Rubidium bis­(2-methyl­lactato)borate monohydrate

Gokila, G.; Thiruvalluvar, A.A.; Ramachandra Raja, C.

doi:10.1107/S2414314619000397

metal-organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 4| Part 1| January 2019| x190039

https://doi.org/10.1107/S2414314619000397

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Rubidium bis(2-methyllactato)borate monohydrate

Govindharajan Gokila,^a Aravazhi Amalan Thiruvalluvar ^b ^* and Chidambaram Ramachandra Raja ^a

^aDepartment of Physics, Government Arts College (Autonomous), Kumbakonam 612 002, Tamilnadu, India, and ^bPrincipal Kunthavai Naacchiyaar Government Arts College for Women (Autonomous), Thanjavur 613 007, Tamilnadu, India
^*Correspondence e-mail: thiruvalluvar.a@gmail.com

Edited by M. Weil, Vienna University of Technology, Austria (Received 27 December 2018; accepted 8 January 2019; online 15 January 2019)

The asymmetric unit of the inorganic–organic hybrid salt, poly[aqua[μ₄-bis(2-methyllactato)borato]rubidium], [Rb(C₈H₁₂BO₆)(H₂O)]_n, comprises a rubidium cation, a bis(2-methyllactato)borate anion, and a water molecule of crystallization. The rubidium cation is pseudo-octahedrally coordinated by five O atoms from four bis(2-methyllactato)borate ligands and by a water molecule. The presence of four coordinating O atoms within the anion lead to the formation of a polymeric three-dimensional framework structure that is consolidated by additional O—H⋯O hydrogen-bonding interactions.

Keywords: crystal structure; inorganic–organic hybrid material; borate.

CCDC reference: 1889484

Structure description

Alkaline cations such as lithium and potassium are used in the development of batteries. Allen et al. (2012 ) have reported the crystal structure of lithium bis(2-methyllactato)borate monohydrate. In our current study we have replaced the lithium cation by a rubidium cation and report here single-crystal growth and structural analysis of rubidium bis(2-methyllactato)borate monohydrate. Whereas the lithium salt crystallizes in the space group Pbca with Z = 8, the rubidium salt crystallizes in space group P2₁/n with Z = 4.

The asymmetric unit of the title compound comprises a rubidium cation, a bis(2-methyllactato)borate anion, and a water molecule of crystallization (Fig. 1). The structural features of the anion are very similar to that of the lithium salt (Allen et al., 2012), in particular with respect to B—O bond lengths (Table 1). The five-membered ring O1/C2/C1/O2/B1 adopts a half-chair conformation with a twist on the O1—C2 bond [puckering parameters Q₂ = 0.077 (3) Å, φ₂ = 198 (2)°] whereas the O4/C5/C6/O5/B1 ring adopts a slightly distorted half-chair conformation with a twist on the O5—B1 bond [puckering parameters Q₂ = 0.141 (3) Å, φ₂ = 303 (1)°]. The dihedral angle between the least-squares planes of the two five-membered rings is 89.30 (14)°. The rubidium cation is sixfold coordinated by one water molecule (O7) and five O atoms (O1, O6ⁱ, O6ⁱⁱ, O3ⁱⁱⁱ and O5; symmetry codes as in Table 1) from four bis(2-methyllactato)borate ligands, one of which coordinates in a bidentate mode (Table 1). The presence of four coordinating oxygen atoms per anion leads to the formation of a three-dimensional framework structure. Additional hydrogen bonds between the water molecules and one of the O atoms of the BO₄ tetrahedron (O5) and one of the carbonyl O atoms (O3) stabilizes the structural set-up (Fig. 2, Table 2).

Table 1
Selected bond lengths (Å)

Rb1—O7	2.833 (3)	Rb1—O3ⁱⁱⁱ	3.115 (2)
Rb1—O6ⁱ	2.8852 (19)	O1—B1	1.432 (3)
Rb1—O6ⁱⁱ	2.932 (2)	O2—B1	1.507 (3)
Rb1—O5	2.9766 (17)	O4—B1	1.506 (3)
Rb1—O1	3.0316 (18)	O5—B1	1.438 (3)
Symmetry codes: (i) x-1, y, z; (ii) -x+1, -y+2, -z+1; (iii) $[-x+{\script{1\over 2}}, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ .

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O7—H2⋯O5ⁱⁱⁱ	0.84 (2)	2.22 (2)	3.049 (3)	169 (5)
O7—H1⋯O3^iv	0.86 (4)	2.14 (4)	2.826 (4)	137 (4)
Symmetry codes: (iii) $[-x+{\script{1\over 2}}, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (iv) x, y+1, z.

Figure 1
The asymmetric unit of the title compound showing the atom numbering with displacement ellipsoids drawn at the 25% probability level.

Figure 2
Packing diagram of the title compound viewed along the a axis. Dashed lines indicate hydrogen bonds.

Synthesis and crystallization

The title compound was synthesized by reacting 2-methyllactic acid, boric acid and rubidium carbonate (molar ratio 4:2:1) in double distilled water. Slow evaporation of the solvent yielded good quality crystals within a period of 50 days.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3.

Table 3
Experimental details

Crystal data
Chemical formula	[Rb(C₈H₁₂BO₆)(H₂O)]
M_r	318.47
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	296
a, b, c (Å)	8.3075 (3), 10.4488 (4), 15.5630 (6)
β (°)	92.202 (2)
V (Å³)	1349.92 (9)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	3.69
Crystal size (mm)	0.15 × 0.10 × 0.10

Data collection
Diffractometer	Bruker Kappa APEX3 CMOS diffractometer
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.518, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	39188, 4927, 2964
R_int	0.062
(sin θ/λ)_max (Å⁻¹)	0.760

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.051, 0.105, 1.05
No. of reflections	4927
No. of parameters	160
No. of restraints	3
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.54, −0.80
Computer programs: APEX3 and SAINT (Bruker, 2016 ), SHELXT 2014/5 (Sheldrick, 2015a ), SHELXL2018/3 (Sheldrick, 2015b ), ORTEP-3 for Windows (Farrugia, 2012 ) and PLATON (Spek, 2009 ) and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 1889484

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314619000397/wm4095sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314619000397/wm4095Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314619000397/wm4095Isup3.cdx

Supporting information file. DOI: https://doi.org/10.1107/S2414314619000397/wm4095Isup4.cdx

checkCIF report

Computing details top

Data collection: APEX3 (Bruker, 2016); cell refinement: SAINT (Bruker, 2016); data reduction: SAINT (Bruker, 2016); program(s) used to solve structure: SHELXT 2014/5 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012), PLATON (Spek, 2009); software used to prepare material for publication: SHELXL2018/3 (Sheldrick, 2015b), PLATON (Spek, 2009) and publCIF (Westrip, 2010).

Poly[aqua[µ₄-bis(2-methyllactato)borato]rubidium] top

Crystal data top

[Rb(C₈H₁₂BO₆)(H₂O)]	F(000) = 640
M_r = 318.47	D_x = 1.567 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
a = 8.3075 (3) Å	Cell parameters from 9895 reflections
b = 10.4488 (4) Å	θ = 3.1–30.4°
c = 15.5630 (6) Å	µ = 3.69 mm⁻¹
β = 92.202 (2)°	T = 296 K
V = 1349.92 (9) Å³	Block, colourless
Z = 4	0.15 × 0.10 × 0.10 mm

Data collection top

Bruker Kappa APEX3 CMOS diffractometer	4927 independent reflections
Radiation source: fine-focus sealed tube	2964 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.062
ω and φ scan	θ_max = 32.7°, θ_min = 3.4°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −10→12
T_min = 0.518, T_max = 0.746	k = −15→15
39188 measured reflections	l = −23→23

Refinement top

Refinement on F²	3 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.051	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.105	w = 1/[σ²(F_o²) + (0.0378P)² + 0.7957P] where P = (F_o² + 2F_c²)/3
S = 1.05	(Δ/σ)_max = 0.002
4927 reflections	Δρ_max = 0.54 e Å⁻³
160 parameters	Δρ_min = −0.80 e Å⁻³

Special details top

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

Refinement. H atoms of the water molecule were discernable from difference Fourier maps and were refined with a distance constraint of d(O—H) = 0.85 (2) Å and U_iso(H) = 1.2U_eq(O).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Rb1	0.15594 (3)	1.03371 (3)	0.62254 (2)	0.04816 (10)
C1	0.3793 (3)	0.6083 (3)	0.64453 (16)	0.0424 (6)
C2	0.2674 (3)	0.6658 (3)	0.57496 (16)	0.0421 (6)
C3	0.2814 (5)	0.5932 (4)	0.4905 (2)	0.0764 (11)
H3A	0.241898	0.507568	0.497088	0.115*
H3B	0.218825	0.635964	0.445976	0.115*
H3C	0.392203	0.590459	0.475235	0.115*
C4	0.0954 (4)	0.6685 (4)	0.6045 (3)	0.0769 (11)
H4A	0.056836	0.582433	0.610491	0.115*
H4B	0.092286	0.711533	0.658929	0.115*
H4C	0.028243	0.713139	0.562860	0.115*
C5	0.7099 (3)	0.9182 (3)	0.59312 (15)	0.0379 (5)
C6	0.6303 (3)	0.9805 (3)	0.66890 (15)	0.0368 (5)
C7	0.6093 (4)	1.1224 (3)	0.6535 (2)	0.0615 (8)
H7A	0.713066	1.162725	0.653085	0.092*
H7B	0.553519	1.135858	0.599030	0.092*
H7C	0.547865	1.158700	0.698425	0.092*
C8	0.7251 (4)	0.9526 (4)	0.75202 (19)	0.0634 (9)
H8A	0.828318	0.993751	0.750896	0.095*
H8B	0.667126	0.984611	0.799709	0.095*
H8C	0.739760	0.861916	0.758072	0.095*
O1	0.32554 (19)	0.79284 (16)	0.56594 (11)	0.0390 (4)
O2	0.4970 (2)	0.68714 (18)	0.66442 (12)	0.0474 (5)
O3	0.3631 (3)	0.5045 (2)	0.67894 (15)	0.0624 (6)
O4	0.6196 (2)	0.82640 (19)	0.56029 (11)	0.0459 (4)
O5	0.47576 (18)	0.91984 (17)	0.66951 (10)	0.0372 (4)
O6	0.8396 (2)	0.9478 (2)	0.56534 (13)	0.0547 (5)
B1	0.4744 (3)	0.8096 (3)	0.61421 (17)	0.0365 (6)
O7	0.1465 (4)	1.2961 (3)	0.6680 (2)	0.0984 (10)
H1	0.221 (4)	1.340 (4)	0.645 (3)	0.118*
H2	0.108 (5)	1.339 (4)	0.708 (2)	0.118*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Rb1	0.03750 (14)	0.05453 (19)	0.05188 (16)	0.00398 (12)	−0.00565 (10)	−0.00967 (13)
C1	0.0420 (13)	0.0423 (16)	0.0427 (13)	−0.0021 (12)	−0.0025 (10)	0.0019 (12)
C2	0.0403 (13)	0.0405 (15)	0.0449 (13)	−0.0107 (11)	−0.0069 (10)	0.0040 (11)
C3	0.121 (3)	0.055 (2)	0.0518 (18)	−0.008 (2)	−0.0172 (19)	−0.0080 (16)
C4	0.0384 (16)	0.075 (3)	0.117 (3)	−0.0077 (16)	0.0017 (17)	0.034 (2)
C5	0.0289 (11)	0.0460 (15)	0.0384 (12)	−0.0019 (10)	−0.0009 (9)	0.0065 (11)
C6	0.0341 (11)	0.0423 (15)	0.0337 (11)	−0.0091 (11)	−0.0021 (9)	0.0000 (10)
C7	0.078 (2)	0.0421 (17)	0.0656 (18)	−0.0124 (16)	0.0160 (16)	−0.0013 (15)
C8	0.0521 (17)	0.096 (3)	0.0408 (14)	−0.0111 (17)	−0.0098 (12)	0.0050 (16)
O1	0.0356 (9)	0.0355 (10)	0.0450 (9)	−0.0057 (7)	−0.0100 (7)	0.0052 (7)
O2	0.0438 (10)	0.0402 (11)	0.0569 (11)	−0.0035 (8)	−0.0167 (8)	0.0063 (9)
O3	0.0730 (15)	0.0468 (12)	0.0664 (13)	−0.0106 (10)	−0.0102 (11)	0.0177 (10)
O4	0.0349 (9)	0.0563 (12)	0.0471 (9)	−0.0034 (8)	0.0086 (7)	−0.0139 (9)
O5	0.0292 (8)	0.0409 (10)	0.0418 (9)	−0.0081 (7)	0.0058 (7)	−0.0061 (7)
O6	0.0330 (9)	0.0748 (15)	0.0568 (11)	−0.0074 (9)	0.0094 (8)	0.0067 (10)
B1	0.0296 (12)	0.0405 (17)	0.0392 (14)	−0.0011 (11)	−0.0005 (10)	0.0008 (12)
O7	0.129 (3)	0.0592 (17)	0.111 (2)	−0.0272 (17)	0.0615 (19)	−0.0241 (16)

Geometric parameters (Å, º) top

Rb1—O7	2.833 (3)	C4—H4B	0.9600
Rb1—O6ⁱ	2.8852 (19)	C4—H4C	0.9600
Rb1—O6ⁱⁱ	2.932 (2)	C5—O6	1.216 (3)
Rb1—O5	2.9766 (17)	C5—O4	1.309 (3)
Rb1—O1	3.0316 (18)	C5—C6	1.521 (4)
Rb1—O3ⁱⁱⁱ	3.115 (2)	C6—O5	1.432 (3)
Rb1—B1	3.539 (3)	C6—C7	1.511 (4)
Rb1—C5ⁱⁱ	3.612 (2)	C6—C8	1.516 (4)
Rb1—C1ⁱⁱⁱ	3.730 (3)	C7—H7A	0.9600
Rb1—Rb1^iv	4.5823 (5)	C7—H7B	0.9600
Rb1—H1	3.27 (4)	C7—H7C	0.9600
C1—O3	1.219 (3)	C8—H8A	0.9600
C1—O2	1.307 (3)	C8—H8B	0.9600
C1—C2	1.523 (3)	C8—H8C	0.9600
C2—O1	1.421 (3)	O1—B1	1.432 (3)
C2—C4	1.518 (4)	O2—B1	1.507 (3)
C2—C3	1.526 (4)	O4—B1	1.506 (3)
C3—H3A	0.9600	O5—B1	1.438 (3)
C3—H3B	0.9600	O7—H1	0.857 (18)
C3—H3C	0.9600	O7—H2	0.844 (18)
C4—H4A	0.9600

O7—Rb1—O6ⁱ	110.16 (9)	O1—C2—C3	110.0 (2)
O7—Rb1—O6ⁱⁱ	100.75 (8)	C4—C2—C3	112.0 (3)
O6ⁱ—Rb1—O6ⁱⁱ	76.06 (6)	C1—C2—C3	110.6 (3)
O7—Rb1—O5	111.01 (9)	C2—C3—H3A	109.5
O6ⁱ—Rb1—O5	138.17 (6)	C2—C3—H3B	109.5
O6ⁱⁱ—Rb1—O5	103.06 (5)	H3A—C3—H3B	109.5
O7—Rb1—O1	153.31 (8)	C2—C3—H3C	109.5
O6ⁱ—Rb1—O1	94.58 (5)	H3A—C3—H3C	109.5
O6ⁱⁱ—Rb1—O1	75.01 (5)	H3B—C3—H3C	109.5
O5—Rb1—O1	47.09 (4)	C2—C4—H4A	109.5
O7—Rb1—O3ⁱⁱⁱ	81.04 (8)	C2—C4—H4B	109.5
O6ⁱ—Rb1—O3ⁱⁱⁱ	101.25 (6)	H4A—C4—H4B	109.5
O6ⁱⁱ—Rb1—O3ⁱⁱⁱ	177.14 (6)	C2—C4—H4C	109.5
O5—Rb1—O3ⁱⁱⁱ	78.24 (5)	H4A—C4—H4C	109.5
O1—Rb1—O3ⁱⁱⁱ	104.41 (5)	H4B—C4—H4C	109.5
O7—Rb1—B1	132.64 (9)	O6—C5—O4	123.3 (2)
O6ⁱ—Rb1—B1	117.12 (6)	O6—C5—C6	125.7 (2)
O6ⁱⁱ—Rb1—B1	88.23 (6)	O4—C5—C6	110.9 (2)
O5—Rb1—B1	23.52 (5)	O6—C5—Rb1ⁱⁱ	47.56 (13)
O1—Rb1—B1	23.60 (5)	O4—C5—Rb1ⁱⁱ	86.10 (13)
O3ⁱⁱⁱ—Rb1—B1	92.18 (6)	C6—C5—Rb1ⁱⁱ	145.07 (17)
O7—Rb1—C5ⁱⁱ	96.29 (8)	O5—C6—C7	109.7 (2)
O6ⁱ—Rb1—C5ⁱⁱ	93.82 (5)	O5—C6—C8	110.2 (2)
O6ⁱⁱ—Rb1—C5ⁱⁱ	17.83 (5)	C7—C6—C8	112.2 (2)
O5—Rb1—C5ⁱⁱ	88.82 (5)	O5—C6—C5	103.41 (19)
O1—Rb1—C5ⁱⁱ	71.47 (5)	C7—C6—C5	110.4 (2)
O3ⁱⁱⁱ—Rb1—C5ⁱⁱ	164.71 (6)	C8—C6—C5	110.6 (2)
B1—Rb1—C5ⁱⁱ	78.48 (6)	C6—C7—H7A	109.5
O7—Rb1—C1ⁱⁱⁱ	63.35 (8)	C6—C7—H7B	109.5
O6ⁱ—Rb1—C1ⁱⁱⁱ	105.08 (6)	H7A—C7—H7B	109.5
O6ⁱⁱ—Rb1—C1ⁱⁱⁱ	163.70 (6)	C6—C7—H7C	109.5
O5—Rb1—C1ⁱⁱⁱ	86.99 (5)	H7A—C7—H7C	109.5
O1—Rb1—C1ⁱⁱⁱ	120.69 (5)	H7B—C7—H7C	109.5
O3ⁱⁱⁱ—Rb1—C1ⁱⁱⁱ	17.75 (6)	C6—C8—H8A	109.5
B1—Rb1—C1ⁱⁱⁱ	105.10 (6)	C6—C8—H8B	109.5
C5ⁱⁱ—Rb1—C1ⁱⁱⁱ	155.85 (6)	H8A—C8—H8B	109.5
O7—Rb1—Rb1^iv	109.65 (8)	C6—C8—H8C	109.5
O6ⁱ—Rb1—Rb1^iv	38.39 (4)	H8A—C8—H8C	109.5
O6ⁱⁱ—Rb1—Rb1^iv	37.67 (4)	H8B—C8—H8C	109.5
O5—Rb1—Rb1^iv	127.87 (3)	C2—O1—B1	110.61 (19)
O1—Rb1—Rb1^iv	83.38 (3)	C2—O1—Rb1	125.67 (15)
O3ⁱⁱⁱ—Rb1—Rb1^iv	139.63 (5)	B1—O1—Rb1	98.49 (15)
B1—Rb1—Rb1^iv	105.50 (4)	C1—O2—B1	109.58 (19)
C5ⁱⁱ—Rb1—Rb1^iv	55.45 (4)	C1—O3—Rb1^v	111.07 (19)
C1ⁱⁱⁱ—Rb1—Rb1^iv	141.08 (4)	C5—O4—B1	109.10 (19)
O7—Rb1—H1	14.0 (5)	C6—O5—B1	109.72 (18)
O6ⁱ—Rb1—H1	118.9 (8)	C6—O5—Rb1	127.82 (14)
O6ⁱⁱ—Rb1—H1	92.0 (7)	B1—O5—Rb1	100.76 (13)
O5—Rb1—H1	103.0 (8)	C5—O6—Rb1^vi	141.11 (17)
O1—Rb1—H1	140.3 (6)	C5—O6—Rb1ⁱⁱ	114.61 (16)
O3ⁱⁱⁱ—Rb1—H1	90.2 (7)	Rb1^vi—O6—Rb1ⁱⁱ	103.94 (6)
B1—Rb1—H1	122.2 (7)	O1—B1—O5	113.5 (2)
C5ⁱⁱ—Rb1—H1	84.8 (6)	O1—B1—O4	114.6 (2)
C1ⁱⁱⁱ—Rb1—H1	73.1 (6)	O5—B1—O4	104.6 (2)
Rb1^iv—Rb1—H1	109.0 (8)	O1—B1—O2	104.9 (2)
O3—C1—O2	123.4 (2)	O5—B1—O2	111.8 (2)
O3—C1—C2	126.1 (2)	O4—B1—O2	107.5 (2)
O2—C1—C2	110.5 (2)	O1—B1—Rb1	57.91 (12)
O3—C1—Rb1^v	51.18 (15)	O5—B1—Rb1	55.72 (12)
O2—C1—Rb1^v	89.28 (14)	O4—B1—Rb1	123.99 (16)
C2—C1—Rb1^v	134.79 (17)	O2—B1—Rb1	128.41 (16)
O1—C2—C4	109.9 (2)	Rb1—O7—H1	113 (3)
O1—C2—C1	103.79 (19)	Rb1—O7—H2	135 (3)
C4—C2—C1	110.3 (2)	H1—O7—H2	109 (3)

O3—C1—C2—O1	172.0 (3)	C8—C6—O5—B1	−105.2 (3)
O2—C1—C2—O1	−7.0 (3)	C5—C6—O5—B1	13.0 (2)
Rb1^v—C1—C2—O1	103.7 (2)	C7—C6—O5—Rb1	8.8 (3)
O3—C1—C2—C4	54.3 (4)	C8—C6—O5—Rb1	132.8 (2)
O2—C1—C2—C4	−124.6 (3)	C5—C6—O5—Rb1	−108.92 (18)
Rb1^v—C1—C2—C4	−14.0 (4)	O4—C5—O6—Rb1^vi	−143.6 (2)
O3—C1—C2—C3	−70.1 (4)	C6—C5—O6—Rb1^vi	36.5 (4)
O2—C1—C2—C3	110.9 (3)	Rb1ⁱⁱ—C5—O6—Rb1^vi	171.8 (4)
Rb1^v—C1—C2—C3	−138.4 (2)	O4—C5—O6—Rb1ⁱⁱ	44.6 (3)
O6—C5—C6—O5	174.6 (2)	C6—C5—O6—Rb1ⁱⁱ	−135.3 (2)
O4—C5—C6—O5	−5.3 (3)	C2—O1—B1—O5	−129.3 (2)
Rb1ⁱⁱ—C5—C6—O5	109.6 (3)	Rb1—O1—B1—O5	4.0 (2)
O6—C5—C6—C7	57.3 (3)	C2—O1—B1—O4	110.6 (2)
O4—C5—C6—C7	−122.6 (3)	Rb1—O1—B1—O4	−116.0 (2)
Rb1ⁱⁱ—C5—C6—C7	−7.7 (4)	C2—O1—B1—O2	−7.0 (3)
O6—C5—C6—C8	−67.4 (3)	Rb1—O1—B1—O2	126.33 (16)
O4—C5—C6—C8	112.7 (2)	C2—O1—B1—Rb1	−133.32 (19)
Rb1ⁱⁱ—C5—C6—C8	−132.5 (2)	C6—O5—B1—O1	−141.1 (2)
C4—C2—O1—B1	126.4 (3)	Rb1—O5—B1—O1	−4.1 (2)
C1—C2—O1—B1	8.4 (3)	C6—O5—B1—O4	−15.5 (2)
C3—C2—O1—B1	−109.9 (3)	Rb1—O5—B1—O4	121.45 (15)
C4—C2—O1—Rb1	8.8 (3)	C6—O5—B1—O2	100.5 (2)
C1—C2—O1—Rb1	−109.23 (18)	Rb1—O5—B1—O2	−122.48 (16)
C3—C2—O1—Rb1	132.4 (2)	C6—O5—B1—Rb1	−136.98 (18)
O3—C1—O2—B1	−176.1 (3)	C5—O4—B1—O1	137.0 (2)
C2—C1—O2—B1	2.8 (3)	C5—O4—B1—O5	12.1 (3)
Rb1^v—C1—O2—B1	−135.54 (17)	C5—O4—B1—O2	−106.9 (2)
O2—C1—O3—Rb1^v	56.6 (3)	C5—O4—B1—Rb1	70.3 (2)
C2—C1—O3—Rb1^v	−122.2 (2)	C1—O2—B1—O1	2.4 (3)
O6—C5—O4—B1	175.9 (2)	C1—O2—B1—O5	125.8 (2)
C6—C5—O4—B1	−4.2 (3)	C1—O2—B1—O4	−120.0 (2)
Rb1ⁱⁱ—C5—O4—B1	−152.81 (16)	C1—O2—B1—Rb1	63.0 (3)
C7—C6—O5—B1	130.8 (2)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O7—H2···O5ⁱⁱⁱ	0.84 (2)	2.22 (2)	3.049 (3)	169 (5)
O7—H1···O3^vii	0.86 (4)	2.14 (4)	2.826 (4)	137 (4)

Symmetry codes: (iii) −x+1/2, y+1/2, −z+3/2; (vii) x, y+1, z.

Acknowledgements

The authors thank the Sophisticated Analytical Instrument Facility (SAIF), Indian Institute of Technology Madras (IITM), Chennai 600 036, Tamilnadu, India, for recording the single-crystal X-ray diffraction data.

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