The crystal structure of cesbronite, Cu₃TeO₄(OH)₄: a novel sheet tellurate topology

The crystal structure of cesbronite has been determined using single-crystal X-ray diffraction and supported by electron-microprobe analysis, powder diffraction and Raman spectroscopy. Cesbronite is orthorhombic, space group Cmcm, with a = 2.93172 (16), b = 11.8414 (6), c = 8.6047 (4) Å and V = 298.72 (3) ų. The chemical formula of cesbronite has been revised to Cu^II₃Te^VIO₄(OH)₄ from Cu^II₅(Te^IVO₃)₂(OH)₆·2H₂O. This change has been accepted by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association, Proposal 17-C. The previously reported oxidation state of tellurium has been shown to be incorrect; the crystal structure, bond valence studies and charge balance clearly show tellurium to be hexavalent. The crystal structure of cesbronite is formed from corrugated sheets of edge-sharing CuO₆ and (Cu_0.5Te_0.5)O₆ octahedra. The structure determined here is an average structure that has underlying ordering of Cu and Te at one of the two metal sites, designated as M, which has an occupancy Cu_0.5Te_0.5. This averaging probably arises from an absence of correlation between adjacent polyhedral sheets, as there are two different hydrogen-bonding configurations linking sheets that are related by a ½a offset. Randomised stacking of these two configurations results in the superposition of Cu and Te and leads to the Cu_0.5Te_0.5 occupancy of the M site in the average structure. Bond-valence analysis is used to choose the most probable Cu/Te ordering scheme and also to identify protonation sites (OH). The chosen ordering scheme and its associated OH sites are shown to be consistent with the revised chemical formula.

Computing details

Data collection: CrysAlis PRO, Agilent Technologies, Version 1.171.35.19 (release 27-10-2011 CrysAlis171 .NET); cell refinement: CrysAlis PRO, Agilent Technologies, Version 1.171.35.19 (release 27-10-2011 CrysAlis171 .NET); data reduction: CrysAlis PRO, Agilent Technologies, Version 1.171.35.19 (release 27-10-2011 CrysAlis171 .NET); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2016/6 (Sheldrick, 2016).

(I)

Crystal data

Cu3O8TeH4	Dx = 4.961 Mg m^−3
Mr = 446.22	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Cmcm	Cell parameters from 857 reflections
a = 2.93172 (16) Å	θ = 5.9–31.1°
b = 11.8414 (6) Å	µ = 15.37 mm^−1
c = 8.6047 (4) Å	T = 293 K
V = 298.72 (3) Å^3	Triangular plate, translucent emerald green
Z = 2	0.05 × 0.03 × 0.02 mm
F(000) = 406

Data collection

Xcalibur, Eos diffractometer	763 independent reflections
Radiation source: Enhance (Mo) X-ray Source	649 reflections with I > 2σ(I)
Detector resolution: 16.0869 pixels mm^-1	Rint = 0.037
1K CCD area detector scans	θmax = 32.7°, θmin = 3.4°
Absorption correction: multi-scan Multi-scan ABSPACK	h = −4→4
Tmin = 0.801, Tmax = 1.000	k = −17→17
764 measured reflections	l = −12→12

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	H-atom parameters not defined
R[F^2 > 2σ(F^2)] = 0.032	w = 1/[σ^2(Fo^2) + (0.0378P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.068	(Δ/σ)max < 0.001
S = 1.04	Δρmax = 1.45 e Å^−3
326 reflections	Δρmin = −2.09 e Å^−3
25 parameters

Special details

Experimental. CrysAlisPro, Agilent Technologies, Version 1.171.36.28 (release 01-02-2013 CrysAlis171 .NET) (compiled Feb 1 2013,16:14:44) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.

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. Refined as a 2-component twin.

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cu1	0.000000	0.35007 (10)	0.750000	0.0076 (3)
Te2	−0.500000	0.500000	0.500000	0.0061 (2)	0.509 (9)
Cu2	−0.500000	0.500000	0.500000	0.0061 (2)	0.491 (9)
O1	−0.500000	0.4614 (7)	0.750000	0.038 (2)
O2	−0.500000	0.2384 (5)	0.750000	0.0086 (12)
O3	−1.000000	0.3928 (4)	0.4789 (4)	0.0087 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0051 (5)	0.0085 (6)	0.0092 (5)	0.000	0.000	0.000
Te2	0.0039 (3)	0.0078 (4)	0.0066 (3)	0.000	0.000	0.0005 (3)
Cu2	0.0039 (3)	0.0078 (4)	0.0066 (3)	0.000	0.000	0.0005 (3)
O1	0.008 (3)	0.008 (3)	0.097 (8)	0.000	0.000	0.000
O2	0.005 (3)	0.009 (3)	0.011 (3)	0.000	0.000	0.000
O3	0.0097 (19)	0.008 (2)	0.008 (2)	0.000	0.000	0.0002 (16)

Geometric parameters (Å, º)

Cu1—O1^i	1.971 (5)	Te2—O3^iv	1.948 (3)
Cu1—O1	1.971 (5)	Te2—O3^v	1.948 (3)
Cu1—O2^i	1.974 (4)	Te2—O3^i	1.948 (3)
Cu1—O2	1.974 (4)	Te2—O3	1.948 (3)
Cu1—O3^ii	2.387 (4)	Te2—O1	2.1992 (17)
Cu1—O3^i	2.387 (4)	Te2—O1^iv	2.1992 (17)
Cu1—Cu1^i	2.9317 (2)	Te2—Te2^iii	2.9317 (1)
Cu1—Cu1^iii	2.9317 (2)	Te2—Te2^i	2.9317 (2)
O1^i—Cu1—O1	96.1 (3)	O3^i—Te2—O3	97.64 (19)
O1^i—Cu1—O2^i	84.0 (2)	O3^iv—Te2—O1	92.53 (17)
O1—Cu1—O2^i	179.9 (2)	O3^v—Te2—O1	92.53 (17)
O1^i—Cu1—O2	179.9 (2)	O3^i—Te2—O1	87.47 (17)
O1—Cu1—O2	84.0 (2)	O3—Te2—O1	87.47 (17)
O2^i—Cu1—O2	95.9 (3)	O3^iv—Te2—O1^iv	87.47 (17)
O1^i—Cu1—O3^ii	81.85 (7)	O3^v—Te2—O1^iv	87.47 (17)
O1—Cu1—O3^ii	81.85 (7)	O3^i—Te2—O1^iv	92.53 (17)
O2^i—Cu1—O3^ii	98.16 (7)	O3—Te2—O1^iv	92.53 (17)
O2—Cu1—O3^ii	98.16 (7)	O1—Te2—O1^iv	180.0
O1^i—Cu1—O3^i	81.85 (7)	O3^iv—Te2—Te2^iii	138.82 (10)
O1—Cu1—O3^i	81.85 (7)	O3^v—Te2—Te2^iii	41.18 (10)
O2^i—Cu1—O3^i	98.16 (7)	O3^i—Te2—Te2^iii	138.82 (10)
O2—Cu1—O3^i	98.16 (7)	O3—Te2—Te2^iii	41.18 (10)
O3^ii—Cu1—O3^i	155.5 (2)	O1—Te2—Te2^iii	90.000 (1)
O1^i—Cu1—Cu1^i	41.97 (17)	O1^iv—Te2—Te2^iii	90.000 (1)
O1—Cu1—Cu1^i	138.03 (17)	O3^iv—Te2—Te2^i	41.18 (10)
O2^i—Cu1—Cu1^i	42.05 (13)	O3^v—Te2—Te2^i	138.82 (10)
O2—Cu1—Cu1^i	137.95 (13)	O3^i—Te2—Te2^i	41.18 (10)
O3^ii—Cu1—Cu1^i	90.0	O3—Te2—Te2^i	138.82 (10)
O3^i—Cu1—Cu1^i	90.0	O1—Te2—Te2^i	90.000 (1)
O1^i—Cu1—Cu1^iii	138.03 (17)	O1^iv—Te2—Te2^i	90.000 (1)
O1—Cu1—Cu1^iii	41.97 (17)	Te2^iii—Te2—Te2^i	180.0
O2^i—Cu1—Cu1^iii	137.95 (13)	Cu1^iii—O1—Cu1	96.1 (3)
O2—Cu1—Cu1^iii	42.05 (13)	Cu1^iii—O1—Te2^vi	97.99 (11)
O3^ii—Cu1—Cu1^iii	90.0	Cu1—O1—Te2^vi	97.99 (11)
O3^i—Cu1—Cu1^iii	90.000 (1)	Cu1^iii—O1—Te2	97.99 (11)
Cu1^i—Cu1—Cu1^iii	180.0	Cu1—O1—Te2	97.99 (11)
O3^iv—Te2—O3^v	97.64 (19)	Te2^vi—O1—Te2	156.0 (4)
O3^iv—Te2—O3^i	82.36 (19)	Cu1—O2—Cu1^iii	95.9 (3)
O3^v—Te2—O3^i	180.0	Te2—O3—Te2^iii	97.63 (19)
O3^iv—Te2—O3	180.0	Te2—O3—Cu1^iii	92.69 (13)
O3^v—Te2—O3	82.36 (19)	Te2^iii—O3—Cu1^iii	92.69 (13)

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