)=1.5Ueq(O). Main crystallographic

data, experimental parameters, and the structural refinements were provided in Table 5.

4

.3. TG-DTA

Thermal investigation of ZnZr

using a Q-1000 MOM derivatograph at a heating rate of 5 deg/min up to 820°C. The sample

weight equals to 120 mg. The ZnZr O (n=4, 2) crystal hydrates were prepared through

thermal dehydration of hexahydrate by heating it at the rate of 2.5 deg/min up to 110 and 200°C,

respectively: here, the weight loss equals to 6.7 and 13.3 %. Calcined Al was used as a

standard. Identity of the decomposition products was confirmed via the X-ray diffraction patterns

Fig. S3).

2

F10∙6H

2

O was conducted in air (relative humidity of ~20 %)

2

F10∙nH

2

O

3

(

4

.4. Vibrational spectroscopy

The Raman spectra of the investigated compounds were recorded using an RFS100/S

-1

spectrometer (laser Nd:YAG, λ=1064 nm) with the resolution of 4 cm . The IR spectra were

-1

obtained at room temperature using an IR-Affinity device in the range 4000-400 cm from the

samples prepared as suspension in paraffinic oil on the KRS-5 frame.

4

.5. NMR spectroscopy

1

19

NMR H, F spectra were recorded on Bruker Avance AV-300 spectrometer with one-pulse

static) and Hahn-echo (MAS) sequences. Sample rotational frequencies in ¹⁹F MAS NMR

(

experiments were varied from 10 to 18 kHz to detect the isotropic peak positions. Chemical

1

9

1

shifts of signals in F and H NMR spectra were measured relative to CFCl

3

and Si(CH ) ,

3

4

1

19

respectively. Static H and MAS F NMR spectra were fitted with Gaussian-broadened Pake

and Gaussian/Lorentzian sum functions, respectively, by the minimal sum of squared deviation

criteria in a home-made program.

Declaration of interests

The authors declare that they have no known competing financial interests or personal

relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The work was supported within the frames of the State Order of the Institute of Chemistry

FEBRAS, project No. 265-2019-0001.

References

V.Ya. Kavun and V.I. Sergienko, Diffusion Mobility and Ion Transport in Crystalline and

[

1].

Amorphous Fluorides of Elements of Group IV and Antimony (III), Dal’nauka,

Vladivostok, 2004. (Russ.)

[

2].

3].

R.L. Davidovich., V. I. Sergienko, Structural chemistry of complex fluorides of titanium

(

IV), zirconium (IV) and hafnium (IV), Dal’nauka, Vladivostok, 2016. (Russ.)

P. Charpin, M. Lance, M. Nierlich, J. Vigner, J. Lambard, Structures of oxonium

pentafluorozirconate mono- and dihydrates, Acta Crystallogr. Sect. C 44 (1988) 1698-

1

701. doi.org/10.1107/S0108270188005797.

[

4].

R.E. Sykora, M. Ruf, M. Albrecht-Schmitt, Organically Templated Zirconium Fluorides:

Hydrothermal Syntheses, Structural Relationships, and Thermal Behavior of

·H O, J. Solid State Chem. 159 (2001) 198-203.

2

doi: 10.1006/jssc.2001.915.

[

5].

6].

7].

A.V. Gerasimenko, R.L. Davidovich, V.B. Logvinova, Crystal structures of layered

zirconium pentafluorides of methylammonium, glycinium, and β -alanine, Russ. J. Struct.

Chem. 52 (2011) 524-530. doi.org/10.1134/S0022476611030115.

A. Ben Ali, M. Body, M. Leblanc, V. Maisonneuve, 2D Zirconium Fluorides: Synthesis,

Structure and NMR Spectroscopy, Solid State Sci. 13 (2011) 394-398.

0.1016/j.solidstatesciences.2010.11.044.

D. Avignant, I. Mansouri, R. Chevalier, J.C. Cousseins, Crystal structure and fast ionic

conduction of TlZrF , J. Solid State Chem. 38 (1981) 121-127. doi: 10.1016/0022-

596(81)90481-3.

doi:

1

5

4

[

8].

9].

V.V. Tkachev, R.L. Davidovich, L.O. Atovmyan, Crystal structure of anhydrous

ammonium pentafluorozirconate, Russ. J. Coord. Chem. 17 (1991) 1483-1484.

Y.Gao, J. Guery, A. Le Bail, C. Jacoboni Synthesis, X-ray single crystal structure

determination, and dehydration study of BaZr

thermodiffractometry, J. Solid State Chem. 98 (1992) 11-24. doi.org/10.1016/0022-

596(92)90065-4.

2

F

10·2H

2

O by X-ray powder

4

[

10]. V. Gaumet, M. El-Ghozzi, D. Avignant, Crystal Structure of KZrF

Inorg. Chem. 34 (1997) 283-293.

5

, Eur. J. Solid State

11]. M.M. Godneva, D.L. Motov, Chemistry of fluorides of zirconium and hafnium, Nauka,

Leningrad, 1971. (Russ.)

12]. B.V. Bukvetskii, A.V. Gerasimenko, R.L. Davidovich, Crystal structures of ammonium

3.

ZrF , Russ. J. Coord. Chem. 17 (1991) 35-

6

4

[

13]. E.I. Voit, A.B. Slobodyuk, N.A. Didenko, A Study of the Composition, Ionic and

Molecular Mobility, and Thermal Properties of Ammonium Pentafluoridozirconate

Hydrates, Opt. Spectrosc. 125 (2018) 888–897. doi:10.1134/S0030400X19020243. Russ.

Optics and Spectroscopy 126 (2019) 147-155.

[

14]. J.P. Laval, B. Frit, Crystal structure of the β-BaZr

ReO -type and the fluorozirconate glasses, J. Solid State Chem. 72 (1988) 181-192.

doi:10.1016/0022-4596(88)90021-7.

2

F10 compound. Relations with the

3

[

15]. M.C. Marignac, Recherches chimiques et cristallographiques sur les fluozirconates.

Formule de la zircone. Ann. chim. phys. 60 (1860) 257-307.

16]. M.M. Godneva, D. L. Motov, V. Ya. Kuznetsov, M.P. Riskina, Phasetransformation in

systems ZrO

2

-H

2

SO

4

-HF-Zn(NO

3

)

2

-H O, Russ. J. Inorg. Chem. 49 (2004) 1198-1204.

2

17]. M.M. Godneva, V. Ya. Kuznetsov, D. L. Motov, Characteristics of nickel fluoro- and

oxofluorozirconates, Russ. J. Inorg. Chem. 50 (2005) 1263-1268.

18]. E.I. Voit, N.A. Didenko, K.A. Gayvoronskaya, A.V. Gerasimenko, Structure of

ZnZrF

6

·nH

2

O (n = 6–2) and ZnZrF

6

crystallohydrates according to vibrational

121 (2016) 229-240.

spectroscopy

data, Opt. Spectrosc.

doi:10.1134/S0030400X16080233. Russ. Optics and Spectroscopy 121 (2016) 248–259.

19]. R.E. Marsh, Structure of oxonium pentaltuorozirconate dihydrate, Acta Crystallogr., Sect.

C 45 (1989) 980. doi.org/10.1107/S0108270188014672.

[

20]. S. Nakhal, T. Bredow, M. Lerch, Syntheses and crystal structures of new ReO type

3

derived transition metal oxide fluorides, Z. Anorg. Allg. Chem. 641 (2015) 1036-1042.

doi: 10.1002/zaac.201500089.

[

21]. G. Teufer, Acta Crystallogr. Die K ristallstruktur des Natriumhexafluoroantimonats(V),

Acta Crystallogr. 9 (1956) 539-540. doi.org/10.1107/S0365110X56001509.

22]. M.R. Lacroix, Bukovsky EV, M. Lozinšek, T.C. Folsom, B.S. Newell, Y. Liu, D.V.

Peryshkov, S.H. Strauss, Manifestations of Weak O−H···F Hydrogen Bonding in

M(H

Bands and Latent Porosity (M = Mg − Ba, Co, Ni, Zn), Inorg. Chem. 57 (2018) 14983-

5000. doi: 10.1021/acs.inorgchem.8b02786.

2

O)

n

(B12F12) Salt Hydrates: Unusually Sharp Fourier Transform Infrared ν(OH)

1

[

23]. Herzberg, G. Molecular Spectra and Molecular Structure. II. Infrared and Raman Spectra

of Polyatomic Molecules, Van Nostrand Reinhold: New York, NY, 1945.

24]. R.L. Davidovich, T.A. Kaidalova, T.F. Levchishina, V.I. Sergienko, Atlas of Infrared

Absorption Spectra and X-ray Powder Diffraction Data of Group IV–V Metal Fluoride

Complexes, Nauka, Moscow, 1972. (Russ.)

[

25]. G.E. Walraffen, M.S. Hokmabady, S. Guha, P.N. Krishnan, Low-frequency Raman

investigation of lead-cjntaining fluorozirconate glasses and melt, J. Chem. Phys. 83

(1985) 4427-4443. doi.org/10.1063/1.449061.

26]. E.I. Voit, N.A. Didenko, K.N. Galkin, Vibrational spectra of zirconium fluoride

complexes with different structures of anionic sublattice, Opt. Spectrosc. 118 (2015) 114-

1

24. doi.org/10.1134/S0030400X15010257. Russ. Optics and Spectroscopy 118 (2015)

18 128.

[

27]. E. Voit, N. Didenko, K. Gayvoronskaya, A. Slobodyuk, A. Gerasimenko, Synthesis and

Complex Study of the Crystal Hydrate Zn ZrF ·12H O, Z. Anorg. Allg. Chem. 642

2016) 643–651. doi:10.1002/zaac.201600123.

2

8

2

(

[

28]. T.K. Chattopadhyay, F. Devreux, K. Peters, B. Ghosh, E. Gmelin, E.M. Peters,

Crystal structure and phase transitions in MnTiF ·6(H O) and ZnTiF ·6(H O), J. Phys. C:

Solid State Phys. 21 (1988)1321-1334 . doi.org/10.1088/0022-3719/21/8/009

29]. E.I. Voit , N.A. Didenko, K.A. Gaivoronskaya, The Composition of Intermediate

Products of the Thermal Decomposition of (NH

Spectroscopy Data, Opt. Spectrosc.

4

)

2

ZrF

6

to ZrO

2

from Vibrational-

328-336.

124

(2018)

doi:10.1134/S0030400X18030207. Russ. Optics and Spectroscopy 124 (2018) 333–340.

[

30]. A. Abragam, Nuclear Magnetism, Clarendon Press, Oxford, 1961.

31]. N.A. Sergeev, O.V. Falaleev, S.P. Gabuda, NMR spectra of diffusing water molecules in

crystals, Sov. Phys. Solid State. 11 (1970) 1815-1818.

[

32]. R.E. Youngman, S. Sen, A high-resolution ¹⁹F NMR spectroscopic study of barium

fluorozirconate glasses and related crystals, Solid State Nucl. Magn. Reson. 27 (2005)

7

7-89. https://doi.org/10.1016/j.ssnmr.2004.06.008.

33]. A. Rakhmatullin, M. Boča, J. Mlynáriková, E. Hadzimová, Z. Vasková, I.B. Polovov, M.

Mičušík, Solid state NMR and XPS of ternary fluorido-zirconates of various coordination

modes,

https://doi.org/10.1016/j.jfluchem.2018.01.010.

34]. A.V. Gerasimenko, K.A. Gaivoronskaya, A.B. Slobodyuk, N.A. Didenko, Magnesium

Hexafluoridozirconates MgZrF ·5H O, MgZrF ·2H O, and MgZrF : structures, phase

transitions, and internal mobility of water molecules, Z. Anorg. Allg. Chem. 643 (2017)

785–1792. https://10.1002/zaac.201700166.

J.

Fluorine

Chem.

208

(2018)

24-35.

[

6

2

6

2

6

1

9

[

35]. Y.A. Buslaev, E.G. Ilyin, F chemical shifts and mutual influence of ligands, J. Fluorine

Chem. 25 (1984) 57-67. https://doi.org/10.1016/S0022-1139(00)81195-1.

[

36]. Bruker. APEX 2 V.7, Bruker AXS Inc., Madison, Wisconsin, U.S.A. (2010).

37]. G.M. Sheldrick, Acta Crystallogr. SHELXT – Integrated space-group and crystal-

structure determination, A71 (2015) 3 –8. doi: 10.1107/S2053273314026370.

[

38]. G.M. Sheldric k, Crystal structure refinement with SHELXL, Acta Crystallogr. Sect. C 71

(2015) 3–8. doi:10.1107/S2053229614024218.

Fig. 1. Packing of structural units in ZnZr

2

F

10·6H O (hydrogen atoms removed for clear

2

representation).

Fig. 2. Fragment of the fluoridozirconate layer in the structure of ZnZr

2

F

10·6H

2

O.

Symmetry code: (i) –x,y,–z; (ii) –x,–y+1,–z; (iii) x–1/2,–y+1/2,z; (iv) –x+1/2,–y+1/2,–z; (v) –x–

/2,–y+1/2,–z; (vi) –x+2,–y,–z+1].

[

1

Fig. 3. Zn octahedron and fragment of H-bonds system (dote lines) (a) and fragment of the aqua-

cation layer in the structure of ZnZr2F10·6H2O (b).

[

Symmetry code: (vii) x+1,y,z; (viii) –x+1,y,–z+1; (ix) x+1/2,y–1/2,z; (x) –x+1,–y,–z+1 (xi) x,–

y,z; (xii) 2–x,y,1–z; (xiii) 1+x,–y,z, (xiv) 1–x,–y, 1–z; (xv) 3/2–x,–1/2+y1,–z; (xvi) 1+x,y,z].

Fig. 4. IR-spectra of the compounds ZnZr

2

F10∙6H

2

O (a), ZnZr

2

F10∙4H

2

O (b), ZnZr

2

F

10∙2H O (c),

2

ZnZr OF (d). *- the bands of paraffin oil.

2

8

Fig. 5. IR(1) and Raman(2) spectra of the compounds ZnZr

2

F10∙6H

2

O (a), H

3

OZrF

5

∙2H O

2

(

a, dotted line), ZnZr O (b), and ZnZr O (c) in the range of anion vibrations.

2

F

10∙4H

2

F

10∙2H

2

1

9

Fig. 6. F NMR spectra of the compounds ZnZr

different temperatures.

2

F

10·6H

2

O (a) and ZnZr

2

F

10·2H O (b) at

2

Fig. 7. 1H NMR spectra of ZnZr2F10∙nH2O at different temperatures. n = 6 (a), 4 (b), 2 (c).

Fig. 8. 19F MAS NMR spectra of the investigated compounds. Spinning sidebands are

marked with asterisks or left unmarked. The MAS rotational frequencies were 18 kHz for

ZnZr2F10·nH2O and 16 kHz for (H3O)ZrF5·nH2O.

Table 1

Selected geometric parameters (Å) for ZnZr

2

F

10·6H O.

2

Zr(1)…Zr(1)^v

Zr(1)…Zr(1)ⁱ^v

3.5694(3)

Zr(1)–F(2)ⁱⁱⁱ

Zr(1)–F(2)ⁱ^v

2.2202(19)

Zr(1)…Zr(1)ⁱⁱ

Zr(1)–F(3)ⁱ

Zr(1)–F(3)

Zr(1)–F(2)

Zr(1)–F(2)ⁱ

Zr(1)–F(1)

Zr(1)–F(1)ⁱⁱ

3.6970(8)

2.000(2)

Zn(1)–O(1)^vⁱ

Zn(1)–O(1)

Zn(1)–O(2)^vⁱ

Zn(1)–O(2)

Zn(1)–O(3)

Zn(1)–O(3)^vⁱ

2.045(4)

2.085(5)

2.130(6)

2.000(2)

2.0610(17)

2.1780(14)

Symmetry codes: (i) –x,y,–z; (ii) –x,–y+1,–z; (iii) x–1/2,–y+1/2,z; (iv) –x+1/2,–y+1/2,–z; (v)

x–1/2,–y+1/2,–z; (vi) –x+2,–y,–z+1.

–

Table 2

Hydrogen-bond geometry (Å, °) for ZnZr

2

F

10·6H O.

2

O–H···A

O–H

0.86

0.98

0.99

H···A

1.93

1.83

1.69

O···A

 OHA

166

O(1)–H(1)...F(3)^vⁱⁱ

O(2)–H(2)...F(3)^vⁱⁱⁱ

O(3)–H(3)...F(1)ⁱ^x

O(3)...O(3)^x

2.773(2)

2.760(2)

2.669(6)

2.883(12)

156

169

Symmetry codes:(vii)x+1,y,z; (viii) –x+1,y,–z+1; (ix) x+1/2,y–1/2,z; (x) –x+1,–y,–z+1

Table 3

Positions (cm ) and assignments of the characteristic bands in the IR and Raman spectra of

the ZnZr O (n=6, 4, 2) compounds.

-1

2

F10∙nH

2

ZnZr

2

F10∙6H

2

O

ZnZr

2

F10∙4H

2

O

ZnZr

2

F

10∙2H O

2

Assignments^*

IR

R

IR

R

IR

R

5

46

547

560

s

ν Zr-F

5

3

40

98

528

ν

asZr-F∙∙∙HO

5

02

502

s

ν Zr-F ()

br

4

85

474

ν

s

Zr-F

4

50

68

asZr-F-Zn

asZr-Fbr

390

3

2

1

70

52

11

77

35

372

265

353

253

s

Zr-Fbr (═)



ZrF

n

192

147

183, 170

138

ν

s

ZrF

n

-ZrF

n

 ZrF -ZrF

s

n

*

- Assignment of bands: ν – stretching, δ –deformation. Vibrations across () and along (═)

the direction of bridging Zr-F-Zr bonds.

Table 4

¹⁹F MAS NMR data.

Compound

Peak

CS

I

ZnZr

2

F

10·6H

2

O

a

15.1

-11.6

-32.6

30

38

24

8

b

c

*

a

ZnZr

2

F10·4H

2

O

25

23

31

21

22

3

b

b’

c

-6.7

-17.1

-30

*

a

ZnZr

2

F10·2H

2

O

4.8

18

48

24

10

26

53

19

2

b

c

-14.5

-24

*

a

(H

3

O)ZrF

5

·H

2

O

34.5

-9.6

b

c

-21.8

*

marks the total intensity of the admixture peaks

Article Doi

Synthesis and complex study of the crystal hydrate ZnZr2F10?6H2O

DOI: 10.1016/j.jfluchem.2020.109475

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Article abstract of DOI:10.1016/j.jfluchem.2020.109475

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