Polymeric Double [Cu(NCS)] Chains in the Crystal Structure of [Cu2

Polymeric Double [Cu(NCS)] Chains in the Crystal Structure of [Cu

(Me

Ea)

(SCN)

]

(HMe

Ea = 2-Dimethylaminoethanol) (NewPolymorph) and the Dimeric Structure of its DMSO Adduct

Elena A. Vinogradova

, Olga Yu. Vassilyeva

, Volodymyr N. Kokozay

, and Brian W. Skelton

aDepartment of Inorganic Chemistry, National Taras Shevchenko University, Volodimirska st. 64, Kyiv 01033, Ukraine

bDepartment of Chemistry, University of Western Australia, Crawley, Western Australia 6009, Australia

Reprint requests to Dr. Olga Yu. Vassilyeva.

Fax: +380 44 296 2467. E-mail: vassilyeva@chem.univ.kiev.ua Z. Naturforsch.57 b,319–322 (2002); received October 15, 2001 Zerovalent Copper, Amino Alcohol, Polymers

A new polymorph of the copper(II) thiocyanate complex with 2-dimethylaminoethanol, [Cu2(Me2Ea)2(NCS)2]1(HMe2Ea = 2-dimethylaminoethanol, HL)₁, was isolated in the at- tempted synthesis of a mixed-metal complex from zerovalent copper, cadmium oxide and ammonium thiocyanate in CH3CN solution of HL in air. [Cu2(Me2Ea)2(NCS)2(DMSO)2]₂is a product of recrystallization of1from DMSO. X-ray analysis carried out on single crystals for both compounds revealed that1is a rare example of a 1D coordination polymer consisting of two chains in which the metallic centres are connected through single end-to-end NCS groups.

The chains are inter-linked through alkoxo-bridges of L groups between the neighboring copper atoms. Complex₂is a centrosymmetric dimer composed of two CuL(NCS)DMSO units linked by alkoxo-bridges of L groups.

Introduction

Polymorphism – the existence of more than one crystal structure for a given material – has been the subject of increasing interest in recent years [1]. Be- cause the structures of polymorphs necessarily dif- fer, their properties may differ, and the choice of a particular polymorph and selection of these proper- ties (e. g., dissolution rate for a pharmaceutical) for ultimate use depends on one’s ability to consistently obtain the desired polymorph under controlled and reproducible conditions.

This paper reports the structure of [Cu

(Me

Ea)

(NCS)

]

(HMe

Ea = 2-dimethylaminoethanol, HL)

, a polymorph of the copper thiocyanate com- plex with 2-dimethylaminoethanol

[2], and a comparison is made with the structure of the DMSO adduct of

, [Cu

(Me

Ea)

(NCS)

(DMSO)

]

, which is also presented.

Experimental Section

All chemicals were of reagent grade and used as re- ceived. All experiments were carried out in air. Ele-

0932–0776/02/0300–0319 $ 06.00 c^ÿ2002 Verlag der Zeitschrift f¨ur Naturforschung, T¨ubingen^þwww.znaturforsch.com K

mental analyses for metals were performed by atomic absorption spectroscopy, for SCN anion by standard titrimetric methods, and by the Department of Chem- istry, Bath University microanalytical service (for C, H and N). The infrared spectrum was recorded as a KBr disc on a UR-10 spectrophotometer in the 4000 - 400 cm^ÿ1 region using conventional techni- ques.

Synthesis of [Cu2(Me2Ea)2(NCS)2]¹(1)

Copper powder (0.32 g, 5 mmol), CdO (0.32 g, 2.5 mmol), NH4SCN (1.14 g, 15 mmol), CH3CN (10 cm³) and HMe2Ea (4 cm³) were heated to 60^þC and magnet- ically stirred until total dissolution of Cu and CdO was observed (35 min). Dark-green crystals of₁adequate for an X-ray crystallographic study were isolated next day as a first crop(0.39 g). C10H20Cu2N4O2S2(419.52): calcd.

C 28.63, H 4.81, N 13.36, Cu 30.30, SCN 15.25; found C 28.6, H 4.8, N 13.3, Cu 30.3, SCN 15.3%. – IR (KBr):

ÿ = 3100, 2980, 2930 - 2910, 2870, 2190 (CN), 1490, 1470, 1440, 1390 - 1370, 1335, 1280, 1250, 1230, 1180, 1080, 1030, 960, 920, 820 (CS), 790, 710, 560 cm^ÿ1. Re- crystallization of1from DMSO afforded single crystals of [Cu2(Me2Ea)2(SCN)2(DMSO)2]₂.

320 E. A. Vinogradovaet al.· Polymeric Double [Cu(NCS)] Chains

Fig. 1. Fragments of the polymeric chain of₁(a) and_1'(b).

Table 1. Crystal data and structure refinement for₁and₂.

1 2

Formula C10H20Cu2N4O2S2C14H32Cu2N4O4S4

CCDC deposit no. 171601 171600 Formula weight 419.52 575.79 Crystal system orthorhombic monoclinic Space group Pna21 P21/c

a( ˚A) 14.871(2) 9.1227(7)

b( ˚A) 5.9595(8) 12.503(1)

c( ˚A) 17.989(3) 10.7604(8)

þ(^þ) 90 95.288(2)

U( ˚A³) 1594.3(4) 1222.1(2)

Z 4 2

T (K) 150 150

ý(mm^ÿ1) 2.934 2.107

Meas./Indep. Refl. 22487 / 2936 24879 / 6209

Data used 2687 5222

[F> 4.00^ü(F)]

R 0.041 0.024

wR 0.052 0.029

Diffraction experiments were performed on a Bruker SMART CCD diffractometer (^! rotation scans with narrow frames) equipped with graphite monochromated Mo-K^ÿ radiation (^û= 0.71073 ˚A). The data were cor- rected for Lorentz-polarization effects and for the effects of absorption (multi-scan), the non-hydrogen atoms re- fined anisotropically, hydrogen atoms included but not refined. The structure was solved by direct methods and refined by full-matrix least-squares methods on F using the XTAL3.7 program [3]. Relevant crystallographic data are given in Table 1. Bond distances and angles of 2-di- methylaminoethoxo and NCS groups are normal and are given as supplementary material.

Crystallographic data for compounds 1 and 2 have been deposited with the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, UK (fax:

+44-1223-336033; e-mail: deposit@ccdc.cam.ac.uk), and are available on request quoting the deposition num- ber CCDC 171601 and 171600.

Table 2. Selected bond distances ( ˚A) and angles (^þ) for₁*.

Cu(1)-O(11) 1.920(4) Cu(2)-O(11) 1.931(4) Cu(1)-N(14) 2.035(5) Cu(2)-O(31) 1.919(4) Cu(1)-N(21) 1.952(5) Cu(2)-N(34) 2.043(5) Cu(1)-O(31) 1.937(4) Cu(2)-N(41) 1.943(5) Cu(1)-S(23¹) 2.918(2) Cu(2)-S(43²) 2.947(2) O(11)-Cu(1)-N(14) 84.1(2) O(11)-Cu(2)-O(31) 78.1(2) O(11)-Cu(1)-N(21) 170.3(2) O(11)-Cu(2)-N(34) 156.4(2) O(11)-Cu(1)-O(31) 77.9(2) O(11)-Cu(2)-N(41) 99.3(2) O(11)-Cu(1)-S(23¹) 96.0(1) O(11)-Cu(2)-S(43²) 93.7(1) N(14)-Cu(1)-N(21) 95.5(2) O(31)-Cu(2)-N(34) 84.5(2) N(14)-Cu(1)-O(31) 157.0(2) O(31)-Cu(2)-N(41) 170.5(2) N(14)-Cu(1)-S(23¹) 102.8(1) O(31)-Cu(2)-S(43²) 95.6(1) N(21)-Cu(1)-O(31) 99.8(2) N(34)-Cu(2)-N(41) 95.2(2) N(21)-Cu(1)-S(23¹) 93.6(2) N(34)-Cu(2)-S(43²) 103.9(1) O(31)-Cu(1)-S(23¹) 93.3(1) N(41)-Cu(2)-S(43²) 93.6(2)

* Symmetry transformations used to generate equivalent atoms (indicated by superscript).¹x,y– 1,z;²x, 1 +y,z.

Results and Discussion

We have recently succeeded in the preparation of a number of new Cu/M (M = Pb, Co, Zn, Ni) mixed-metal complexes by reacting copper powder with a salt of another metal (or metal oxide and ammonium salt) in a non-aqueous solution of an amino alcohol [4]. However the direct interaction of metallic copper and cadmium oxide with a CH

CN solution of NH

SCN in the presence of HMe

Ea did not result in the desired Cu/Cd mixed-metal com- plex, but afforded

, a polymorph of the reported [Cu

(Me

Ea)

(NCS)

]

[2].

Complex

can be seen as a one-dimensional coordination polymer made of two independent [CuNCS]

chains in which the metal centres are connected through single end-to-end NCS groups.

The chains are interlinked through alkoxo-bridges of L groups between the neighboring copper atoms.

The polymer is displayed in Fig. 1a, showing the

disposition of coordinating L groups to both sides

of the copper / thiocyanate chains. Bridging of

E. A. Vinogradovaet al.· Polymeric Double [Cu(NCS)] Chains 321 Table 3. Selected bond distances ( ˚A) and angles (^þ) for₂*.

Cu-O(1) 1.9290(8) Cu-O(01) 2.2896(8)

Cu-N(4) 2.0275(8) Cu-O(1¹) 1.9391(7)

Cu-N 1.948(1)

O(1)-Cu-N(4) 84.08(3) N(4)-Cu-O(01) 91.75(3) O(1)-Cu-N 159.64(4) N(4)-Cu-O(1¹) 158.45(3) O(1)-Cu-O(01) 97.39(3) N-Cu-O(01) 102.78(4) O(1)-Cu-O(1¹) 76.36(3) N-Cu-O(1¹) 97.35(4) N(4)-Cu-N 97.93(4) O(01)-Cu-O(1¹) 99.58(3)

* Symmetry transformations used to generate equivalent atoms (indicated by superscript).¹1 –x, 1 –y, 1 –z.

thiocyanato ligands is a general phenomenon and has been used successfully in constructing inor- ganic supramolecular architectures based on the Cu

(SCN) structural motif [5]. In the structural chemistry of polymeric copper(II) thiocyanate com- plexes eight-membered Cu(SCN/NCS)Cu arrays, frequently centrosymmetric, are common, as seen,

where dimerization has occurred through bridging of NCS

the axial positions on the copper ions. Recently, the structures of a 1D copper(II) thiocyanate complex consisting of single [CuNCS]

chains [7] and the first one-dimensio- nal heterometallic Cu

/Co

compound containing thiocyanate as bridging ligands [8] have been pub- lished. The topology of [CuNCS]

chains observed in the title compound is uncommon for copper(II) thiocyanate complexes [9] and different from that found in its polymorph

in which copper atoms are alternatively bridged by two oxygen atoms of 2- dimethylaminoethoxo and two thiocyanato groups (Fig. 1b).

The two unique copper centres in

have sim- ilar chemical environment and adopt a distorted square pyramidal coordination (Fig. 1a, Table 2).

The basal plane consists of two bridging oxygen atoms, an amino nitrogen and a nitrogen atom of a NCS group, while the axial coordination site is occupied by a sulfur atom of another thiocyanato group. The two copper atoms are not related by any symmetry operation and separated at 2.9936(9) ˚ A.

The thiocyanato groups are coordinated in a very bent fashion [

Cu(1)-N(21)-C(22): 156.1(5) and

6

Cu(2)-N(41)-C(42): 155.2(5)

].

Coordination of DMSO molecules to copper has a profound effect on the structural properties of

.

Fig. 2. Molecular structure of2.

Complex

is no longer a polymer but a centrosym- metric dimer composed of two CuL(NCS)DMSO units linked by alkoxo-bridges of L groups (Fig. 2).

The copper atom retains its square pyramidal co- ordination geometry formed by donor atoms of 2- dimethylaminoethoxo groups and a nitrogen atom of the thiocyanate group, now terminal, and the oxygen atom of DMSO in the apical position (Ta- ble 3). The Cu

Cu separation of 3.0405(3) ˚ A in

is now only slightly longer.

Cu-N-C 152.82(8)

indicates that the thiocyanate is tilted. Coordina- tion of bulky DMSO molecules on both sides of the [Cu

(Me

Ea)

(SCN)

] unit apparently prevents its propagation through thiocyanate linkages as seen above.

Acknowledgements

The work was in part supported by the Science and Technology Center in Ukraine (Project Gr-32j).

The Royal Society Ex-Agreement Visits – FSU grant (O.Yu.V) is gratefully acknowledged.

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