The influence of organic agents on the resultant crystal structure in the reactions of the [Re 4Te...

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The influence of organic agents on the resultant crystal structure in the reactionsof the [Re4Te4(CN)12]4� tetrahedral cluster anion with Nd3+ cations

Olga A. Efremova, Yakov M. Gayfulin, Yuri V. Mironov ⇑, Natalia V. Kuratieva, Anton I. Smolentsev,Vladimir E. FedorovNikolaev Institute of Inorganic Chemistry, Siberian Branch of Russian Academy of Sciences, 3, Acad. Lavrentiev prospekt, Novosibirsk 630090, Russia

a r t i c l e i n f o

Article history:Received 18 July 2011Accepted 5 October 2011Available online 21 October 2011

Keywords:Rhenium tetrahedral cluster complexesNeodymiumSynthesisCrystal structureOrganic ligands

a b s t r a c t

The reaction of the cluster salt K4[Re4Te4(CN)12]�5H2O with NdCl3�6H2O was studied in either an acidicmedium (HCl) or in a water solution in the presence of the following organic agents: hexafluoroacetyl-acetonate, 2,20-bipyridine or 1,10-phenanthroline (phen). The crystal structures of four new compoundshave been solved by single crystal X-ray diffraction analysis: (H)[{Nd(H2O)5}{Re4Te4(CN)12}]�5.5H2O (1)(space group P21/c, framework structure), K2[{Nd(H2O)7}2{Re4Te4(CN)12}2]�8H2O (2) (space group C2/c,isolated structure), K0.5H0.5[{Nd(H2O)5}{Re4Te4(CN)12}]�3H2O (3) (space group Cmcm, layered structure)and (phenH)[{Nd(H2O)2(phen)2}{Re4Te4(CN)12}]�11H2O (4) (space group C2/c, chain structure). 1,10-Phe-nanthroline was found to have been incorporated into the structure of compound 4, whilst hexafluoro-acetylacetonate and 2,20-bipyridine did not enter the structures of 2 and 3. It was shown that thestructures of compounds 2–4 differ dramatically from that found for compound 1, which was obtainedin the absence of the organic agents.

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1. Introduction

The design of self-assembling systems from pre-made buildingblocks is an area of intense interest as a route to the rational gen-eration of functional materials [1–4]. Mononuclear metallocyanideanion complexes [M(CN)x]m� have been widely explored as thebuilding blocks in the design of coordination polymers withn-dimensional (n = 1, 2, 3) structures due to the ability of the CNligand to be ambidentate and to create the bridges between twometal cations [5–7]. A variety of cationic complexes with 3d and4f metals are used to connect the metallocyanide anions in thesolid state. Such high dimensional systems often show useful mag-netic [8–10], non-linear optical [11,12] or zeolitic [13–15]properties.

The latest progress in cluster chemistry has shown that rheniumchalcocyanide clusters [Re4Q4(CN)12]4� [16] and [Re6Q8(CN)6]4�/3�

(Q = S, Se, Te) [17–26] can also be effectively used in reactions withtransition metal cations for the design of n-dimensional structures.It was shown that the utilisation of 3d metal cations coordinated byN-donor chelating ligands is the most efficient way to control thedimensionality of the resulting structures. The chemistry of chalco-cyanide rhenium clusters are abound with examples where thecoordination sites of the 3d metals are blocked by en [17,23,24],

dien [26–28], trien [25,29], 1,2S,3S,4-butantetraamine [30,31] andothers [16,32,33].

In comparison to the chemistry of rhenium complexes with 3dmetals, the complexes of rhenium clusters with lanthanide cationshave not been thoroughly studied. Up until now a number of pa-pers have described the reactions of Ln3+ cationic complexes(where Ln is a lanthanide cation) with [Re6Q8(CN)6]4�/3� [34–40]and only two with [Re4Q4(CN)12]4� [41,42]. Amongst these papers,there are only three papers, which show the reaction product of[Re6Q8(CN)6]4� with Ln3+ cations coordinated by chelating ligands,namely, 2,20-bipyridine [38], glycerol [39] and meso-erythritol [40].The articles show that these ligands effectively coordinate with therare earth cations resulting in the formation of mono-, bi- or poly-nuclear cationic complexes. The bonding of the cationic complexesby the [Re6Q8(CN)6]4� cluster anion resulted in the formation ofn-dimensional grids.

Two recent articles [41,42] show that the reactions of [Re4Q4-(CN)12]4� with Ln3+ aqua complexes gave compounds possessing3D, 2D and 1D structures. The tetranuclear rhenium cluster anionsare rather different from the hexanuclear type, which predomi-nantly formed 3D structures in similar reactions. It was shown thatboth the coordination number (CN) of the rare earth metal cationand the Q atom in the cluster core {Re4Q4} have a crucial influenceon the dimensionality of the resultant polymer.

In the current work, we made the first attempt to ascertain theinfluence of the presence of organic reactants in the systemLn3+/[Re4Q4(CN)12]4� on the structure and dimensionality of the

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⇑ Corresponding author. Tel.: +7 383 3309253; fax: +7 383 3309489.E-mail address: [email protected] (Y.V. Mironov).

Polyhedron 31 (2012) 515–523

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resultant coordination polymer. We used the appropriate O- or N-donor organic compounds that can block the coordination sitesaround the Ln cation by using a bidentate chelating mode. To meetthe research objective, the crystallisation product from a watersolution containing NdCl3 and the cluster salt K4[Re4Te4(CN)12]�5H2O was compared with products obtained from solutionsadditionally containing organic compounds (potassium hexafluo-roacetylacetonate, 2,20-bipyridine or 1,10-phenanthroline (phen))in the mother liquor. Here we describe the crystal structures offour new compounds (H)[{Nd(H2O)5}{Re4Te4(CN)12}]�5.5H2O (1),K2[{Nd(H2O)7}2{Re4Te4(CN)12}2]�8H2O (2), K0.5H0.5[{Nd(H2O)5}-{Re4Te4(CN)12}]�3H2O (3), and (phenH)[{Nd(H2O)2(phen)2}{Re4Te4-(CN)12}]�11H2O (4).

2. Experimental

2.1. Materials and syntheses

All reagents were used as purchased. K4[Re4Te4(CN)12]�5H2Owas synthesized by the reaction of [Re4Te4(TeCl2)4Cl8] with anaqueous solution of KCN according to the techniques described in[43]. [Re4Te4(TeCl2)4Cl8] was obtained as described in [44]. The FT-IR spectra were recorded on a Scimitar FTS 2000. Semi-quantitativeelemental analysis was made with an energy-dispersive spectrom-eter ETEC AutoProbeTracor-Northern TN-5400 energy-dispersiveX-spectrometer (EDX). The phase individuality of 1–4 was con-firmed with XPD on a Philips PW1700 diffractometer, where thefresh dry crystalline powder samples used had been ground by apestle and mortar. The thermal stability was determined by a Nitz-sch TG 209 F1 Iris instrument.

2.2. (H)[{Nd(H2O)5}{Re4Te4(CN)12}]�5.5H2O (1)

About 0.050 g (0.028 mmol) K4[Re4Te4(CN)12]�5H2O and 0.070 g(0.20 mmol) NdCl3�6H2O were dissolved in 10 mL H2O. HCl (conc.)was added dropwise (3–5 drops) to prevent the possible hydrolysisof the NdCl3 salts. The solutions were heated until their volumeswere reduced to about 2 mL. The dark-coloured crystals that ap-peared after 3 days were filtered and dried. Yield: 0.039 g (74%).EDX: K:Nd:Re:Te = 0.0:1.0:4.0:3.8. FT-IR (cm�1) mCN: 2160m,

2138s. Anal. Calc. for C12H22N12NdO10,5Re4Te4: N, 8.8; C, 7.5; H,1.2. Found: N, 8.7; C, 7.4; H, 1.4%.

2.3. Synthesis of K2[{Nd(H2O)7}2{Re4Te4(CN)12}2]�8H2O (2)

Compound 2 was prepared analogously from 10 mL of an aque-ous solution of K4[Re4Te4(CN)12]�5H2O (0.050 g, 0.028 mmol),NdCl3�6H2O (0.070 g, 0.20 mmol) and sodium hexafluoroacetylace-tonate (0.045 g, 0.20 mmol). Yield: 0.037 g (69%). EDX:K:N-d:Re:Te = 0.9:1.0:4.0:3.8. FT-IR (cm�1) mCN: 2162m, 2135s. Anal.Calc. for C24H44K2N24Nd2O22Re8Te8: N, 8.6; C, 7.4; H, 1.1. Found:N, 8.5; C, 7.2; H, 1.3%.

2.4. Synthesis of K0.5H0.5[{Nd(H2O)5}{Re4Te4(CN)12}]�3H2O (3)

Compound 3 was prepared analogously from 10 mL of an aque-ous solution of K4[Re4Te4(CN)12]�5H2O (0.050 g, 0.028 mmol),NdCl3�6H2O (0.070 g, 0.20 mmol) and 2,20-bipyridine (0.031 g,0.20 mmol). Yield: 0.042 g (81%). EDX:K:Nd:Re:Te = 0.5:1.0:4.0:3.8. FT-IR (cm�1) mCN: 2160m, 2141s. Anal. Calc. for C12H16.5K0.5-N12NdO8Re4Te4: N, 9.0; C, 7.7; H, 0.9. Found: N, 9.0; C, 7.8; H, 1.1%.

2.5. Synthesis of (phenH)[{Nd(H2O)2(phen)2}{Re4Te4(CN)12}]�11H2O(4)

Compound 4 was synthesised in a thin glass tube constricted inthe middle. NdCl3�6H2O (40 mg, 0.112 mmol) and 1,10-phenan-throline (20 mg, 0.111 mmol) were dissolved in 4 mL of water. Thissolution was then layered under 4 mL of an aqueous solution con-taining 20 mg (0.011 mmol) of K4[Re4Te4(CN)12]�5H2O. Four dayslater, red-brown needle-shaped crystals suitable for X-ray investi-gation were formed in the middle of the tube. The crystals wereseparated manually, washed with a small amount of distilled waterand dried on filter paper. The crystals undergo slow decompositionin air, therefore they were analysed by XRDA and TGA shortly afterbeing removed from the mother liquor and dried. Yield: 8 mg(40%). EDX:Nd:Re:Te = 1.0:4.6:4.1. FT-IR (cm�1) mCN: 2137s. Allbands related to the organic ligand are observed. Anal. Calc. forC48H47N18NdO13Re4Te4: N, 9.6; C, 23.6; H, 2.1. Found: N, 10.1; C,23.2; H, 2.1%.

Table 1Crystal data and structure refinement parameters for compounds 1–4.

1 2 3 4

Empirical formula C12H22N12NdO10.5Re4Te4 C12H22KN12NdO11Re4Te4 C12H16.5K0.5N12NdO8Re4Te4 C48H25N18NdO2Re4Te4

Formula weight 1901.86 1948.96 1875.86 2285.30Space group P21/c C2/c Cmcm C2/ca (Å) 12.8171(3) 21.9014(8) 15.6175(11) 18.3661(11)b (Å) 17.2131(5) 13.7576(5) 21.6311(11) 30.2555(17)c (Å) 16.9466(5) 25.2973(10) 20.7773(12) 13.4135(6)a (�) 90 90 90 90b (�) 108.736(1) 106.599(1) 90 99.817(2)c (�) 90 90 90 90V (Å3) 3540.67(17) 7304.7(5) 7019.1(7) 7344.4(7)Z 4 8 8 4qcalc (g/cm3) 3.568 3.544 3.550 2.067Crystal size (mm) 0.21 � 0.05 � 0.05 0.22 � 0.03 � 0.02 0.16 � 0.08 � 0.02 0.25 � 0.06 � 0.04F(000) 3320 6824 6512 4092l (mm�1) 18.355 17.910 18.568 8.863Tmax/Tmin 0.4605/0.1134 0.7159/0.1104 0.7077/0.1551 0.7182/0.5310h Range (�) 2.37–26.37 1.77–27.48 2.54–27.48 1.35–30.14Reflections collected 22208 25404 24392 16634Unique reflections 7122 8318 4271 10656Rint 0.0401 0.0184 0.0281 0.0362Parameters refined 388 409 215 375R1/wR2 (I > 2r(I)) 0.0311/0.0685 0.0178/0.0421 0.0192/0.0490 0.0664/0.1677R1/wR2 (all data) 0.0617/0.0755 0.0214/0.0430 0.0214/0.0497 0.1185/0.1901Goodness-of-fit (GOF) on F2 0.972 1.047 1.068 0.96

516 O.A. Efremova et al. / Polyhedron 31 (2012) 515–523


2.6. X-ray crystallographic data collection and refinement of thestructures

The structures of all the compounds were solved by single crys-tal X-ray diffraction analysis. Suitable single crystals of 1–4 wereseparated manually from the mother liquors and mounted onto aBruker Nonius X8 Apex 4 K CCD diffractometer fitted with graphitemonochromatized MoKa radiation (k = 0.71073 Å). The data werecollected at 293 K for compounds 1–3 and at 150 K for compound4 by a standard technique [45]. Absorption corrections were madeempirically using the SADABS program [45]. The structures weresolved by the direct methods of difference Fourier synthesis andfurther refined by the full-matrix least-squares method using theSHELXTL program package [46]. All non-hydrogen atoms were refinedanisotropically. The positions of the hydrogen atoms of 1,10-phe-nanthroline were calculated corresponding to their geometricalconditions and refined using the riding model. Hydrogen atomsof the water molecules and in the cationic unit phenH (compound4) were not located. Crystal data and details of the final refinementare given in Table 1.

In order to assess any remaining voids, the SQUEEZE and VOIDoptions of the PLATON software package [47,48] were used for themodels of the structures of 1–4, where all solvating water mole-cules were removed. Though the total potential solvent space per-centage in relation to the unit cell volumes were estimated as 25%,17%, and 22% for compounds 1, 2, and 3, respectively, no reallyremarkably large voids were found in their structures. The total po-tential solvent volume corresponds to 5.5, 7.5, and 4.5 H2O, respec-tively for compounds 1, 2, and 3, where 40 Å3 was accepted as thevolume essential for one solvating water molecule. The obtainednumbers are thus in good correlation with the compositions ob-tained from the SHELXL refinement.

The structure of compound 4 presented special problems, as itcontains large channels. The refinement proceeded to defineclearly the positions of all atoms in the cluster anion and in the cat-ionic unit {Nb(H2O)2(phen)2}3+, as well as in one uncoordinateddisordered 1,10-phenanthroline molecule. SQUEEZE found two1168 Å3 voids at (1/2, 0, 0.031) and (1, 1/2, 0.019), each corre-sponding to 16% of the cell volume. SQUEEZE removed 353e� fromeach void. According to EDX analysis and elemental analysis nopotassium cations or extra molecules of 1,10-phenanthroline arepossible in compound 4. Thus, we propose that the only possible‘‘guest’’ molecules in voids can be water molecules. Therefore,the total voids volume of 2348 Å3 corresponds to 58 extra mole-cules of water (580e�) or 14.5 molecules per formula unit.

2.7. Thermogravimetric analysis

Thermogravimetric analysis was performed on the powder froma freshly prepared sample of compound 4 without grounding. Thisrevealed a mass-loss step that could be attributed to water re-moval from the voids over the temperature interval 20–120 �C.The loss of 8.2% corresponds to 11 water molecules per formulaunit. DTA shows a phase transformation occurs at about T =120 �C. The powder diffraction analysis for a sample of compound4 after heating to this point depicted an X-ray amorphous phase.

After this, there is a slow mass loss of 2.6% that could be associatedwith the loss of coordinated water molecules, which is then fol-lowed by a permanent mass reduction until the temperaturereaches 580 �C. The latter is most likely associated with thedecomposition of 1,10-phenanthroline molecules. Taking into ac-count the estimative approach of the PLATON calculations, the finalcomposition of (phenH)[{Nd(H2O)2(phen)2}{Re4Te4(CN)12}]�11H2Owas assigned according to the TGA data, which still has a goodcorrelation with the first proposed composition.

3. Results and discussion

The interactions of the cluster compound K4[Re4Te4(CN)12]�5H2O with NdCl3�6H2O in aqueous solutions containing (1) severaldrops of HCl (conc.) to prevent the precipitation of Nd2O3�xH2O or(2) organic agents: hexafluoroacetylacetonate, 2,20-bipyridine or1,10-phenanthroline gave four new crystalline compounds. Theirstructures were studied by single crystal X-ray diffraction analysis(Table 1).

In the structures of all the obtained compounds, the [Re4Te4-(CN)12]4� units have a similar structure as in related compounds[27–33,49]. Namely, the triangular faces of the Re4 tetrahedral clus-ter are coordinated by l3-Te atoms giving a {Re4Te4} cluster core. Inaddition, each Re atom is also coordinated by three cyano ligandsthrough the C atoms. Selected interatomic distances in compounds1–4 are shown in Table 2. These bond lengths are similar to the dis-tances in the starting materials and other related compounds.

3.1. Crystal structure of (H)[{Nd(H2O)5}{Re4Te4(CN)12}]�5.5H2O (1)

The structure of compound 1 refers to the monoclinic crystalsystem (space group P21/c), and all atoms occupy general positions.One Nd3+ cation with its first coordination sphere and one clusteranion form the asymmetric unit. Compound 1 possesses a three-dimensional structure due to the polymeric anion {[{Nd(H2O)5}-{Re4Te4(CN)12}]�}111. Four of twelve CN groups of the clusteranion take part in the connection, whilst each Nd cation is bondedwith CN groups of four cluster anions (Fig. 1). In the frameworkstructure, one can distinguish 1D ribbons oriented along the crys-tallographic a direction and organised as two chains � � �Nd–NC–Re4–CN–Nd� � � connected with each other. The ribbons are shiftedon the half of the translation vector in relation to each other andbonded via CN ligands of cluster anions in the b and c directionsgiving the three-dimensional structure (Fig. 2). In terms of theframework connectivity described in the notation [49], the frame-work-structure of this compound has a (4,4) connectivity.

The coordination polyhedron of the Nd cations is a slightlydistorted tri-capped triangular prism (CN = 9). The bases of thecoordination prism are organised by two N atoms of the bridgingCN ligands and one O atom from a water molecule. The water mol-ecules also cap the faces of the prism (Fig. 2). The C–N–Nd anglesdeviate reasonably from a flat angle and they are equal to141.1(8)–153.4(8)�.

The structure of the framework is rather loose. The SQUEEZEoption of the PLATON program package calculated two voids in theframework structure of 1 located at (�0.087, 1, 0) and (0.099, 1/

Table 2Selected interatomic distances (Å) in compounds 1–4.

1 2 3 4

Re–Re 2.8524(5)–2.8790(5) 2.8597(3)–2.8949(3) 2.8668(3)–2.9103(4) 2.8458(7)–2.8747(9)Re–Te 2.6295(7)–2.6471(7) 2.6234(4)–2.6489(3) 2.6252(3)–2.6484(4) 2.6220(8)–2.6471(9)Nd–O(H2O) 2.454(7)–2.575(6) 2.472(4)–2.472(4) 2.424(5)–2.521(6) 2.451(8)Nd–N(NC) 2.564(8)–2.644(8) 2.571(4)–2.589(4) 2.614(4)–2.634(4) 2.489(11)Nd–N(phen) 2.626(9)–2.633(12)

O.A. Efremova et al. / Polyhedron 31 (2012) 515–523 517


2, 1/2), where each has a volume of 434 Å3. The walls of the voidsconsist of water molecules coordinated to Nd and the nitrogenatoms of the cluster anions. These voids are ideal to contain solvat-ing water molecules. Seven independent positions of oxygen atomsthat belong to the solvating water molecules were observed underthe SHELXL refinement. All the water molecules occupy generalpositions, where three of them are only partially occupied. The to-tal amount of solvating water molecules was calculated to be equalto 5.5 per formula unit. This amount of solvating water is in good

agreement with the potential solvent quantity calculated withPLATON.

The framework of compound 1 has an excess negative charge.No potassium atoms have been observed in the composition ofthe crystalline product by means of the semi-quantitative analyti-cal method EDX. From the reason of the charge balance, we assumethat there is one H+ pattern per formula unit in the structure of thiscompound. The protons should be located in the small voids form-ing H3O+ or other complexes (e.g. Eigen or Zundel cations) with the

b

c

Fig. 2. The (100) projection of the structure of 1 (the ribbons discussed in the text can be observed along the a axis; solvating water molecules are omitted).

ReTeONC

Fig. 1. A fragment of the structure of 1 with the Nd3+ cation shown as the coordination polyhedron.



solvating and/or coordinated water molecules, as it has beenshown previously for the related compound (H)[Lu(H2O)6{Re4-

Te4(CN)12}]�6H2O [41].

3.2. Crystal structure of K2[{Nd(H2O)7}2{Re4Te4(CN)12}2]�8H2O (2)

Compound 2 crystallizes in the monoclinic crystal system(space group C2/c). In the structure (Fig. 3) of the compound, allof the atoms occupy general positions. One Nd3+ cation with itsfirst coordination sphere and one cluster anion form the asymmet-ric unit. There are also two independent positions occupied by

potassium cations. The distance between these two positions isequal to 2.521(5) Å, which is too short to permit their simulta-neous presence. The occupancy of each position was estimated as0.5. The refinement of such a model gave both a reasonable sizeof the thermal ellipsoids for the K atoms and the electroneutralcomposition, i.e. for every cluster anion [Re4Te4(CN)12]4� there isone Nd3+ cation and one K+ cation. This is also in good agreementwith the data obtained from the semi-quantitative analyticalmethod EDX.

Compound 2 represents an ionic structure with two potassiumcations in the cationic part per dimer anion formulated as

a

c

Fig. 3. A packing diagram of the structure of 2 viewed along the b axis (solvating water molecules and K+ cations are not represented).

Fig. 4. A close view on the dimeric anion [{Nd(H2O)7}2{Re4Te4(CN)12}2]2� (the Nd3+ cations are shown as the coordination polyhedra) in the structure of 2.



[{Nd(H2O)7}2{Re4Te4(CN)12}2]2� (Fig. 4). The dimer anion is builtfrom two cluster anions bridged with each other via two cations,[Nd(H2O)7]3+, and has a point symmetry C2 (Fig. 4). Seven watermolecules and two nitrogen atoms of CN ligands are found in thecoordination environment of the Nd3+ cations (CN = 9). The coordi-nation polyhedron of Nd3+ is a slightly distorted tri-capped prism.One base of the prism is formed by two N atoms and one O atom,whereas the other base is formed with three O atoms and threeother O atoms also cap the prism. The C–N–Nd angles once againdeviate reasonably from a flat angle and are equal to 161.3(3)�and 165.3(3)�.

3.3. Crystal structure of K0.5H0.5[{Nd(H2O)5}{Re4Te4(CN)12}]�3H2O (3)

Compound 3 is isotypical to the compounds belonging to thestructural type 2, described in the earlier paper [42]. It crystallizesin the space group Cmcm. The structure of this compound consistsof two-dimensional polymeric anionic layers {[{Nd(H2O)5}{Re4Te4-(CN)12}]�}11 (Fig. 5). The Nd3+ cation and the cluster anion arelocated on mirror planes that are perpendicular to the c and a axesrespectively.

The main difference between the above-mentioned structuraltype 2 and the structure of compound 3 is the coordination polyhe-dron of Nd3+. Namely, in the case of the compounds 2-Ln/Q thecoordination polyhedron is a slightly distorted square antiprismwith the CN being equal to 8, whilst in the case of compound 3the coordination polyhedron of the Nd cation is a slightly distortedone-capped square antiprism (CN = 9). One base of the antiprism isformed by four water molecules, whilst the other base is organisedby four N atoms of the bridging CN ligands. The latter is capped bya water molecule (Fig. 5). The mirror plane perpendicular to the caxis shares the neodymium coordination polyhedron and coincideswith a plane of three O atoms: two from the bottom base and oneat the cap. To put it another way, there are four nitrogen atoms ofcluster anions and five water molecules in the coordination envi-ronment of the Nd3+ cation. This is different from what was foundin the case of Ln3+, where only four water molecules wereobserved.

In terms of the framework connectivity, the layered-structure ofthis compound also has (4,4) connectivity. That means that the 2Dpolymeric structure is organised by every cluster anion, beingbonded with four cationic {Nd(H2O)5}3+ units, and every Nd3+ cat-ion is connected with four cluster anions via the bridging CNgroups. The polymeric sheets have a crimped structure and theyare packed along the ac plane in such a way that the cluster anionslay one over the other (Fig. 6).

Compound 3 also possesses a similar characteristic to the struc-tural type 2 given in the previous paper [42], namely the evidenceof small channels that were found along the c axis. The surface of

Fig. 5. A fragment of the structure of 3 illustrating the square-like arrangement ofthe cluster anions around the Nd3+ cation (the Nd atom is shown as thepolyhedron).

b

c

Fig. 6. The packing of the layers in the structure of 3 viewed along the a axis (solvating water molecules and K+ are not represented).



the channels is formed by the nitrogen atoms from the CN groupsand water molecules coordinated to Nd. The volume of the chan-nels is big enough to incorporate potassium cations and highly dis-ordered solvating water molecules linked with the surface atomsvia hydrogen bonds. According to the X-ray analysis, there are fourpositions of water molecules in the structure of 3, none of which isfully occupied. The total amount of solvating water was deter-mined to be 3 per formula unit. A similar high disordering of thesemolecules was also observed in the other isotypical compounds.This is most likely caused by the ability of the crystals to lose thesolvating water molecules out of the channels straight after theirremoval from the mother liquid.

According to the EDX data there are 0.5 potassium cations performula unit in compound 3. From the SHELXL refinement, wefound out that the K+ cations occupy the positions 8e with sitesymmetry m. Another symmetrically equivalent position of K+ istoo close (3.963(11) Å) for both positions to be fully occupied.The half-occupied position gives 0.5 potassium cations per formulaunit. Once again, we ought to assume that there are 0.5H+ patternsper formula unit in the structure of this compound. That was alsothe case for the 2-Ln/Q compounds, which were described in theabove-mentioned paper [42]. The refinement of such a model gavea reasonable R-factor and the size of the thermal ellipsoids for theK atoms and the composition K0.5(H)0.5[{Nd(H2O)4}{Re4Te4-(CN)12}]�3H2O is in good agreement with the EDX results.

Though the composition of compound 3 is close to that of 1, thestructure of compound 3 differs from the latter dramatically. Incontrast to compound 3, compound 1 has a 3D structure, althoughin both structures the (4,4) connectivity type is realised. The differ-ence arises in the CN groups of the cluster anions that act as bridg-ing groups. In the case of compound 3, four CN groups belonging totwo Re atoms of the cluster core take part in the polymeric struc-ture formation, while the four bridging groups from four differentRe atoms of the cluster core form the polymer in compound 1.

3.4. Crystal structure of (phenH)[{Nd(H2O)2(phen)2}{Re4Te4(CN)12}]�11H2O (4)

Compound 4 crystallizes in the monoclinic crystal system(space group C2/c). Both the Nd containing cationic unit and thecluster anion [Re4Te4(CN)12]4� have the point symmetry 2. Thiscompound has a chain structure due to the polymeric anion{[{Nd(H2O)2(phen)2}{Re4Te4(CN)12}2]�}1. The structure of the poly-meric anion is organised by alternating between the cationic com-plexes {Nd(H2O)2(phen)2}3+ and the cluster anions along thecrystallographic c axis, as is shown in Fig. 7.

Each neodymium atom in the structure of the cationic unit iscoordinated by two water molecules, two N atoms of the CNgroups of the cluster anions and two molecules of 1,10-phenan-throline. The p-systems of both organic ligands are oriented insuch a way that effective p–p stacking between them is possible.The coordination polyhedron of the Nd cation is a slightly distortedtetragonal antiprism, where each tetragonal base is formed by twoN atoms of phen, one N atom from the CN group and one O atombelonging to the coordinated water molecule. The two-fold axisof the cationic unit {Nd(H2O)2(phen)2}3+ goes via the Nd atomand the mid points of the edges connect the O atoms from one sideand the N atoms of phen from the other side (Fig. 7).

In contrast to the previous three compounds where the CN = 9,for the Nd cations in compound 4 the CN of Nd is 8. An analysis ofneodymium complexes with 1,10-phenanthroline deposited in theCambridge Structural Database [50] revealed that CNs of Nd in{Nd(phen)2} units vary from 8 to 10. The individual CN depends onboth steric parameters of the supplemental ligands and the crystalpacking particularities. For instance, in the related cyanobridgedcoordination compounds containing the anions [{Nd(H2O)-(phen)2}2{M0(CN)4(phen)}4]2� (M0 = Os, Ru), each Nd cation iscoordinated by two molecules of 1,10-phenanthroline, one watermolecule and three N atoms of the CN ligands; thus, giving CN = 8[51,52].

The negative charge of the polymeric chains {[{Nd(H2O)2-(phen)2}{Re4Te4(CN)12}2]�}1 in compound 4 should be compen-sated by an additional cation. No potassium cations wereestablished by both SHELXL refinement and semi-quantitativeEDX analysis, but there was one additional molecule of 1,10-phe-nanthroline; thus we propose that the nitrogen atoms of the latterare protonated to give the cation (phenH)+. This cation is disor-dered over two symmetrically equivalent overlapping positionsand each is expected to be half-occupied. The planes of thep-systems of (phenH)+ and one of the coordinated molecules ofthe organic ligand are parallel and located from each other witha distance of �3.2 Å. This distance is typical for aromatic moleculeshaving a p–p stacking interaction.

A remarkable feature of compound 4 is the large channelsformed by the packing of the chains (Fig. 8). The channels areoriented along the crystallographic c axis. The central axes of thechannels have coordinates (1/2, 0, z) and (0, 1/2, z) and passthrough the inversion centres. The channel’s estimated diameteris about 6.2 Å. The total potential solvent volume per unit cell is2348 Å3, corresponding to 32.0% of the unit cell volume. Com-pound 4 presents the second example of a porous structure derivedfrom a tetrahedral cluster with a {Re4Q4} cluster core. In the frame-

a

b

c

Fig. 7. A view of the polymeric anion {[{Nd(H2O)2(phen)2}{Re4Te4(CN)12}]�}1 in the structure of 4 (hydrogen atoms are omitted for clarity and the Nd3+ cation is shown as thecoordination polyhedron).



work of the earlier obtained compound, [Ni(NH3)2(en)2][{-Ni(en)2}3{Re4Te4(CN)12}2]�38H2O, the potential ‘‘guest’’ moleculevolume was calculated to be equal to 2870 Å3 which correspondsto 37% of the unit cell volume [17].

The walls of the large channels in the framework of 4 are deco-rated by hydrophilic N atoms belonging to terminal CN ligands ofthe [Re4Te4(CN)12]� cluster anions from one side and hydrophobichydrogen atoms of 1,10-phenanthroline molecules from anotherside (Fig. 8). Such an unusual feature makes this framework anattractive matrix for the inclusion of amphiphilic molecules or cat-ions (e.g. ROH, RNH2, RNH3

+ etc.) of corresponding size and shapebased on ‘‘host–guest’’ principles. Indeed the powder diffractionstudies of samples left in the air for weeks at room temperatureand after heating under an IR lamp indicates that the original crys-tal structure remains essentially unchanged; however, the full re-moval of water molecules (T = 120 �C) shows the formation of anX-ray amorphous phase.

4. Conclusions

This paper is the first study representing the system Ln3+/poly-dentate ligand/[Re4Q4(CN)12]4� (Q = S, Se, and Te). Our earlier stud-ies have showed that in the system with 3d metal cation/polydentate amine ligand/[Re4Q4(CN)12]4� (Q = S, Se, and Te) thefollowing factors have a crucial influence on the resultant coordi-nation polymer structure: (i) the coordination number of the tran-sition metal cation; (ii) the organic ligand’s denticity; (iii) thecluster core composition and (iv) the reactants ratio (e.g. the metalcation/ligand ratio) [16]. In the current work, we studied the crys-tal structures of four different cluster complexes based on Nd3+

cations and tetrahedral cluster anions [Re4Te4(CN)12]4�. The influ-

ence of the presence of an organic agent in the mother liquor onthe resultant compounds structures was established by theintroduction of three different organic reactants that are able tocoordinate metal cations in a bidentate mode (e.g. hexafluoroace-tylacetonate, 2,20-bipyridine or 1,10-phenanthroline) in the reac-tions. An equimolar ratio of Nd3+ and the respective organicagent was used in order to reveal the influence (if any) of the ratioof Nd cation to ligand on the dimensionality of the resultant coor-dination polymer. Thus, compounds 2, 3, and 4 were obtained fromthe respective reaction mixtures. However, in the case of com-pound 4, the reaction procedure was differently organised.Namely, the solution of the mixture of NdCl3 and 1,10-phenanthro-line were allowed to react slowly with the solution of the clustersalt in a thin glass tube, whilst in the case of compounds 2 and 3all components were mixed at once in aqueous media andevaporated.

To our surprise 1,10-phenanthroline was found in thestructure of compound 4, whilst hexafluoroacetylacetonate and2,20-bipyridine were not observed in the compositions of com-pounds 2 and 3, respectively. A possible reason for that is thesynthetic technique used to obtain compound 4 which differedfrom those used for compounds 2 and 3. At the same time, bothcompounds 2 and 3 have structures and dimensionality that aredifferent from those of compound 1, which was obtained in theabsence of any organic reagent in the reaction mixture, thoughusing similar reaction conditions. Whilst compound 1 possessesa framework structure, compounds 2 and 3 have dimensionalitiesof 0 and 2. This unexpected result makes us think that the impactof the organic ligands on the crystal structures in this case iscaused by either changing the pH in the reaction media or elseby the formation of structure-forming intermediates, where theligands play a role of templates.

In the case of compound 4, 1,10-phenanthroline showed the ex-pected ability to block some of the coordination places around therare earth metal cation. That led to the generation of a chain struc-ture, which differs dramatically from the three-dimensional struc-ture of 1 obtained from a slightly acidic solution in the absence ofany organic agents.

Thus, the current research showed that the presence of organicagents in the reactions of the tetranuclear chalcocyanide rheniumclusters [Re4Q4(CN)12]4� with rare earth metal cations have twokinds of influence: (1) the obtained compounds have a structurethat is different from the one that results from a solution withoutany organic agents in it; the rare metal cations are only coordi-nated by water molecules and the cyanide ligands of the clusteranion. (2) The obtained compound’s structure changes due to thecoordination of the organic ligand to the metal cation.

It worth noticing as well that the structure and composition ofcompound 1 are also completely different from those found for therecently obtained compounds [{Nd(H2O)14/3Cl1/3}3{Re4Q4(CN)12}2]�2H2O (Q = S, Se) [42]. Although all three compounds were obtainedunder similar conditions and possess three-dimensional struc-tures, the connectivity in their structures are different: while it is(4,4) for compound 1, it is (4,6) for the latter two compounds.The influence of the cluster core composition on the crystal struc-ture is obvious from what we have observed here. Such an influ-ence of the cluster core composition has already been observedbefore when the cluster ions [Re4Q4(CN)12]4� form complexes withcopper cations [16,27]. We believe that it is caused by the naturalincrease of both the steric size of the cluster anions and the partialnegative charge on the nitrogen atoms of CN ligands in the rowS–Se–Te.

The present study also showed that an additional factor seemsto be important for the systems with rare earth metal cations,namely, the concentration of H+ or other monocations in the reac-tion mixture. The impact of this factor on the generation of the

Fig. 8. A van der Waals representation of the channel structure of 4 viewed alongthe c axis.



coordination polymers possessing certain compositions and struc-tures still needs rigorous proof.

Acknowledgments

This work was supported by the Russian Foundation for BasicResearch (Project No. 09-03-92004) and GC No. 02.740.11.0628of FFP ‘‘SSESIR 2009-2013’’.

Appendix A. Supplementary data

CCDC 829228, 829229, 829230 and 829231 contain the supple-mentary crystallographic data for the compounds 1–4. These datacan be obtained free of charge via http://www.ccdc.cam.ac.uk/con-ts/retrieving.html, or from the Cambridge Crystallographic DataCentre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected].

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