The mixed-valent titanium phosphate, Li(2)Ti(2)(PO(4))(3), dilithium dititanium(III/IV) tris-(orthophosphate).

The mixed-valent titanium phosphate, Li(2)Ti(2)(PO(4))(3), has been prepared by the reactive halide flux method. The title compound is isostructural with Li(2)TiM(PO(4))(3) (M = Fe, Cr) and Li(2)FeZr(PO(4))(3) and has the same (3) (∞)[Ti(2)(PO(4))(3)](2-) framework as the previously reported Li(3-) (x)M(2)(PO(4))(3) phases. The framework is built up from corner-sharing TiO(6) octa-hedra and PO(4) tetra-hedra, one of which has 2 symmetry. The Li(+) ions are located on one crystallographic position and reside in the vacancies of the framework. They are surrounded by four O atoms in a distorted tetra-hedral coordination. The classical charge-balance of the title compound can be represented as Li(+) (2)(Ti(3+)/Ti(4+))(PO(4) (3-))(3).

Related literature

The synthesis and structural characterization of stoichiometric Li2TiM(PO4)3 (M = Fe and Cr) and Li2FeZr(PO4)3 have been reported by Patoux et al. (2004 ▶) and Catti (2001 ▶), respectively. For related phosphates with general formula Li3- 2(PO4)3 (0 ≤ x ≤ 1), see: Wang & Hwu (1991 ▶) for Li2.72Ti2(PO4)3. For Li batteries based on Li3- 2(PO4)3 phases, see: Yin et al. (2003 ▶). For ionic conductivities of these phases, see: Sato et al. (2000 ▶). For ionic radii, see: Shannon (1976 ▶). For structure validation, see: Spek (2009 ▶).

Experimental

Crystal data

Li2Ti2(PO4)3

M = 394.59

Orthorhombic,

a = 12.0344 (5) Å

b = 8.5795 (5) Å

c = 8.6794 (4) Å

V = 896.14 (7) Å3

Z = 4

Mo Kα radiation

μ = 2.39 mm−1

T = 290 K

0.22 × 0.16 × 0.14 mm

Data collection

Rigaku R-AXIS RAPID diffractometer

Absorption correction: multi-scan (ABSCOR; Higashi, 1995 ▶) T min = 0.802, T max = 1.000

6671 measured reflections

1004 independent reflections

974 reflections with I > 2σ(I)

R int = 0.035

Refinement

R[F 2 > 2σ(F 2)] = 0.046

wR(F 2) = 0.112

S = 1.37

1004 reflections

87 parameters

Δρmax = 0.49 e Å−3

Δρmin = −0.74 e Å−3

Data collection: RAPID-AUTO (Rigaku, 2006 ▶); cell refinement: RAPID-AUTO; data reduction: RAPID-AUTO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: locally modified version of ORTEP (Johnson, 1965 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536811031606/wm2513sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811031606/wm2513Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Li2Ti2(PO4)3	F(000) = 764
Mr = 394.59	Dx = 2.925 Mg m−3
Orthorhombic, Pbcn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2n 2ab	Cell parameters from 6390 reflections
a = 12.0344 (5) Å	θ = 3.3–27.4°
b = 8.5795 (5) Å	µ = 2.39 mm−1
c = 8.6794 (4) Å	T = 290 K
V = 896.14 (7) Å3	Block, black
Z = 4	0.22 × 0.16 × 0.14 mm

Rigaku R-AXIS RAPID diffractometer	1004 independent reflections
Radiation source: sealed tube	974 reflections with I > 2σ(I)
Graphite	Rint = 0.035
ω scans	θmax = 27.4°, θmin = 3.4°
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	h = −14→14
Tmin = 0.802, Tmax = 1.000	k = −11→11
6671 measured reflections	l = −11→11

Refinement on F2	87 parameters
Least-squares matrix: full	0 restraints
R[F2 > 2σ(F2)] = 0.046	w = 1/[σ2(Fo2) + (0.P)2 + 10.7789P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.112	(Δ/σ)max < 0.001
S = 1.37	Δρmax = 0.49 e Å−3
1004 reflections	Δρmin = −0.74 e Å−3

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.

	x	y	z	Uiso*/Ueq
Li	0.1812 (9)	0.2861 (13)	0.2191 (12)	0.020 (2)
Ti	0.38824 (7)	0.25295 (11)	0.03788 (11)	0.0077 (2)
P1	0.5	0.5399 (2)	0.25	0.0086 (4)
P2	0.35246 (11)	0.10469 (15)	0.39437 (15)	0.0069 (3)
O1	0.4200 (3)	0.3537 (5)	−0.1627 (5)	0.0186 (9)
O2	0.4304 (4)	0.4408 (5)	0.1413 (5)	0.0219 (10)
O3	0.5306 (4)	0.1556 (5)	0.0618 (5)	0.0217 (10)
O4	0.2282 (3)	0.3271 (5)	0.0130 (4)	0.0152 (8)
O5	0.3221 (3)	0.1629 (5)	0.2322 (4)	0.0137 (8)
O6	0.3443 (3)	0.0729 (4)	−0.1040 (5)	0.0146 (8)

	U11	U22	U33	U12	U13	U23
Li	0.019 (5)	0.025 (5)	0.017 (5)	0.002 (4)	0.005 (4)	−0.004 (4)
Ti	0.0076 (4)	0.0079 (4)	0.0078 (4)	0.0006 (3)	0.0001 (3)	−0.0007 (4)
P1	0.0114 (9)	0.0075 (8)	0.0071 (8)	0	0.0023 (7)	0
P2	0.0060 (6)	0.0079 (6)	0.0067 (6)	0.0001 (5)	−0.0003 (5)	−0.0001 (5)
O1	0.018 (2)	0.025 (2)	0.0126 (18)	−0.0112 (17)	0.0036 (17)	−0.0017 (17)
O2	0.031 (3)	0.018 (2)	0.016 (2)	−0.0095 (18)	−0.0074 (19)	0.0006 (17)
O3	0.021 (2)	0.019 (2)	0.025 (2)	0.0074 (17)	−0.0096 (19)	−0.0075 (18)
O4	0.017 (2)	0.020 (2)	0.0087 (17)	0.0098 (16)	−0.0012 (16)	0.0001 (15)
O5	0.0107 (18)	0.021 (2)	0.0096 (17)	0.0007 (15)	0.0008 (16)	0.0035 (16)
O6	0.0131 (19)	0.0084 (18)	0.022 (2)	−0.0007 (14)	−0.0049 (17)	0.0013 (16)

Li—O4	1.909 (11)	P1—O2iv	1.521 (4)
Li—O6i	1.979 (11)	P1—O1v	1.528 (4)
Li—O1i	1.994 (12)	P1—O1vi	1.528 (4)
Li—O5	2.001 (11)	P1—Livii	3.048 (11)
Li—Tii	2.909 (10)	P1—Liviii	3.048 (11)
Li—Ti	2.960 (10)	P2—O3iv	1.522 (4)
Li—P2	2.997 (11)	P2—O6ix	1.527 (4)
Li—P2ii	2.998 (11)	P2—O4i	1.531 (4)
Li—P1iii	3.048 (11)	P2—O5	1.537 (4)
Ti—O2	1.913 (4)	P2—Lii	2.998 (11)
Ti—O3	1.917 (4)	O1—P1vi	1.528 (4)
Ti—O1	1.981 (4)	O1—Liii	1.994 (12)
Ti—O5	2.019 (4)	O3—P2iv	1.522 (4)
Ti—O4	2.039 (4)	O4—P2ii	1.531 (4)
Ti—O6	2.045 (4)	O6—P2x	1.527 (4)
Ti—Liii	2.909 (10)	O6—Liii	1.979 (11)
P1—O2	1.521 (4)
O4—Li—O6i	131.3 (6)	O2—P1—O1vi	111.9 (2)
O4—Li—O1i	140.7 (6)	O2iv—P1—O1vi	107.1 (2)
O6i—Li—O1i	82.7 (4)	O1v—P1—O1vi	106.6 (4)
O4—Li—O5	84.2 (4)	O3iv—P2—O6ix	110.1 (2)
O6i—Li—O5	114.2 (5)	O3iv—P2—O4i	108.0 (2)
O1i—Li—O5	99.8 (5)	O6ix—P2—O4i	109.5 (2)
O2—Ti—O3	94.55 (19)	O3iv—P2—O5	110.8 (2)
O2—Ti—O1	89.61 (18)	O6ix—P2—O5	108.5 (2)
O3—Ti—O1	96.49 (19)	O4i—P2—O5	109.9 (2)
O2—Ti—O5	92.03 (18)	P1vi—O1—Ti	144.9 (3)
O3—Ti—O5	95.45 (18)	P1vi—O1—Liii	119.3 (4)
O1—Ti—O5	167.79 (17)	Ti—O1—Liii	94.1 (3)
O2—Ti—O4	92.14 (19)	P1—O2—Ti	155.2 (3)
O3—Ti—O4	172.33 (19)	P2iv—O3—Ti	168.1 (3)
O1—Ti—O4	87.31 (17)	P2ii—O4—Li	120.8 (4)
O5—Ti—O4	80.54 (16)	P2ii—O4—Ti	142.1 (2)
O2—Ti—O6	170.86 (18)	Li—O4—Ti	97.1 (4)
O3—Ti—O6	88.11 (17)	P2—O5—Li	115.2 (4)
O1—Ti—O6	81.39 (17)	P2—O5—Ti	142.7 (2)
O5—Ti—O6	96.43 (16)	Li—O5—Ti	94.8 (4)
O4—Ti—O6	85.86 (16)	P2x—O6—Liii	127.8 (4)
O2—P1—O2iv	112.1 (3)	P2x—O6—Ti	138.0 (3)
O2—P1—O1v	107.1 (2)	Liii—O6—Ti	92.6 (4)
O2iv—P1—O1v	111.9 (2)