This work has been digitalized and published in 2013 by Verlag Zeitschrift für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution4.0 International License.

Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschungin Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung derWissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht:Creative Commons Namensnennung 4.0 Lizenz.

The Crystal Structure of Lithium /ac-Triaquatrisulfitorhodate(III)hydroxide, Li4[Rh(S03)3(0 H 2)3](0H )Andreas Mäurer, Dietrich K. Breitinger*, and Roman Breiter Institute o f Inorganic Chemistry, University o f Erlangen-Nürnberg,Egerlandstraße 1, D-91058 ErlangenZ. Naturforsch. 48b, 1187-1192 (1993); received May 10, 1993

Sulfitorhodates(III), /ra/w-Influence, Network, Layer Structure/ac-L i4[R h(S03)3(0 H 2)3](0H ) crystallizes in the rhombohedral space group R 3-C 34, Z = 1,

in trigonal setting a = 807.7(2), c = 1339.0(3) pm, V = 756.6(2)-106 pm3, Z = 3. Rh is octahe- drally coordinated by three facial S-bonded sulfite groups with R h -S = 222.6(1) pm and three aqua ligands with R h -O bonds R h -O = 217.5(3) pm, elongated by a /raos-influence. The average S -O bond length is 148.0(3) pm. All hydrogen atoms have been located. The OH" ion is coordinated exclusively to Li+. The anions are held together by Li+ cations in octahedral environment and by hydrogen bonds o f medium strength. Alternatively, the structure can be considered to be built o f packages o f two oxygen nets and a metal layer, stacked in a sequence similar to that in the CdCl2-structure.

1. Introduction

Our studies of sulfito complexes of platinum- group metals have provided evidence for the strong /raws-influence of the S-bonded S 0 3-ligand. This influence has been proved for square-planar Pd(II) and Pt(II) centers [1] and also for a few oc­tahedral Rh(III) [2] and Ru(II) [3] complexes. In the latter case the J/wis-influence is diminished on peripheral O-protonation [4-6].

On the whole there is only little structural data available for sulfitorhodates, because they tend to form amorphous - S - O - bridged polymers, ase.g. in K 3[Rh(S03)3]-2H 20 . Up to now studies of the bonding situation around the rhodium center were mainly based on vibrational spectroscopy [7].

However, it was possible to synthesize fac- Li4[Rh(S03)3(0 H 2)3](0H ) (1), to grow single crys­tals and to solve the crystal structure of 1. The geo­metrical data were used in the normal coordinate treatment of the anion [8].

2. ExperimentalPreparation o f Li4[R h (S O 3) 3(O H 2) 3](O H ) (1)

S 0 2 was slowly bubbled into a stirred solution of 0.273 g (1.00 mmol) RhCl3-3.5H20 and 0.443 g (6.00 mmol) Li2C 0 3 in 100 ml H 20 at room tem­perature. On neutralization to pH 7 the dark violet

* Reprint requests to Prof. Dr. D . K. Breitinger.Verlag der Zeitschrift für Naturforschung,D-72072 Tübingen0932-0776/93/0900-1187/$ 01.00/0

solution turned orange to yellow. Light yellow mi- cro-crystals of Li4[Rh(S03)3(0 H 2)3](0H ) were ob­tained by slow evaporation of water. - Yield:0.410 g (92.8%).

Analysis of metals with photometrical methods: Li by flame photometry and Rh by UV/VIS-

spectrometry as [RhCl6]3~ (Acx = 273.5(5) nm) [9].H 70 13Li4RhS3 (441.92)Calcd H 1.60 Li 6.28 S 21.76 Rh 23.29%, Found H 1.63 Li 6.3 S 21.47 R h 2 3 .5 % .

Single crystals for X-ray structure analysis were obtained by diffusion of acetone into an aqueous solution via the gas phase.

The dried crystals are stable to air. Magnetic measurement confirms the oxidation state Rh(III). The density was determined in dibromomethane with a pyknometer (Table I).

Table I. Crystal data o f Li4[R h(S03)3(0 H 2)3](0H ).

Molecular weight M 441.92 gm ol 1Space group R 3-C 34a 807.7(2) pmc 1339.0(3) pmy 120Cell volume V 756.6(2)-106 pm3Density calcd. 2.910(1) g e m '3Density obs. 2.896(6) g cm-3

Collection and reduction o f dataThe space group was determined on the basis of

Weißenberg (CuKa radiation, I = 154.06 pm) and precession photographs (MoKa, A = 70.93 pm). Re­fined lattice parameters (Table I) were calculated by least-squares refinement (program GIVER [10])

1188 A. Mäurer et al. • Lithium /ac-Triaquatrisulfitorhodate(III)hydroxide

Single crystal diffractometer Philips PW 1100Crystal size 0.13 0.14 0.17m m 3^(A gKJ 56.014 pmLinear absorption coefficient n 11.21 cm-1Range o f diffraction angle 9 2 .5 -30°s in ÖmaxM 9 .3 2 -10“3 pm-1h k l range ±14, ±14, 23Standard reflections 110, 101,012, 024Standard instability < 0 .0 1 5Scan mode co-scanScan width 1.0 + 0.2 tan#Scan speed 0.15 °s - 'Temperature 293 KNumber o f measured reflections 3085Observed independent reflections 1002

with I > 3 crl 973Internal R -\alue 0.0314F(000) 648Ratio reflexes/parameters 973/67 = 14.5/^-values on F, w = 0.5851/cr2(Fo) R = 0.0286, R h = 0.0232Maximum shift/e.s.d. in the last cycle 0.002Maximum residual electron density 0 .14e- Ä “3Minimum residual electron density -0 .1 4 e~ Ä -3

Table II. Data collection and reduction, struc­ture solution and refinement.

from 28 reflections of a Guinier photograph. In­tensity data were collected with a Philips PW 1100 diffractometer. The structure refinement was based on lattice parameters calculated from 25 single crys­tal reflections in the range 11 .5°< #< 16.5°. They deviate slightly, but not significantly from the powder data:

Rhombohedral setting a = 645.1(3) pm, a = 77.46(1)°, V = 251.8(4) -106 pm3; trigonal setting a = 807.2(4), c = 1338.1(6) pm, V = 755.2(6)-106 pm3. The rhombohedral reflection condition (tri­gonal setting: - h + k +1 = 3 n) was verified. The in­tensity of other reflections is below 1.2 e.s.d.’s.

Detailed measurement conditions are given in Table II.

With respect to the low absorption coefficient (Table II) no absorption correction was applied.

LP-correction and data reduction were per­formed using the CRYSTAN program system [11].

Structure solution and refinementThe structure was solved by Direct Methods

and Patterson syntheses with SHELXS-86 [12]. Rh, S, O atoms were refined (SHELX-76 [13]) an- isotropically; Li and H atoms (the latter positions found from weighted difference Fourier syntheses) were treated isotropically. A refinement with ani­sotropic Li 2 yielded the same atomic coordinates, with the thermal ellipsoid compressed normal to the short L i2 - 0 5 bond; nevertheless the equiva­lent isotropic displacement factor did not decrease

with respect to the isotropic one. The final atomic coordinates and equivalent displacement factors are given in Table III. Table IV summarizes bond distances and angles.

During the refinement an empirical isotropic ex­tinction correction (SHELX76) was applied, but it was abandoned later on, because the parameters did not change significantly*.

* Further details may be obtained from: Fachinforma- tionszentrum Karlsruhe, Gesellschaft für wissenschaft­lich-technische Information mbH, D-76344 Eggen- stein-Leopoldshafen, by quoting the Registry-No. CSD 57642, the names o f the authors and the journal citation.

Table III. Atomic coordinates and equivalent isotropic displacement factors (trigonal setting).

Atom X y z U eq/pm2*

Rh 0 0 0 87(1)S 0.2588(2) 0.0681(2) 0.9103(1) 145(3)O l 0.2384(4) 0.0943(4) 0.8020(2) 227(7)0 2 0.2969(4) -0.0923(4) 0.9229(2) 299(8)0 3 0.4177(4) 0.2462(4) 0.9516(2) 227(7)0 4 0.0583(5) -0.1749(5) 0.1016(2) 203(7)H I 0.1308(21) -0.1033(21) 0.1477(19) 418(22)+H 2 -0.0577(21) -0.2649(21) 0.1166(21) 865(22)+0 5 0 0 0.4166(4) 245(8)H 3 0 0 0.4612(20) 328(22)+L il 0 0 0.7106(9) 243(16)+Li 2 0.4189(14) 0.2802(14) 0.6892(9) 746(18)+

* U eq = 1/3(U33 + l/sin2y(U n + U 22 + 2 U 12cosy)) [14]: + isotropic.

A. Mäurer et al. • Lithium /aoTriaquatrisulfitorhodate(III)hydroxide________________________________________1189

Table IV. Bond lengths (pm) and angles (°) with e.s.d.’s.

Complex anion:R h -SR h - 0 4S - O lS - 0 2S - 0 3

222.6(1)217.5(3)148.5(3)148.2(3)147.4(3)

S - R h - S d0 4 - R h - 0 4 cR h - S - O lR h - S - 0 2R h - S - 0 3

93.7(0)85.0(1)

113.8(1)107.6(1)106.9(1)

0 4 - R h - S0 4 - R h - S d0 2 - S - 0 30 3 - S - 0 1 0 2 - S - 0 1

90.9(1)90.0(1)

110.5(2)109.3(2)108.8(2)

Aqua ligand and hydrogen bonding:0 4 - L i 2 a 211.2(11) R h - 0 4 - L i 2 a 110.8(8)0 4 - H 1 —0 2 ad 0 4 c- H 2 - 0 1 ac 0 4 c- H 2 - 0 2 ad 0 4 c—H 2 - 0 3

270.2(4)283.9(4)296.7(4)277.1(4)

Li 1 0 6 octahedron:Li 1 - O 1f L i l - 0 3 M

207.7(7)215.5(8)

O 1 -L i 1 -O lc0 3 bd- L i - 0 3 be

88.8(4)90.4(4)

O 1 - L i —0 3 “ O l - L i - O S 1*

88.7(3)92.1(4)

Li 2 0 6 octahedron:L i 2 - 0 5 aL i 2 - 0 4 bL i 2 - 0 1 fL i 2 - 0 3 bdL i 2 - 0 2 bL i 2 - 0 2 bcg

199.6(11)211.2(11)211.4(11)217.9(13)227.1(12)250.4(12)

0 5 a- L i 2 - 0 4 b0 5 a- L i 2 - 0 1 f0 5 a- L i 2 - 0 3 bd0 5 a- L i 2 - 0 2 b0 5 a- L i 2 - 0 2 bcg

96.9(4)97.0(5)

175.7(5)89.4(6)83.1(6)

Coordination o f O H - :L i2b—0 5 H 3 - 0 5

199.6(11)59.7(26)

H 3 - 0 5 - L i 2 bLi2b- 0 5 - L i 2 bc

114.0(4)104.6(4)

Symmetry operations:a x+ 2 /3 ,_y+ 1/3, z + 1/3 bx + 1/3 ,7+ 2 /3 , z+2/3 c ~y. x —y, z d y ~ x , - x , ze x + l , y + l , z adjacent anion/cell f x , y , z + 1 adjacent anion/cell g x, y - 1, z adjacent anion/cell

3. Results and Discussion

The structure consists of complex anions fac- [R h(S03)3(0 H 2)3]3~ (Rh in position 0,0,z with z set to zero) linked by Li+ cations (z~ 0) to form layers perpendicular to the c-axis which in turn are con­nected by covalent S -O bonds and O - H - O hy­drogen bonds of medium strength.

The structure can also been considered to con­sist of two different quasi-parallel nets of oxygen atoms between which the metal atoms are interca­lated.

Coordination o f the O H anion

The hydroxide anion (special site) is very strong­ly coordinated to three L i2+ (general site) span­ning the trigonal basis of a O H Li23 tetrahedron. Considering the over-all coordination of Li2+ this special 0 5 atom forms the common corner of three edge-sharing distorted L i2 0 6 octahedra. The L i - 0 5 distance of 199.6(11) pm (octahedral L i0 6) is almost comparable to L i-O = 196.3 pm in LiOH [15] (tetrahedral L i0 4 coordination!).

The proton is not involved in hydrogen bonding since the distance to the nearest O atoms is too far

1190 A. Mäurer et al. ■ Lithium /ac-Triaquatrisulfitorhodate(III)hydroxide

for formation of a (trifurcated) hydrogen bond ( 0 5 - 0 3 = 322.5(5) pm; H 3 - 0 3 = 275(2) pm). Independently, the high frequency v(OH) 3543 cm“1 precludes a hydrogen bond.

The connection pattern around the OH~ ion thus reminds of that in brucite Mg(OH)2.

The complex anion

Figure 1 shows an ORTEP plot [16] of the com­plex anion down [0001]. For bond lengths and an­gles see Table IV.

The R h -O bond R h -O = 217.5(3) pm is signif­icantly longer than the R h -O bond length in the [Rh(OH2)6]3+ ion, which is not affected by the fra/M-influence. For the latter R h -O distances of 200-204 pm are usually found, e.g. in CsRh(S04)2- 12HzO 201.6(3) pm [17], in CsRh(Se04)2 12H20 200.4(3) pm [18] and for [Rh(OH2)6]3+ in rhodium(III) perchlorate solution 204(1) pm [19-21].

In [R h(0H 2)6](C104) • 3 H20 [22] an unusually long R h -O bond of 213.2(6) pm (averaged) is thought to be caused by a rigid H 20/C 104~ frame­work (see discussion in [22]).

The determined distance equals or exceeds R h -O bond lengths trans to phosphine ligands [23,24], which suggests a similar or even stronger /raws-influence of the S-bonded S 0 3 group.

Fig. 1. The complex an ion /ac-[R h(S03)3(0 H 2)3]3 down [0001] (ORTEP [16]).

Fig. 2. Perspective view o f the trigonal cell (SCHAKAL [26]).

A relatively strong bond to L i2+ completes the tetrahedral surrounding of the aqua oxygen 0 4 . This additional coordination to L i2+ could also assist in lengthening of the R h -O bond, cf. the bond-valence method of Brown [25]. The medium- strong hydrogen bond O - H 1 • • • O 2 with O • • • O =270.2 pm aligns the aqua ligand, as given in the perspective view of the trigonal cell (Fig. 2). The H 2 atom resides in a local potential-minimum, within a trifurcated hydrogen bond to O 1 and O 2 of different S 0 3-groups in an adjacent anion and to 0 3 of the same anion (intramolecular H-bond). One of them is shown in Fig. 2. All intermolecular hydrogen bonds link [Rh(S03)3(0 H 2)3]3" anions coarsely along the rhombohedral axes and thus provide a connection between the layers.

As to the R h -S bond length of 222.6(1) pm, there is little comparable data. In trans- N a[R h(S03)2en2] • 3 H 20 [2] the R h -S distance is increased to 232.3(1) pm by the mutual trans-'mfhi- ence. This 10 pm difference between cis- and trans- disulfitorhodates(III) exceeds the 6 -8 pm found for cobaltates(III) [27]. The present strong R h -S bond is shorter than bonds in Rh(III) DMSO com­plexes [28,29]. Along with the short R h -S bond there are remarkably strong S -O bonds of 147.4(3)-148.5(3) pm, taking into account that they are acceptors of hydrogen bonds and also do­nors in coordination to Li+ cations. The S -O

A. Mäurer et al. ■ Lithium /ac-Triaquatrisulfitorhodate(III)hydroxide 1191

bond lengths are of course influenced by being fur­ther involved in dative bonding; thus the shorter S - 0 3 bonds are tied up with longer 0 3 - L i + dis­tances (Table IV).

At the octahedral RhS30 3 center the S - R h - S angles are increased by electrostatic repulsion of the S 0 3-groups, with consistently reducedO - R h - O angles. (The small difference in theO - R h - S angles shows the very small torsional angle between the RhS3- and the R h 0 3-frag- ments.) Also for electrostatic reasons, the S 0 3 li­gands are tilted off the threefold axis, such that the angle R h - S - O l is the biggest among the R h - S - O angles. As a consequence the S - O l bond is directed almost parallel to the c-axis. ThisS - O l bond supplies a covalent link between the oxygen nets of adjacent layers, besides the men­tioned hydrogen-bond links.

Formation o f networks

Figure 3 shows the trigonal layer around the0 ,6-plane with Rh at z = 0, Li 1+ and L i2+ slightly higher (z = 0.0439 and z = 0.0225, repectively), the latter being bonded to 0 5 (z = 0.0833 ~ 1/12) above th a ,6 -plane.

The set of oxygen atoms with z = 1/12 (0 5 , 0 4 and O 1 of the next anion layer) may be considered as a slightly puckered 6-connected net (36 net) of partly distorted triangles (cf. Wells [30]). 4 out of the 14 triangles of this net in the section limited by the unit cell (unit area) form one face each of an octahedron around the Li+ cations.

A regular triangle defined by the three fa c aqua oxygens is one face of the coordination polyhe­dron around rhodium, which is part of the metal layer at z = 0 (see above).

Opposite to this layer another set of the oxygen atoms 0 2 , 0 3 forms a 5-connected net of 8 trian-

Fig. 3. Projection o f the trigonal cell down [0001] and formation o f O-nets (SCHAKAL [26]).------- : Net o f oxygens 0 1 , 0 4 , 0 5 a tz = 1/12.-------: Net o f oxygens 0 2 , 0 3 at z = -1 /1 2 .

gles and one hexagon per unit area. Inside the hex­agon resides the RhS3-pyramid. If this fragments were replaced by a single oxygen atom a complete6-connected net would result.

The described sequence of a 6-connected O-net, a layer of metals and a 5-connected O-net, and the stacking of these packages along the trigonal c-axis resembles the arrangement of the layers in the CdCl2-structure.

There is also a group theoretical relationship of the space group of the CdCl2-structure (R3m ) and the space group of the present structure R 3(descent in symmetry in two steps: R 3m ----->R 3 - ^ R 3 ) .

The authors thank Prof. Dr. K. Brodersen, Er­langen, for laboratory facilities and the Verband der Chemischen Industrie, Fonds der Chemischen Industrie, Frankfurt, for continuous support.

1192 A. Mäurer et al. ■ Lithium /ac-Triaquatrisulfitorhodate(III)hydroxide

[1] D. K. Breitinger and M. Vogt, J. Mol. Struct. 174, 423 (1988), and references therein.

[2] G. Petrikowski and D. K. Breitinger, Acta Crystal­logr. C41, 522 (1985).

[3] R. Breiter and D. K. Breitinger, Z. Naturforsch. 48 b, to be submitted (1993).

[4] D. A. Johnson, D. Y. Jeter, and A. W. Cordes, Acta Crystallogr. C43, 2001 (1987).

[5] S. M. Condren, A. W. Cordes, and B. Durham, Acta Crystallogr. C46, 889 (1990).

[6] D. K. Breitinger and R. Breiter, Z. Naturforsch. 45 b, 1651 (1990).

[7] J. P. Hall and W. P. Griffith, Inorg. Chim. Acta 48, 65(1981).

[8] A. Mäurer and D. K. Breitinger, in W. Kiefer, M. Cardona, G. Schaack, F. W. Schneider, and H. W. Schrötter (eds): Proc. o f the XHIth Interna­tional Conference on Raman Spectroscopy, pp. 330 f., Wiley, London (1992).

[9] A. Mäurer, Ph. D. Thesis, Erlangen (1993).[10] K. Krogmann, GIVER, Fortranprogramm zur Ver­

feinerung von Gitterkonstanten, Karlsruhe (1980).[11] H. Burzlaff, R. Böhme, and M. Gomm, CRYS-

TAN , A Crystallographic Program for M inicom­puters, Universität Erlangen-Nürnberg (1986).

[12] G. M. Sheldrick, Programm-System SHELXS-86, Göttingen (1986).

[13] G. M. Sheldrick, SHELX-76, Program for Crystal Structure Determination, University o f Cambridge (1976).

[14] R. X. Fischer and E. Tillmanns, Acta Crystallogr. C44, 775 (1988).

[15] S. L. Mair, Acta Crystallogr. A 34, 542 (1978).[16] C. K. Johnson, ORTEP, A Fortran Thermal Elip-

soid Plot Program for Crystal Structure Illustra­tions, Oak Ridge National Laboratory, Oak Ridge, Tennessee (1971).

[17] R. S. Armstrong, J. K. Beattie, S. P. Best, B .W . Skelton, and A. H. White, J. Chem. Soc. Dalton Trans. 1983, 1973.

[18] R. S. Armstrong, J. K. Beattie, S. P. Best, G. P. Braithwaite, P. Del Favero, B. W. Skelton, and A. H. White, Aust. J. Chem. 43, 393 (1990).

[19] R. Caminiti and P. Cucca, Chem. Phys. Lett. 108, 51(1984).

[20] R. Caminiti, D . Atzei, P. Cucca, F. Squintu, and G. Bongiovanni, Z. Naturforsch. 40a, 1319 (1985).

[21] Y. Marcus, Chem. Rev. 88, 1475 (1988).[22] G. D. Fallon and L. Spiccia, Aust. J. Chem. 42,

2051 (1989).[23] F. Barcelo, P. Lahuerta, M. A. Ubeda, C. Foces-

Foces, F. H. Cano, and M. Martinez-Ripoll, J. Or­ganomet. Chem. 301, 375 (1986).

[24] M. Cano, J. V. Heras, M. A. Lobo, M. Martinez, E. Pinilla, E. Guttierrez, and M. A. Monge, Polyhe­dron 10, 187 (1991).

[25] I. D. Brown, in M. O’Keeffe and R. Navrotsky (eds): Structure and Bonding in Crystals, Vol. 2, Chapter 14, pp. Iff., Academie Press, New York(1981).

[26] E. Keller, SCHAKAL 88, A Fortran Program for the Graphical Representation of Molecular and Crystallographic Models, Universität Freiburg(1988).

[27] D. A. Buckingham and C. R. Clark, in G. Wilkin­son, R. D . Gillard, and J. A. Me Cleverty (eds): Comprehensive coordination Chemistry, Vol. 4, pp. 820ff., Pergamon, Oxford (1987).

[28] P. Colamarino and P. Orilio, J. Chem. Soc. Dalton Trans. 1976, 845.

[29] M. Calligaris, P. Faleschini and E. Alessio, Acta Crystallogr. C47, 747 (1991).

[30] A. F. Wells, Structural Inorganic Chemistry, 5th ed., pp. 81 ff., Clarendon, Oxford (1984).