Poly[diaquadi-μ₆-oxalato-μ₅-oxalato-chromium(III)rubidium(I)]: a new supra­molecular isomer

The title compound, [CrRb(C₂O₄)₂(H₂O)₂]_n, obtained under hydro­thermal conditions and investigated structurally at 100 K, is a three-dimensional supra­molecular isomer of the layered structure compound studied at room temperature. This novel polymer is built up from crosslinked hetero­bimetallic units. The linkage of alternating edge- and vertex-shared RbO₇(H₂O)₂ and CrO₄(H₂O)₂ polyhedra running along three different directions gives a dense packing. The two independent ligands display two η⁴-chelation modes and two conventional carboxyl­ate bridges. However, the penta­dentate ligand connects the Cr^III and Rb^I ions through one O-atom bridge, while the hexa­dentate ligand exhibits an additional η³-chelation and two O-atom bridges. Each coordinated water mol­ecule forms an O-atom bridge between the two metals. Moreover, in the absence of protonated ligands, these water mol­ecules act as donors through their four H atoms in strong-to-weak hydrogen bonds. This results in zigzag chains of alternating oxalate and aqua ligands parallel to the twofold screw axis. The six double oxalates known to date containing an alkali and Cr^III all present layered two-dimensional structures. In the series, this supra­molecular isomer is the first three-dimensional framework.

S1. Comment

In recent years, the design of new supramolecular architectures using dicarboxylic acids as linkers has received great attention (Rao et al., 2004), opening a wide research field for the generation of coordination polymers with various dimensionalities (Janiak, 2003; Cheetham et al., 2006). Built up from discrete binuclear entities, chains, layers or three-dimensional crosslinked polynuclear units, these polymers create various kind of voids, leading to solids also called metal–organic frameworks (MOFs; Tranchemontagne et al., 2009). Their open structures exhibit porosity which can be successfully used in ion exchange and gas storage (Czaja et al., 2009; Uemura et al., 2009; Yaghi & Li, 1996; Robinson & Zaworotko, 1995; Hoskins & Robson, 1990; Murray et al., 2009). In the resulting extended network, some intrinsic structural features govern the tuneability and functionality of these materials. Among them, metal–oxalate based compounds occupy a particular place, due to the variety of behaviours introduced by this simplest dicarboxylic acid. Therefore, the properties they can display range from controlled complex thermal decomposition for the development of metal oxide nanoparticles (Audebrand et al., 2003) to induced electronic interactions, via their rich bridging coordination modes for the formation of magnetic and multiferroic crystals (Coronado et al., 1996; Mosaad et al., 1995; Price et al., 2003; Zhang et al., 2008; Schaack, 1990). Concerning the connectors, in reticular chemistry the use of two metals to obtain a specific heterometallic framework from individual components in solution remains a challenge in the areas of both crystal engineering and crystal structure (Wang & Cohen, 2009). In this context, and as part of our research concerning polymeric dicarboxylates (Aliouane et al., 2007; Djehni et al., 2007; Rahahlia et al., 2007), we have selected alkali and transition metals. By providing several kinds of non-covalent interactions, including metal coordination, hydrogen bonding and ionic characteristics, they may extend the scope of potential applications. We report in this paper the structure of the title new diaqua bis(µ-oxalato)chromium(III)rubidium(I) complex, [CrRb(C₂O₄)₂(H₂O)₂]_n, which is a supramolecular isomer of the rubidium chromium dioxalate dihydrate previously studied at room temperature (Kolitsch, 2004).

The structure of [CrRb(C₂O₄)₂(H₂O)₂]_n is a three-dimensional MOF. The asymmetric unit corresponds to the chemical formula (see table of crystal data). The structure is made up of RbO₇(H₂O)₂ and CrO₄(H₂O)₂ edge-sharing polyhedra through the two aqua ligands, without any solvent water. Although they are crystallographically independent, the two oxalate ligands are surrounded by the same number of metal ions - three different Rb^I atoms and one Cr^III - and present a rather usual anti–anti conformation (Table 1). They are approximately planar within experimental error; the largest deviations from the mean planes formed by the ligands L1 (atoms O1/O2/C1/C2/O3/O4) and L2 (O5/O6/C3/C4/O7/O8) are 0.0348 (11) and 0.1183 (11) Å, respectively, [For which atoms?]. They are nearly perpendicular to each other, the dihedral angle being 88.02 (5)°. However, ligand L2 is pentadentate, displaying two conventional µ-1,3 carboxylate bridges and an η⁴-chelate so-called malonate mode, forming a five-membered ring (Cr/O5/O3/C4/O7). Moreover, one end functional group is involved in a µ-oxo bridge through atom O5 and links together one Rb^I ion and one Cr^III ion. Like L2, ligand L1 exhibits two conventional carboxylate bridges and one η⁴ malonate mode formed by atoms Cr/O4/C2/C1/O2. However, it is hexadentate, due to the two triply ligating atoms O4 and O2, which are involved in one µ-oxo bridge. Thus, this ligand is simultaneously η⁴-chelating through its carbon backbone and η³-chelating, with the alkali Rb^I ion, through one functional group (O1/C1/O2). To the best of our knowledge, this latter kind of chelate is very rare for alkali metals. Therefore, it can be reasonably assumed that the mainly electrostatic bonding commonly encountered with alkali cations is, in this case, behind the coordination character of the Rb—O linkage.

As seen in Fig. 1 and Table 1, the first coordination sphere of the Rb^I ion is consists of five O atoms from three L2, one L1 and two aqua ligands. In the second coordination sphere, two contacts >3.10 Å are provided by two [O?] atoms, both belonging to one L1 ligand. In this nona-coordination, the central atom is involved in one four-membered nonplanar ring (Rb/O1/C1/O2), in which the largest deviation from the mean plane is 0.1336 (8) Å [For which atom?]. This leads to a notably short distance between the Rb^I ion and atom C1 [3.3176 (17) Å]. The next longest Rb—O contact is 3.717 (4) Å, which we consider too long to be significant. This steric constraint is probably responsible for the wide range of Rb—O bond lengths [2.8790 (12)–3.3371 (13) Å] and angles [42.82 (3)–158.67 (3)°]. However, the Rb—O distances are close to the expected values for homo- or heterometallic oxalate-based compounds (Dinnebier et al., 2003; Kolitsch, 2004).

On the basis of the first coordination sphere, the resulting coordination polyhedron is a slightly distorted trigonal antiprism exhibiting two planes approximately parallel to each other [the dihedral angle between the sets of atoms O2W/O2ⁱⁱⁱ/O1W and O4ⁱⁱ/O1ⁱⁱⁱ/O5^iv is 7.58 (6)°; all symmetry codes as in Table 1?] and an axial cap (O3ⁱ). Taking into account the second coordination sphere, the nona-coordination gives an environment which cannot be described in term of a regular dodecahedron, although the dihedral angle between the two trapezoids formed by the sets of atoms O1W/O8^vi/O1ⁱⁱⁱ/O6^v [maximum deviation 0.0358 (6) Å For which atom?] and O4ⁱⁱ/O3ⁱ/O2W/O2ⁱⁱⁱ [maximum deviation 0.3724 (6) Å For which atom?] is 74.53 (2)°, which is near to the ideal value for a dodecahedron having D₂ symmetry (Drew, 1977; Marrot & Trombe, 1993). In this case, atom O5^iv constitutes the cap, even though its distance from the metal atom is not the largest. However, we note that the Rb^I ion is offset and does not lie in the plane of the trapezoids, and that one deviation is too large. As can be seen at the top of Fig. 2, this polyhedron is highly distorted compared with the hepta-coordination environment given by the first coordination sphere.

Regarding the CrO₄(H₂O)₂ octahedron, it is very slightly distorted, with two longer Cr—O bonds to aqua ligands, and with bond angles which are not exactly 90° as a regular octahedral arrangement would imply. This can be explained by the small bite angles of the chelates within each oxalate ligand [82.42 (5) and 82.52 (5)°]. However, the coordination geometries around the metal centre are not distorted. Indeed, unlike RbO₇(H₂O)₂, around Cr^III the two rings are almost planar; the largest deviations from the mean planes are 0.0217 (9) and 0.0524 (9) Å [For which atoms?] for the five-membered cycles subtended by ligands L1 and L2, respectively. Moreover, the smaller ranges of bond lengths [1.9524 (12)–1.9918 (13) Å] and angles [82.42 (5)–96.47 (5)°] are comparable with other oxalates having the same connectivity (Ballester et al., 2001; Kolitsch, 2004; Kahlenberg et al., 2008). In the octahedral environment formed around the metal centre, the smaller deviation from the mean plane [0.0300 (7) Å For which atom?] is given by a plane which is nearly in the same plane as the η⁴-chelate provided by ligand L2 and it contains four atoms in equatorial positions (O2W/O2/O5/O7), including one water molecule. The other aqua ligand occupies the axial position with atom O4 of one η⁴-chelate (L1). The Cr^III environment indicates significant local symmetry: the chosen equatorial plane and the η⁴-chelate provided by L2 are nearly in the same plane, the dihedral angle between them being 2.22 (4)°, highlighting the particular arrangement of the two oxalate ligands towards this equatorial plane.

The overall three-dimensional framework, viewed along the b axis (Fig. 3), shows the small empty channels running along helicoidal axis, surrounded by Cr^III and Rb^I polyhedra, and hydrogen-bonded oxalate and aqua ligands. The Rb^I dodecahedra and Cr^III octahedra show three common vertices belonging to three different oxalate ligands, and one common edge formed by the two aqua ligands. This results in the formation of three different chains of alternating edge-shared and vertex-shared polyhedra. As depicted at the bottom of Fig. 2 and in Fig. 3, these chains run in a zigzag fashion along the c axis via an O5 bridge, and along the b axis via an O2 bridge. Another chain, in which the shortest Rb—Cr distance is observed [4.1192 (3) Å], runs approximately in the a-axis direction. Projections of the bipolyhedral chains in the (001) and (100) planes are shown in Fig. 4. In this structure, unlike the homometallic ones studied previously (Kherfi et al., 2010), the two ligands are completely deprotonated, which rules out the building of supramolecular R_a^d synthons (Bernstein et al., 1995). The hydrogen-bonding pattern is due only to water molecules, which act as donors to the O atoms which are not included in the η⁴-chelation. The corresponding bonds are strong and nearly linear, forming infinite helicoidal chains (Table 2). However, the unique atom O5, which belongs to one five-membered ring, is involved in a weak bond and in a bifurcated hydrogen bond.

A comparison of the title structure with the structurally studied oxalates containing alkali and alkaline earth or transition metals reveals the singular three-dimensional framework of this material. Indeed, the complexes [KCr(C₂O₄)₂(H₂O)₂].3H₂O (van Niekerk & Schoening, 1951), [A₃Cr(C₂O₄)₃].yH₂O, with A = K or Rb and y = unknown or 3 (van Niekerk & Schoening, 1952a,b; Merrachi et al., 1987), [ACr(C₂O₄)₂].2H₂O, with A = Rb or NH₄ (Kolitsch, 2004; Kahlenberg et al., 2008) and [A₂M^II(C₂O₄)₂].xH₂O, with A = K, Rb or Cs and M = Co, Mg or Cu (Viswamitra, 1962; Weichert & Lohn, 1974; Gleizes et al., 1980; Kolitsch, 2004), are all two-dimensional layered structures with the metal ions lying in special positions. Although they belong essentially to monoclinic centrosymmetric space groups (C2/m, P2/c, P2₁/c and C2/c, [Respectively?]), they display several differing features. In particular, the two isotypic compounds [RbCr(C₂O₄)₂].2H₂O (Kolitsch, 2004), studied at room temperature, and (NH₄)[Cr(C₂O₄)₂].2H₂O (Kahlenberg et al., 2008), studied at 173 K and at room temperature, elegantly display a close relationship on a microscopic level and show that, from both chemical and structural points of view, the NH₄⁺ cation resembles an s-block element. However, it presents two disordered orientations, which can be explained by its different role in the structure. It is a counterion lying in between the layers to accomplish charge balance, while in the title complex the Rb^I ion is included in the building blocks. In the corresponding structure studied at room temperature (Kolitsch, 2004), instead of the structure presented here, the water molecules are not bonded to the Rb^I ion but only to the Cr^III ion, and in two apical trans positions. Therefore, the two resulting metal coordination polyhedra, RbO₈ and CrO₄(H₂O), have no common edge and the structure consists of alternating layers of Cr^III and Rb^I polyhedra connected via the unique ligand. Within the layers, adjacent Cr^III octahedra are linked via hydrogen bonds and adjacent Rb^I tetragonal prisms form infinite Rb—O—Rb—O chains, as in some typical MOFs. In the present compound, the heterobimetallic Rb—O—Cr—O units are connected into infinite arrays through oxo-bridges and without similar infinite chains. However, the structure can be affiliated to MOFs owing to its secondary building unit and its empty voids (Tranchemontagne et al., 2009).

From a structural point of view, the compound presented here, studied at 100 K, can be considered as a supramolecular isomer (Robin & Fromm, 2006) of the compound having the same chemical formula and studied at room temperature in space group C2/m (Kolitsch, 2004). The novel structural arrangement observed here, highlighting interpenetrated layers, might be the consequence of the hydrothermal synthesis conditions, which result in a higher dimensionality with small channels.

Related literature

For related literature, see: Aliouane et al. (2007); Audebrand et al. (2003); Ballester et al. (2001); Bernstein et al. (1995); Cheetham et al. (2006); Coronado et al. (1996); Czaja et al. (2009); Dinnebier et al. (2003); Djehni et al. (2007); Drew (1977); Gleizes et al. (1980); Hoskins & Robson (1990); Janiak (2003); Kahlenberg et al. (2008); Kherfi et al. (2010); Kolitsch (2004); Marrot & Trombe (1993); Merrachi et al. (1987); Mosaad et al. (1995); Murray et al. (2009); Niekerk & Schoening (1951, 1952a); Price et al. (2003); Rahahlia et al. (2007); Rao et al. (2004); Robin & Fromm (2006); Robinson & Zaworotko (1995); Schaack (1990); Tranchemontagne et al. (2009); Uemura et al. (2009); Viswamitra (1962); Wang & Cohen (2009); Weichert & Lohn (1974); Yaghi & Li (1996); Zhang et al. (2008).

S2. Experimental

A mixture of rubidium carbonate (0.173 g, 0.75 mmol), chromium nitrate nonahydrate (0.200 g, 0.5 mmol) and oxalic acid dihydrate (0.189 g, 1.5 mmol) in deionized water (15 ml) was introduced into a 23 ml Teflon-lined stainless steel vessel. The vessel was sealed and heated at 393 K for one week. Dark-pink single crystals of suitable size were obtained after cooling the vessel to room temperature. They were filtered off and washed with diethyl ether.

S3. Refinement

Water H atoms were located in a difference Fourier map and refined with a restrained O—H distance of 0.85 (5) Å. The highest electron density in the final difference Fourier map is 0.77 Å from atom C1 and the deepest hole is 0.39 Å from the Cr^III ion.

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2009); cell refinement: CrysAlis RED (Oxford Diffraction, 2009); data reduction: CrysAlis RED (Oxford Diffraction, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. A segment of the polymeric structure, showing the environment around the metal atoms and the bridging positions of the water molecules. Displacement ellipsoids are drawn at the 50% probability level. (Symmetry codes are as in Table 1.)
	Fig. 2. Top: the coordination polyhedra around the Rb atom, taking into account the two coordination spheres (left) or only the first coordination sphere (right). Bottom: a perspective view (ligand L2 removed), showing chains running along the b and a axes. [Please provide what were illegible labels and check those that have been added]
	Fig. 3. A packing diagram, viewed along [010], showing the empty channels.
	Fig. 4. Projections of the bipolyhedra in the (001) and (100) planes.

Poly[diaquadi-µ₆-oxalato-µ₅-oxalato-chromium(III)rubidium(I)]

Crystal data

[CrRb(C2O4)2(H2O)2]	F(000) = 676
Mr = 349.54	Dx = 2.567 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 170 reflections
a = 6.8506 (1) Å	θ = 3.2–39.2°
b = 10.521 (1) Å	µ = 6.66 mm^−1
c = 12.6995 (2) Å	T = 100 K
β = 98.773 (2)°	Prismatic, pink
V = 904.61 (9) Å^3	0.3 × 0.2 × 0.2 mm
Z = 4

Data collection

Oxford Xcalibur diffractometer	1938 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.033
Graphite monochromator	θmax = 28.0°, θmin = 3.2°
ω scans	h = −9→9
Absorption correction: numerical [CrysAlis RED (Oxford Diffraction, 2009), based on expressions derived by Clark & Reid (1995)]	k = −13→13
Tmin = 0.221, Tmax = 0.264	l = −16→16
18885 measured reflections	3 standard reflections every 100 reflections
2178 independent reflections	intensity decay: 0.01%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.016	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.044	All H-atom parameters refined
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0276P)^2 + 0.0505P] where P = (Fo^2 + 2Fc^2)/3
2178 reflections	(Δ/σ)max = 0.012
161 parameters	Δρmax = 0.44 e Å^−3
6 restraints	Δρmin = −0.46 e Å^−3

Special details

Experimental. CrysAlis RED (Oxford Diffraction, 2009). Analytical numerical absorption correction using a multifaceted crystal model based on expressions derived by Clark & Reid (1995).

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Rb1	0.88724 (2)	0.151716 (15)	0.812464 (13)	0.01235 (6)
Cr1	0.35730 (4)	0.25216 (2)	0.63297 (2)	0.00663 (7)
C1	0.1966 (3)	0.49353 (16)	0.61044 (13)	0.0093 (3)
C2	0.0332 (2)	0.40559 (16)	0.64104 (13)	0.0098 (3)
C3	0.2224 (2)	0.07790 (15)	0.47576 (13)	0.0089 (3)
C4	0.3039 (2)	0.00028 (16)	0.57657 (14)	0.0092 (3)
O1	0.17158 (19)	0.60743 (11)	0.59530 (10)	0.0134 (3)
O2	0.35891 (17)	0.43429 (11)	0.60363 (9)	0.0104 (2)
O3	−0.13498 (17)	0.44563 (12)	0.64382 (10)	0.0137 (3)
O4	0.08936 (17)	0.28984 (11)	0.66034 (10)	0.0102 (2)
O5	0.25040 (18)	0.19877 (11)	0.48716 (9)	0.0096 (2)
O6	0.13881 (18)	0.02585 (11)	0.39465 (9)	0.0127 (3)
O7	0.34615 (17)	0.06910 (11)	0.66076 (9)	0.0102 (2)
O8	0.32660 (18)	−0.11484 (11)	0.57248 (10)	0.0128 (3)
O1W	0.63306 (18)	0.24070 (12)	0.60184 (10)	0.0109 (3)
H1	0.662 (4)	0.202 (2)	0.5536 (18)	0.042 (8)*
H2	0.689 (4)	0.3061 (18)	0.607 (2)	0.034 (7)*
O2W	0.47570 (19)	0.27580 (12)	0.78405 (10)	0.0100 (2)
H3	0.515 (3)	0.3410 (15)	0.8111 (17)	0.015 (6)*
H4	0.442 (3)	0.2290 (18)	0.8249 (16)	0.019 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Rb1	0.01021 (9)	0.01096 (9)	0.01633 (9)	0.00228 (6)	0.00344 (6)	0.00318 (6)
Cr1	0.00591 (13)	0.00565 (12)	0.00803 (13)	−0.00007 (10)	0.00008 (10)	−0.00058 (10)
C1	0.0095 (8)	0.0102 (7)	0.0077 (8)	−0.0003 (6)	−0.0004 (6)	−0.0011 (6)
C2	0.0091 (8)	0.0111 (8)	0.0083 (8)	−0.0007 (7)	−0.0012 (6)	−0.0036 (6)
C3	0.0068 (7)	0.0102 (7)	0.0101 (8)	0.0018 (6)	0.0022 (6)	0.0004 (6)
C4	0.0062 (8)	0.0103 (7)	0.0113 (8)	−0.0006 (6)	0.0016 (6)	0.0016 (6)
O1	0.0179 (6)	0.0086 (5)	0.0140 (6)	0.0022 (5)	0.0037 (5)	0.0004 (5)
O2	0.0086 (6)	0.0074 (5)	0.0154 (6)	0.0003 (5)	0.0022 (5)	0.0000 (5)
O3	0.0075 (6)	0.0141 (6)	0.0190 (7)	0.0016 (5)	0.0007 (5)	−0.0048 (5)
O4	0.0080 (6)	0.0085 (5)	0.0140 (6)	−0.0003 (5)	0.0016 (5)	−0.0005 (5)
O5	0.0110 (6)	0.0074 (5)	0.0097 (6)	−0.0005 (5)	−0.0007 (5)	0.0001 (5)
O6	0.0163 (6)	0.0102 (6)	0.0102 (6)	0.0006 (5)	−0.0029 (5)	−0.0009 (5)
O7	0.0118 (6)	0.0080 (5)	0.0100 (6)	−0.0006 (5)	−0.0008 (5)	−0.0008 (5)
O8	0.0185 (7)	0.0078 (5)	0.0122 (6)	0.0004 (5)	0.0022 (5)	−0.0005 (5)
O1W	0.0090 (6)	0.0096 (6)	0.0146 (6)	−0.0016 (5)	0.0031 (5)	−0.0043 (5)
O2W	0.0117 (6)	0.0091 (6)	0.0088 (6)	−0.0036 (5)	0.0001 (5)	−0.0004 (5)

Geometric parameters (Å, º)

Rb1—O3^i	2.8790 (12)	Cr1—O1W	1.9918 (13)
Rb1—O4^ii	2.9287 (12)	C1—O1	1.222 (2)
Rb1—O2^iii	2.9711 (12)	C1—O2	1.289 (2)
Rb1—O5^iv	2.9849 (12)	C2—O3	1.232 (2)
Rb1—O2W	3.0778 (13)	C2—O4	1.289 (2)
Rb1—O1W	3.1053 (13)	C3—O6	1.228 (2)
Rb1—O1^iii	3.1054 (13)	C3—O5	1.291 (2)
Rb1—O6^v	3.2089 (12)	C4—O8	1.223 (2)
Rb1—C1^iii	3.3176 (17)	C4—O7	1.287 (2)
Rb1—O8^vi	3.3371 (13)	C1—C2	1.547 (2)
Cr1—O2	1.9524 (12)	C3—C4	1.549 (2)
Cr1—O4	1.9600 (12)	O1W—H1	0.79 (2)
Cr1—O7	1.9615 (12)	O1W—H2	0.79 (2)
Cr1—O5	1.9665 (12)	O2W—H3	0.796 (18)
Cr1—O2W	1.9814 (13)	O2W—H4	0.78 (2)
O3^i—Rb1—O4^ii	149.20 (3)	O6^v—Rb1—H3	114.1 (3)
O3^i—Rb1—O2^iii	71.74 (3)	C1^iii—Rb1—H3	162.2 (4)
O4^ii—Rb1—O2^iii	107.99 (3)	O8^vi—Rb1—H3	87.7 (3)
O3^i—Rb1—O5^iv	89.30 (3)	C2^ii—Rb1—H3	80.5 (4)
O4^ii—Rb1—O5^iv	117.55 (3)	Cr1—Rb1—H3	37.9 (3)
O2^iii—Rb1—O5^iv	111.85 (3)	H2—Rb1—H3	56.4 (6)
O3^i—Rb1—O2W	77.06 (3)	O3^i—Rb1—H4	64.8 (3)
O4^ii—Rb1—O2W	103.24 (3)	O4^ii—Rb1—H4	117.3 (3)
O2^iii—Rb1—O2W	147.59 (3)	O2^iii—Rb1—H4	133.8 (3)
O5^iv—Rb1—O2W	58.51 (3)	O5^iv—Rb1—H4	54.3 (4)
O3^i—Rb1—O1W	96.83 (3)	O2W—Rb1—H4	14.1 (3)
O4^ii—Rb1—O1W	62.72 (3)	O1W—Rb1—H4	63.3 (3)
O2^iii—Rb1—O1W	139.61 (3)	O1^iii—Rb1—H4	154.7 (4)
O5^iv—Rb1—O1W	106.44 (3)	O6^v—Rb1—H4	104.8 (4)
O2W—Rb1—O1W	52.25 (3)	C1^iii—Rb1—H4	154.2 (3)
O3^i—Rb1—O1^iii	113.11 (3)	O8^vi—Rb1—H4	107.1 (4)
O4^ii—Rb1—O1^iii	78.02 (3)	C2^ii—Rb1—H4	101.1 (3)
O2^iii—Rb1—O1^iii	42.82 (3)	Cr1—Rb1—H4	36.1 (4)
O5^iv—Rb1—O1^iii	101.34 (3)	H2—Rb1—H4	67.6 (6)
O2W—Rb1—O1^iii	158.32 (3)	H3—Rb1—H4	23.4 (5)
O1W—Rb1—O1^iii	139.09 (3)	O2—Cr1—O4	82.42 (5)
O3^i—Rb1—O6^v	76.09 (3)	O2—Cr1—O7	178.08 (5)
O4^ii—Rb1—O6^v	73.80 (3)	O4—Cr1—O7	95.94 (5)
O2^iii—Rb1—O6^v	78.58 (3)	O2—Cr1—O5	96.47 (5)
O5^iv—Rb1—O6^v	158.67 (3)	O4—Cr1—O5	90.02 (5)
O2W—Rb1—O6^v	102.44 (3)	O7—Cr1—O5	82.52 (5)
O1W—Rb1—O6^v	61.03 (3)	O2—Cr1—O2W	92.76 (5)
O1^iii—Rb1—O6^v	98.69 (3)	O4—Cr1—O2W	93.38 (5)
O3^i—Rb1—C1^iii	94.56 (4)	O7—Cr1—O2W	88.31 (5)
O4^ii—Rb1—C1^iii	88.40 (4)	O5—Cr1—O2W	170.51 (5)
O2^iii—Rb1—C1^iii	22.81 (4)	O2—Cr1—O1W	89.33 (5)
O5^iv—Rb1—C1^iii	113.47 (4)	O4—Cr1—O1W	171.74 (5)
O2W—Rb1—C1^iii	167.97 (4)	O7—Cr1—O1W	92.32 (5)
O1W—Rb1—C1^iii	138.52 (4)	O5—Cr1—O1W	91.38 (5)
O1^iii—Rb1—C1^iii	21.60 (4)	O2W—Cr1—O1W	86.52 (5)
O6^v—Rb1—C1^iii	83.55 (4)	O2—Cr1—Rb1	109.10 (4)
O3^i—Rb1—O8^vi	143.10 (3)	O4—Cr1—Rb1	136.38 (4)
O4^ii—Rb1—O8^vi	67.57 (3)	O7—Cr1—Rb1	72.77 (3)
O2^iii—Rb1—O8^vi	97.88 (3)	O5—Cr1—Rb1	128.17 (4)
O5^iv—Rb1—O8^vi	61.11 (3)	O2W—Cr1—Rb1	45.60 (4)
O2W—Rb1—O8^vi	101.86 (3)	O1W—Cr1—Rb1	46.51 (4)
O1W—Rb1—O8^vi	111.72 (3)	O1—C1—O2	124.42 (16)
O1^iii—Rb1—O8^vi	58.15 (3)	O1—C1—C2	122.48 (16)
O6^v—Rb1—O8^vi	137.98 (3)	O2—C1—C2	113.11 (14)
C1^iii—Rb1—O8^vi	79.57 (4)	O1—C1—Rb1^vi	69.38 (10)
O3^i—Rb1—C2^ii	152.39 (4)	O2—C1—Rb1^vi	63.32 (9)
O4^ii—Rb1—C2^ii	18.38 (3)	C2—C1—Rb1^vi	148.02 (10)
O2^iii—Rb1—C2^ii	125.04 (3)	O3—C2—O4	124.81 (16)
O5^iv—Rb1—C2^ii	101.63 (3)	O3—C2—C1	121.22 (15)
O2W—Rb1—C2^ii	87.10 (4)	O4—C2—C1	113.96 (14)
O1W—Rb1—C2^ii	55.86 (3)	O3—C2—Rb1^vii	83.78 (10)
O1^iii—Rb1—C2^ii	89.74 (3)	O4—C2—Rb1^vii	45.74 (8)
O6^v—Rb1—C2^ii	85.63 (3)	C1—C2—Rb1^vii	148.78 (11)
C1^iii—Rb1—C2^ii	103.89 (4)	O6—C3—O5	125.14 (15)
O8^vi—Rb1—C2^ii	61.98 (3)	O6—C3—C4	121.41 (15)
O3^i—Rb1—Cr1	78.21 (2)	O5—C3—C4	113.45 (14)
O4^ii—Rb1—Cr1	88.46 (2)	O8—C4—O7	125.34 (16)
O2^iii—Rb1—Cr1	144.51 (2)	O8—C4—C3	121.27 (15)
O5^iv—Rb1—Cr1	85.75 (2)	O7—C4—C3	113.38 (14)
O2W—Rb1—Cr1	27.38 (2)	C1—O1—Rb1^vi	89.02 (11)
O1W—Rb1—Cr1	27.73 (2)	C1—O2—Cr1	115.57 (11)
O1^iii—Rb1—Cr1	166.44 (2)	C1—O2—Rb1^vi	93.87 (9)
O6^v—Rb1—Cr1	76.21 (2)	Cr1—O2—Rb1^vi	135.01 (5)
C1^iii—Rb1—Cr1	159.59 (3)	C2—O3—Rb1^viii	148.69 (11)
O8^vi—Rb1—Cr1	117.57 (2)	C2—O4—Cr1	114.70 (11)
C2^ii—Rb1—Cr1	77.43 (3)	C2—O4—Rb1^vii	115.88 (10)
O3^i—Rb1—H2	110.3 (3)	Cr1—O4—Rb1^vii	124.50 (5)
O4^ii—Rb1—H2	52.7 (4)	C3—O5—Cr1	114.50 (10)
O2^iii—Rb1—H2	146.8 (5)	C3—O5—Rb1^ix	119.60 (10)
O5^iv—Rb1—H2	101.3 (4)	Cr1—O5—Rb1^ix	115.80 (5)
O2W—Rb1—H2	54.6 (5)	C3—O6—Rb1^v	155.16 (11)
O1W—Rb1—H2	14.2 (3)	C4—O7—Cr1	114.38 (10)
O1^iii—Rb1—H2	130.7 (4)	C4—O8—Rb1^iii	141.27 (11)
O6^v—Rb1—H2	70.3 (4)	Cr1—O1W—Rb1	105.75 (5)
C1^iii—Rb1—H2	137.3 (5)	Cr1—O1W—H1	123 (2)
O8^vi—Rb1—H2	97.6 (3)	Rb1—O1W—H1	110 (2)
C2^ii—Rb1—H2	42.9 (3)	Cr1—O1W—H2	113.3 (19)
Cr1—Rb1—H2	35.8 (4)	Rb1—O1W—H2	89 (2)
O3^i—Rb1—H3	88.2 (3)	H1—O1W—H2	110 (3)
O4^ii—Rb1—H3	98.2 (4)	Cr1—O2W—Rb1	107.02 (5)
O2^iii—Rb1—H3	153.4 (4)	Cr1—O2W—H3	126.0 (16)
O5^iv—Rb1—H3	48.9 (4)	Rb1—O2W—H3	94.1 (16)
O2W—Rb1—H3	14.2 (3)	Cr1—O2W—H4	116.6 (18)
O1W—Rb1—H3	58.1 (4)	Rb1—O2W—H4	90.8 (17)
O1^iii—Rb1—H3	144.7 (3)	H3—O2W—H4	112 (2)
O3^i—Rb1—Cr1—O2	159.05 (5)	C2—C1—O2—Rb1^vi	−144.85 (11)
O4^ii—Rb1—Cr1—O2	−48.89 (4)	O4—Cr1—O2—C1	−2.27 (11)
O2^iii—Rb1—Cr1—O2	−168.53 (5)	O5—Cr1—O2—C1	86.89 (11)
O5^iv—Rb1—Cr1—O2	68.88 (4)	O2W—Cr1—O2—C1	−95.32 (12)
O2W—Rb1—Cr1—O2	74.47 (6)	O1W—Cr1—O2—C1	178.20 (12)
O1W—Rb1—Cr1—O2	−69.79 (6)	Rb1—Cr1—O2—C1	−138.88 (10)
O1^iii—Rb1—Cr1—O2	−53.32 (11)	O4—Cr1—O2—Rb1^vi	123.50 (8)
O6^v—Rb1—Cr1—O2	−122.58 (4)	O5—Cr1—O2—Rb1^vi	−147.35 (7)
C1^iii—Rb1—Cr1—O2	−130.13 (9)	O2W—Cr1—O2—Rb1^vi	30.45 (8)
O8^vi—Rb1—Cr1—O2	14.70 (5)	O1W—Cr1—O2—Rb1^vi	−56.03 (8)
C2^ii—Rb1—Cr1—O2	−34.05 (4)	Rb1—Cr1—O2—Rb1^vi	−13.12 (8)
O3^i—Rb1—Cr1—O4	59.79 (6)	O4—C2—O3—Rb1^viii	146.93 (15)
O4^ii—Rb1—Cr1—O4	−148.15 (7)	C1—C2—O3—Rb1^viii	−34.5 (3)
O2^iii—Rb1—Cr1—O4	92.21 (6)	Rb1^vii—C2—O3—Rb1^viii	125.49 (19)
O5^iv—Rb1—Cr1—O4	−30.38 (6)	O3—C2—O4—Cr1	173.16 (13)
O2W—Rb1—Cr1—O4	−24.79 (7)	C1—C2—O4—Cr1	−5.47 (17)
O1W—Rb1—Cr1—O4	−169.05 (7)	Rb1^vii—C2—O4—Cr1	−156.36 (13)
O1^iii—Rb1—Cr1—O4	−152.58 (11)	O3—C2—O4—Rb1^vii	−30.5 (2)
O6^v—Rb1—Cr1—O4	138.16 (6)	C1—C2—O4—Rb1^vii	150.89 (10)
C1^iii—Rb1—Cr1—O4	130.61 (10)	O2—Cr1—O4—C2	4.44 (11)
O8^vi—Rb1—Cr1—O4	−84.56 (6)	O7—Cr1—O4—C2	−174.57 (11)
C2^ii—Rb1—Cr1—O4	−133.31 (6)	O5—Cr1—O4—C2	−92.09 (11)
O3^i—Rb1—Cr1—O7	−20.51 (4)	O2W—Cr1—O4—C2	96.78 (11)
O4^ii—Rb1—Cr1—O7	131.54 (4)	Rb1—Cr1—O4—C2	114.24 (10)
O2^iii—Rb1—Cr1—O7	11.91 (5)	O2—Cr1—O4—Rb1^vii	−149.60 (7)
O5^iv—Rb1—Cr1—O7	−110.69 (4)	O7—Cr1—O4—Rb1^vii	31.39 (7)
O2W—Rb1—Cr1—O7	−105.10 (6)	O5—Cr1—O4—Rb1^vii	113.88 (6)
O1W—Rb1—Cr1—O7	110.64 (6)	O2W—Cr1—O4—Rb1^vii	−57.26 (7)
O1^iii—Rb1—Cr1—O7	127.12 (10)	Rb1—Cr1—O4—Rb1^vii	−39.79 (8)
O6^v—Rb1—Cr1—O7	57.85 (4)	O6—C3—O5—Cr1	172.24 (13)
C1^iii—Rb1—Cr1—O7	50.31 (9)	C4—C3—O5—Cr1	−7.25 (17)
O8^vi—Rb1—Cr1—O7	−164.86 (4)	O6—C3—O5—Rb1^ix	−43.8 (2)
C2^ii—Rb1—Cr1—O7	146.38 (4)	C4—C3—O5—Rb1^ix	136.74 (10)
O3^i—Rb1—Cr1—O5	−85.86 (5)	O2—Cr1—O5—C3	−178.16 (11)
O4^ii—Rb1—Cr1—O5	66.20 (5)	O4—Cr1—O5—C3	−95.79 (12)
O2^iii—Rb1—Cr1—O5	−53.44 (6)	O7—Cr1—O5—C3	0.20 (11)
O5^iv—Rb1—Cr1—O5	−176.03 (4)	O1W—Cr1—O5—C3	92.36 (11)
O2W—Rb1—Cr1—O5	−170.45 (7)	Rb1—Cr1—O5—C3	61.31 (12)
O1W—Rb1—Cr1—O5	45.29 (7)	O2—Cr1—O5—Rb1^ix	36.44 (6)
O1^iii—Rb1—Cr1—O5	61.77 (11)	O4—Cr1—O5—Rb1^ix	118.81 (5)
O6^v—Rb1—Cr1—O5	−7.49 (5)	O7—Cr1—O5—Rb1^ix	−145.21 (6)
C1^iii—Rb1—Cr1—O5	−15.04 (10)	O1W—Cr1—O5—Rb1^ix	−53.05 (6)
O8^vi—Rb1—Cr1—O5	129.79 (5)	Rb1—Cr1—O5—Rb1^ix	−84.10 (5)
C2^ii—Rb1—Cr1—O5	81.04 (5)	O5—C3—O6—Rb1^v	112.6 (2)
O3^i—Rb1—Cr1—O2W	84.58 (6)	C4—C3—O6—Rb1^v	−68.0 (3)
O4^ii—Rb1—Cr1—O2W	−123.36 (6)	O8—C4—O7—Cr1	164.82 (14)
O2^iii—Rb1—Cr1—O2W	117.00 (6)	C3—C4—O7—Cr1	−14.02 (16)
O5^iv—Rb1—Cr1—O2W	−5.59 (6)	O4—Cr1—O7—C4	97.65 (11)
O1W—Rb1—Cr1—O2W	−144.26 (7)	O5—Cr1—O7—C4	8.41 (11)
O1^iii—Rb1—Cr1—O2W	−127.79 (11)	O2W—Cr1—O7—C4	−169.12 (11)
O6^v—Rb1—Cr1—O2W	162.95 (6)	O1W—Cr1—O7—C4	−82.68 (11)
C1^iii—Rb1—Cr1—O2W	155.40 (10)	Rb1—Cr1—O7—C4	−125.48 (11)
O8^vi—Rb1—Cr1—O2W	−59.76 (6)	O7—C4—O8—Rb1^iii	−29.7 (3)
C2^ii—Rb1—Cr1—O2W	−108.52 (6)	C3—C4—O8—Rb1^iii	149.05 (12)
O3^i—Rb1—Cr1—O1W	−131.16 (6)	O2—Cr1—O1W—Rb1	117.52 (5)
O4^ii—Rb1—Cr1—O1W	20.90 (5)	O7—Cr1—O1W—Rb1	−63.45 (5)
O2^iii—Rb1—Cr1—O1W	−98.73 (6)	O5—Cr1—O1W—Rb1	−146.02 (5)
O5^iv—Rb1—Cr1—O1W	138.67 (6)	O2W—Cr1—O1W—Rb1	24.71 (5)
O2W—Rb1—Cr1—O1W	144.26 (7)	O3^i—Rb1—O1W—Cr1	47.93 (5)
O1^iii—Rb1—Cr1—O1W	16.47 (11)	O4^ii—Rb1—O1W—Cr1	−156.34 (6)
O6^v—Rb1—Cr1—O1W	−52.79 (5)	O2^iii—Rb1—O1W—Cr1	117.67 (5)
C1^iii—Rb1—Cr1—O1W	−60.33 (10)	O5^iv—Rb1—O1W—Cr1	−43.36 (5)
O8^vi—Rb1—Cr1—O1W	84.50 (6)	O2W—Rb1—O1W—Cr1	−19.86 (4)
C2^ii—Rb1—Cr1—O1W	35.74 (6)	O1^iii—Rb1—O1W—Cr1	−174.17 (4)
O1—C1—C2—O3	5.4 (3)	O6^v—Rb1—O1W—Cr1	117.87 (6)
O2—C1—C2—O3	−175.04 (15)	C1^iii—Rb1—O1W—Cr1	152.77 (5)
Rb1^vi—C1—C2—O3	108.7 (2)	O8^vi—Rb1—O1W—Cr1	−108.23 (5)
O1—C1—C2—O4	−175.92 (16)	C2^ii—Rb1—O1W—Cr1	−136.46 (6)
O2—C1—C2—O4	3.6 (2)	O2—Cr1—O2W—Rb1	−114.29 (5)
Rb1^vi—C1—C2—O4	−72.6 (2)	O4—Cr1—O2W—Rb1	163.15 (5)
O1—C1—C2—Rb1^vii	−133.68 (18)	O7—Cr1—O2W—Rb1	67.30 (5)
O2—C1—C2—Rb1^vii	45.9 (3)	O1W—Cr1—O2W—Rb1	−25.12 (5)
Rb1^vi—C1—C2—Rb1^vii	−30.3 (3)	O3^i—Rb1—O2W—Cr1	−89.30 (5)
O6—C3—C4—O8	15.9 (2)	O4^ii—Rb1—O2W—Cr1	59.06 (6)
O5—C3—C4—O8	−164.59 (16)	O2^iii—Rb1—O2W—Cr1	−105.19 (7)
O6—C3—C4—O7	−165.22 (15)	O5^iv—Rb1—O2W—Cr1	173.46 (7)
O5—C3—C4—O7	14.3 (2)	O1W—Rb1—O2W—Cr1	20.11 (4)
O2—C1—O1—Rb1^vi	−32.92 (17)	O1^iii—Rb1—O2W—Cr1	149.89 (7)
C2—C1—O1—Rb1^vi	146.59 (14)	O6^v—Rb1—O2W—Cr1	−16.95 (6)
O1—C1—O2—Cr1	179.60 (14)	C1^iii—Rb1—O2W—Cr1	−135.86 (17)
C2—C1—O2—Cr1	0.05 (17)	O8^vi—Rb1—O2W—Cr1	128.50 (5)
Rb1^vi—C1—O2—Cr1	144.90 (9)	C2^ii—Rb1—O2W—Cr1	67.92 (5)
O1—C1—O2—Rb1^vi	34.70 (18)

Symmetry codes: (i) −x+1/2, y−1/2, −z+3/2; (ii) x+1, y, z; (iii) −x+3/2, y−1/2, −z+3/2; (iv) x+1/2, −y+1/2, z+1/2; (v) −x+1, −y, −z+1; (vi) −x+3/2, y+1/2, −z+3/2; (vii) x−1, y, z; (viii) −x+1/2, y+1/2, −z+3/2; (ix) x−1/2, −y+1/2, z−1/2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1···O8^v	0.79 (2)	1.86 (2)	2.6301 (18)	167
O1W—H2···O3^ii	0.79 (2)	1.91 (2)	2.6832 (18)	167
O2W—H3···O6^iv	0.80 (2)	1.88 (2)	2.6641 (17)	169
O2W—H3···O5^iv	0.80 (2)	2.58 (2)	2.9641 (17)	111
O2W—H4···O1^i	0.78 (2)	1.87 (2)	2.6410 (18)	171

Symmetry codes: (i) −x+1/2, y−1/2, −z+3/2; (ii) x+1, y, z; (iv) x+1/2, −y+1/2, z+1/2; (v) −x+1, −y, −z+1.