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Solid State Science 1 (1999) 55-62.

Structure of [Co(NH 3)5CO 3]NO 3•H 2O

J. H. ZHU and H. X. WU

Center for Analysis and Measurement, Fudan University, Shanghai 200433,China

A. LE BAIL

Laboratoire des Fluorures, CNRS ESA 6010, Université du Maine, Facultédes Sciences, Avenue O. Messiaen, 72085 Le Mans Cedex 9, France

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ABSTRACT. — The structure of [Co(NH3)5CO3]NO3•H2O is determinedab initiofrom conventional X-ray powder diffractometry by the direct methods. The cell ismonoclinic, space group P21, Z = 2, a = 7.6733(4) Å, b = 9.6398(5) Å, c = 7.0852(3) Åand β = 106.195(3)°. Refinements by the Rietveld method, lead to RB = 0.053, RP =0.100, and RWP = 0.119. Hydrogen atoms could not be located. Nevertheless a bondingscheme can be proposed for the water molecule linking the isolated [NO3] group to thecarbonatopentamine octahedron through the [CO3] group.

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INTRODUCTION

The coordination compounds of cobalt(III) amine have been widelystudied in the 1950-60’s [1]. They form an enormous number of complexes,but the crystal structures and powder diffraction patterns of many of themremain unknown. We report here the result of a crystallographic

investigation on [Co(NH3)5CO3]NO3•H2O. In absence of single crystal of size suitable for a conventional analysis, the structure was solvedab initiothrough powder diffractometry, using conventional X-ray data. Thecompound was selected as sample I for the "Structure Determination byPowder Diffractometry Round Robin " (SDPDRR) [2]. Although 70participants downloaded the data, no structure proposition was obtained,

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indicating the difficulty level of this work (2 correct solutions were receivedfor the pharmaceutical sample II).

EXPERIMENTAL

[Co(NH3)5CO3]NO3•H2O was prepared according to the methodpublished by Basolo and Murmann [3]. Very small pink crystals wereobtained. The composition of this compound was originally suggested to be[Co(NH3)5CO3]NO3•1/2H2O by Basolo and Murmann and our chemicalanalysis, according to this formula, seemed satisfying (calcd. : NH3, 30.95 ;Co, 21.42 ; found : NH3, 30.62 ; Co, 21.31%). TGA did not revealed a well-defined water departure but the crystal structure determination led toconclude later to a monohydrate instead of a hemihydrate.

Several X-ray powder patterns were recorded. Pattern A was collected on

a Rigaku D/max-rB diffractometer (CuKα ; flat graphite monochromator ;goniometer radius : 185 mm ; rotating anode, 40 KV, 120 mA ; receivingslit (RS) : 0.15 mm ; divergence slit (DS) : 0.5° ; soller slit acceptance angle(SS) : 0.5°; angular range : 10-120°(2θ ) ; counting time : 30 s by steps of 0.02°(2θ ) ; T=25±1°C ; no sample rotation). The vertically mounted samplewas highly packed leading to a very strong preferred orientation but thispattern presents the best resolution with full width at half maximum(FWHM) larger or equal to 0.12°(2θ ). In fact, an obvious anisotropic linebroadening effect was detected. Pattern B was collected on a Siemens D501diffractometer (conventional X-ray fine focus tube, CuKα ; curved graphite

monochromator ; goniometer radius : 200.5 mm ; 38 KV, 28 mA ; RS :0.05° ; DS : 0.3° ; SS : 2°; angular range : 10-120°(2θ ) ; counting time: 24 sby steps of 0.02°(2θ ) ; T=25±1°C ; no sample rotation). The horizontallymounted sample (40 x 20 mm) was prepared according to the McMurdiemethod [4], using a side-loaded sample holder. This way, the preferredorientation was considerably reduced but not completely, FWHMs≥0.13°(2θ ). Pattern C was measured in similar condition as pattern B (exceptRS : 0.15° ; DS : 1° ; 28 s/point) but the sample was dusted on the holderthrough a 63µm sieve. In this way, the preferred orientation was at itsminimum, but that pattern has the lowest resolution with FWHMs≥

0.25°(2θ ). The 3 powder patterns are compared in Figure 1. The powderdiffraction data are reported in Ref. [5].

During the course of this study, testing the compound possible acentricitywas necessary. An incident beam of 40 ps pulse width, 10 Hz repetition

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structure factor extraction. The background was estimated manually withthe DMPLOT program [11]. A total of 780 structure factors “|F obs |” wereextracted by the Le Bail method [12] (iterating the Rietveld [13]decomposition formula) using the program FULLPROF [14]. Then, thedirect methods (SHELXS-97 program [15]) were applied to various reduceddata sets (excluding reflections overlapping too much). The P21 /m space

group could not lead to any coherent result. A meaningful partial model,including Co and 9 other atoms, was identified when using the P21 spacegroup. Several cycles of Rietveld refinements and Fourier syntheses (usingSHELX-76), revealed the whole structure. Hydrogen atoms were notlocated. At least the positions of the water hydrogen atoms may be guessedfrom an evident O-H...O bonding scheme. To be noted is the anisotropicbroadening which affects particularly the patterns with best resolution (Aand B). The 0k0 reflections are the narrower and were fitted separately byintroducing a pseudo two-phase system. The preferred orientation effect inthe A and B patterns seems to correspond to several orientations including

[100] and [010]. The best fit with structure constraint (although never asgood as for pattern C), is obtained from the choice of the [001] directionleading to a March-Dollase [16] parameter value much larger than 1(indicating that the preferred orientation is all but the [001] one, suggestingneedles with the [001] direction as long axis). The final atomic coordinatesand thermal parameters are reported in Table I. Selected interatomicdistances and angles are listed in Table II. The diffraction pattern plot andresidual errors are shown in Figure 2.

Fig. 2 - Rietveld plot for[Co(NH3)5CO3]NO3•H2O.

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TABLE I. Atomic coordinates and thermal parameters for [Co(NH3)5CO3]NO3•H2O.Measurement, refinement conditions and R factors are also given.

Atom x y z B(Å2)

Co 0.8192(5) 0.2500* 0.4408(4) 2.39(7)N(1) 0.258(2) 0.883(2) 0.802(2) 1.3(2)N(2) 0.264(2) 0.895(2) 0.374(2) 1.3(2)N(3) 0.893(2) 0.113(2) 0.271(3) 1.3(2)N(4) 0.433(2) 0.662(2) 0.636(2) 1.3(2)N(5) 0.899(2) 0.119(2) 0.668(3) 1.3(2)O(1) 0.081(2) 0.351(2) 0.537(2) 3.3(2)C 0.210(3) 0.280(3) 0.557(3) 3.3(2)O(2) 0.260(2) 0.156(2) 0.620(2) 3.3(2)O(3) 0.343(2) 0.369(2) 0.540(2) 3.3(2)N(6) 0.195(3) 0.300(2) 0.033(3) 4.2(2)O(4) 0.350(2) 0.378(2) 0.036(2) 4.2(2)O(5) 0.200(2) 0.177(2) 0.106(2) 4.2(2)O(6) 0.057(2) 0.376(2) 0.023(2) 4.2(2)Ow 0.588(2) 0.148(2) 0.886(2) 1.6(3)

Cell parameters a = 7.6733(4) Å, b = 9.6398(5) Å, c = 7.0852(3) Å

andβ = 106.195(3)°Space group and Volume P21 503.3Å3

Calculated density 1.87 g•cm-3

Atomic coordinates refined 44Zeropoint (°2θ ) 0.007(2)Profile parameters U = 0.250,V = -0.268(5),W = 0.113(2)Discrepancy factors† RB= 0.053, RP= 0.100, RWP= 0.119, REXP= 0.040

* arbitrarily fixed origin †background subtracted

STRUCTURE DESCRIPTION AND DISCUSSION

A projection of the crystal structure of [Co(NH3)5CO3]NO3•H2O nearlyalong thec axis is shown in Figure 3. The title compound containsunidentate carbonate ions [Co(NH3)5CO3]+. Searching literature, the onlyother carbonato-amine-cobalt-nitrate-hydrate, of which the structure wasdetermined, is the tetramine {[Co(NH3)4CO3]NO3}2•H2O [17], containingbidentate carbonate ions. Other carbonatopenta-amine-cobalt(III)-hydrates

are known with bromine [18] or iodine [19] in place of the nitrate group.[Co(NH3)5CO3]•Br•H2O is also acentric (space group Pna21), whereas[Co(NH3)5CO3]•I•H2O is not (space group P2/c). One can find also a SO3group in place of CO3 in [Co(NH3)5SO3]•Cl•H2O [20], centric as well(space group P21 /c), but the S atom is part of the cobalt coordination,forming a [CoN5S] octahedron.

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TABLE II - Selected interatomic distances (Å) and angles (°) for[Co(NH3)5CO3]NO3•H2O.

[CoN5O] octahedron - <Co-(N,O)> = 2.07 Å

Co N(3) N(5) N(4) N(1) N(2) O(1)N(3) 1.97(2) 2.80(2) 2.80(2) 2.85(2) 4.10(3) 3.07(2)

N(5) 89(1) 2.00(1) 2.87(2) 4.10(4) 2.92(2) 2.92(2)N(4) 88(1) 90(1) 2.04(1) 2.94(2) 2.97(2) 4.21(2)N(1) 89(1) 177.8(3) 90(1) 2.10(1) 3.05(2) 3.03(2)N(2) 178.9(2) 90.0(1) 91(1) 92(1) 2.13(1) 2.91(2)O(1) 95(1) 89(1) 176.1(9) 90(1) 85(1) 2.17(1)

[CO3] group - <C-O> = 1.28 Å [NO3] group - <N-O> = 1.32 Å

C O(1) O(2) O(3) N(6) O(6) O(5) O(4)O(1) 1.18(3) 2.31(2) 2.01(2) O(6) 1.27(2) 2.21(2) 2.23(2)O(2) 138(3) 1.30(3) 2.27(2) O(5) 119(2) 1.28(3) 2.38(2)O(3) 104(3) 117(3) 1.37(3) O(4) 112(3) 124(2) 1.41(2)

Water molecule - <Ow-O> = 2.68 Å

O(4)-Ow-O(2) 104.4(0.9) Ow-O(4) 2.67(2) Ow-O(2) 2.69(2)

Fig. 3 - Projection of the crystal structure of [Co(NH3)5CO3]NO3•H2O along thec axis.

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Comparing interatomic distances and angles in the pentamine (Table II)and in the tetramine [17] (Co-O = 1.896 to 1.916 Å ; Co-N = 1.942 to 1.969Å ; C-O = 1.222 to 1.322 Å ; O-C-O angles between 110.3 and 124.8° ; N-O = 1.218 to 1.243 Å and O-N-O angles between 118.4 and 121.7°), amuch large dispersion of those values is observed in the former. In fact,some values are really out of the expected ones. Accordingly, it may be

suggested that the accuracy of the present study is an order of magnitudelower than the single crystal study. Indeed, it was possible to constrain theinteratomic distances in the pentamine so as to stay in the same range as inthe tetramine, whereas the reliability factor RB increased by 0.3%, and RPand RWPby only 0.1%. It would have been certainly possible to improve thequality of our result if preferred orientation could have been avoided,allowing to make the refinement from powder patterns with a much betterresolution (by a factor 2). Nevertheless, the structure is grossly established,and the water bonding scheme can even be proposed with confidence due totwo short Ow-O(2) and Ow-O(4) distances (both ~2.68 Å) and an ideal

O(4)-Ow-O(2) angle (Table II), the next neighbor being N(3) at 3.08 Åfrom the water molecule. Thus, the water molecule links the isolated [NO3]group to the [CO3] group (fig. 3). A quite complex hydrogen bondingscheme was established in the tetramine compound, for which the aminehydrogens were shown to be involved in significant interactions with thenitrate oxygens and water of crystallization although generally weaker thanthose of the carbonato oxygens. Establishing the amine hydrogen bondingscheme is not possible here.

Interest in cobalt amine complexes is still alive. Some are known topromote the hydrolysis of ATP to ADP [21], or may induce DNAconformational changes [22]. The present structure determination was astep needed for further investigations. Why no participant succeeded insolving the structure during the SDPD Round Robin is probably because theproblem complexity is near of the feasibility limit due to low-resolutiondata (see also other comments by D. Bradley [23]). From synchrotronradiation with minimal FWHM as low as 0.01-0.03°(2θ), and similarwavelength, using a capillary in order to avoid preferred orientation, thedifficulty would not have really existed (but intrinsic line broadening wouldhave precluded to attain the minimal line widths).

REFERENCES

[ 1]Gmelins Handbuch der Anorganischen Chemie , 58 Cobalt, part B, Verlag Chemie(1964).

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[ 2] A. LE BAIL and L.M.D. CRANSWICK,Structure Determination by Powder Diffractometry Round Robin , 1998, http://www.cristal.org/SDPDRR/ [ 3] F. BASOLO and R.K. MURMANN, Inorg. Synth ., 1953,4, p. 171.[ 4] H.F. McMURDIE, M.C. MORRIS, E.H. Evans, B. PARETZKIN and W. WONG-NG,Powder Diffraction , 1986,1, p. 40.[ 5] H. WU, J. ZHU, L. MA, X. SHEN and G. SHI,Powder Diffraction , 1998,13 , p. 32.[ 6] P.E. WERNER, L. ERIKSSON and J. WESTDAHL, J. Appl. Crystallogr ., 1985,18 ,

p. 367.[ 7] P.M. DE WOLFF, J. Appl. Crystallogr ., 1968,1, p. 108.[ 8] G.S. SMITH and R.L. SNYDER, J. Appl. Crystallogr ., 1979,12 , p. 60.[ 9] J.W. VISSER, J. Appl. Crystallogr ., 1969,2, p. 89.[10] A. BOULTIF and D. LOUËR, J. Appl. Crystallogr ., 1991,21 , p. 987.[11] H. MARCINIAK, DMPLOT : Program for Viewing Results of Rietveld Analysis ,Version 3.47, High Pressure Research Center, Warsaw, Poland, 1995.[12] A. LE BAIL, NIST Special Publication , 1992,846 , p. 213.[13] H.M. RIETVELD, Acta Crystallogr ., 1967,22 , p. 151 and J. Appl. Crystallogr .,1969,2, p. 65.[14] J. RODRIGUEZ-CARVAJAL, in "Collected Abstracts of Powder DiffractionMeeting", Toulouse, France, July 1990, p. 127.[15] G.M. SHELDRICK,SHELX-97 Program , Univ. of Göttingen, Germany (1997).[16] W.A. DOLLASE, J. Appl. Crystallogr ., 1986,19 , p. 267.[17] I. BERNAL and J. CETRULLO,Struct. chem ., 1990,1, p. 227.[18] H.C. FREEMAN and G. ROBINSON, J. Chem. Soc ., 1965, p. 3194.[19] H. NAKAI, Y. KUSHI and H. KUROYA, Nippon Kagaku Zasshi , 1967,88 , p. 1126.[20] R.C. ELDER, M.J. HEEG, M.D. PAYNE, M. TRKULA and E. DEUTSCH, Inorg.Chem ., 1978,17 , p. 431.[21] F. TAFESSE, S.S. MASSOUD and R.M. MILBURN, Inorg. Chem ., 1993,32 ,p. 1864.[22] C. BAUER and A. H.-J. WANG, J. Inorg. Biochem ., 1997,68 , p. 129.[23] D. BRADLEY, "X-raying the Web",The Alchemist , 1998,http://www.chemweb.com/alchem/alchem98/catalyst/ctold/ct_980911_xray_full.html