Sr3MgPtO6

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Acta Cryst.(2003). E59, i75±i76 DOI: 10.1107/S1600536803005993 Smith and zur Loye Sr₃MgPtO₆

i75

inorganic papers

Acta Crystallographica Section E

Structure Reports Online

ISSN 1600-5368

Sr

3

MgPtO

6

Mark D. Smith and Hans-Conrad zur Loye*

Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA

Correspondence e-mail: [email protected]

Key indicators

Single-crystal X-ray study

T= 293 K

Mean(Mg±O) = 0.004 AÊ

Rfactor = 0.024

wRfactor = 0.049

Data-to-parameter ratio = 24.5

For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e.

Single crystals of the mixed alkaline earth platinate, tristrontium magnesium platinum hexaoxide, Sr3MgPtO6,

were grown from a KOH ¯ux at 1273 K. The compound adopts the rhombohedral K4CdCl6 structure type, featuring

chains of face-shared, distorted MgO6trigonal prisms (Mg site

symmetry 32) and PtO6 octahedra (Pt site symmetry 3)

surrounded by columns of Sr2+_{ions (Sr site symmetry 2).}

Comment

The structure of Sr3MgPtO6was determined in 1997 (NuÂnÄezet

al., 1997) by powder X-ray diffraction on a polycrystalline sample prepared by conventional sintering techniques, and was shown to adopt the K4CdCl6structure type (Bergerhoff &

Schmitz-Dumont, 1956). This structure type features two crystallographically and chemically distinct K+ _{positions and}

consists of chains along [001] of face-shared, distorted KCl6

trigonal prisms and CdCl6octahedra. The polyhedral chains

are surrounded by spiral columns of K+_{ions. To date, a large}

and compositionally diverse group of oxides adopting this structure type has been reported, typically as polycrystalline materials [reviewed in Stitzeret al.(2001)]. High-temperature ¯ux growth from molten KOH has proven to be an effective oxide crystal growth medium. Single crystals of Sr3MgPtO6

were readily grown from molten KOH at 1273 K, using

Received 26 February 2003 Accepted 14 March 2003 Online 23 April 2003

Figure 1

Fragment of the face-shared polyhedral chains in Sr3MgPtO6.

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(NH4)2PtCl6as the platinum source. Sr3MgPtO6represents an

Mg-substituted form of the K4CdCl6-type oxide Sr4PtO6

(Randall & Katz, 1959), with Mg ordered in the trigonal prism site (site-symmetry 32, Wyckoff symbol 6a) and Pt4+ _{in a}

rhombohedrally elongated octahedral site (site symmetry 3, Wyckoff symbol 6b). Fig. 1 illustrates the local coordination of these metal centers. The Sr2+_{ion resides in an irregular}

eight-coordinate site (Wyckoff symbol 18e) of site symmetry 2. Fig. 2 shows a view of the polyhedral chains and Sr2+ _columns.

Bond lengths and angles from the present single-crystal determination of Sr3MgPtO6 are very close to those derived

from powder data [MgÐO = 2.172 (16) AÊ, PtÐO = 2.011 (16) AÊ and SrÐO = 2.498 (17)±2.742 (17) AÊ]. Re®ne-ment of the site occupancies for Mg and Pt showed no signi®cant deviation from whole occupancy, indicating a stoichiometric compound, and no Sr/Mg mixing on the trigonal prism site.

Experimental

The (NH4)2PtCl6precursor was prepared according to a published

method (Kaufman, 1967). Subsequently, SrCO3 (Alfa, 99.95%),

MgCO3(Alfa, 99.8%), and (NH4)2PtCl6(stoichiometric amounts,ca

1 g total reagent mass) and KOH (Fisher, reagent grade;10 times by mass the total reagent amount) were loaded into a covered alumina crucible. The mixture was heated at 1273 K for 2 h, cooled to 1023 K at a rate of 1 K hÿ1_{, at which point the furnace was shut off and}

allowed to cool to room temperature radiatively. The KOH matrix was dissolved with distilled water, leaving plentiful transparent brown crystals with a rhombohedral habit.

Crystal data

Sr3MgPtO6

Mr= 578.26

Trigonal,R3c

MoKradiation Cell parameters from 1132

re¯ections

Data collection

Bruker SMART APEX CCD diffractometer

!scans

Absorption correction: multi-scan

(SADABS; Bruker, 1999)

Tmin= 0.073,Tmax= 0.239

2412 measured re¯ections

490 independent re¯ections 431 re¯ections withI> 2(I)

Rint= 0.037

max= 36.3

h=ÿ16!7

k=ÿ11!16

l=ÿ18!8

Re®nement

Re®nement onF2

R[F2_{> 2}₍_F2_{)] = 0.024}

wR(F2_{) = 0.049}

S= 1.01 490 re¯ections 20 parameters

w= 1/[2₍_F

o2) + (0.0227P)2]

whereP= (Fo2+ 2Fc2)/3

(/)max< 0.001

max= 2.32 e AÊÿ3

min=ÿ3.12 e AÊÿ3

Extinction correction:SHELXL97 Extinction coef®cient: 0.00118 (8)

Table 1

Selected geometric parameters (AÊ).

SrÐO 2.472 (3)

SrÐOi _{2.637 (3)}

SrÐOii _{2.663 (3)}

SrÐOiii _{2.731 (3)}

MgÐO 2.177 (3)

MgÐPt 2.77780 (15)

PtÐO 2.031 (3)

Symmetry codes: (i) 1

3ÿxy;yÿ13;16z; (ii) 23ÿxy;13ÿx;13z; (iii) 2

3y;13ÿxy;13ÿz.

Systematic absences in the dataset con®rmed ac-glide operation, indicating the space groupsR3candR3c. Preliminary powder X-ray diffraction showed the compound to be isostructural with K4CdCl6

(space group R3c); therefore, the expected centrosymmetric space group was chosen and con®rmed by the structure solution. The largest difference peak and hole were located less than 0.8 AÊ from the Pt atom.

Data collection: SMART-NT (Bruker, 1999); cell re®nement:

SAINT-Plus-NT (Bruker, 1999); data reduction: SAINT-Plus-NT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to re®ne structure:SHELXL97 (Sheldrick, 1997); molecular graphics:ATOMS(Dowty, 2001); software used to prepare material for publication:SHELXTL(Bruker, 1997).

Funding for this research was provided by the National Science Foundation through grant DMR:0134156. The Bruker SMART APEX diffractometer was purchased using funds provided by the NSF IMR Program through grant DMR:9975623.

References

Bergerhoff, G. & Schmitz-Dumont, O. (1956).Z. Anorg. Allg. Chem.284, 10± 19.

Bruker (1997). SHELXTL. Version 5.1. Bruker AXS Inc., Madison, Wisconsin, USA.

Bruker (1999).SMART-NT(Version 5.611),SAINT-Plus-NT(Versin 6.02a)

andSADABS(Version 1.0). Bruker AXS Inc., Madison, Wisconsin, USA.

Dowty, E. (2001).ATOMS for Windows. Version 5.1. Shape Software, 521 Hidden Valley Road, Kingsport, TN 37663, USA.

Kaufman, G. S. (1967). InInorganic Syntheses, Vol. 9, edited by S. Y. Tyree Jr, pp. 182±185. New York: McGraw-Hill.

NuÂnÄez, P., Trail, S. & zur Loye, H.-C. (1997).J. Solid State Chem.130, 35±41.

Figure 2

Polyhedral view of the unit cell of Sr3MgPtO6, viewed approximately

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supporting information

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Acta Cryst. (2003). E59, i75–i76

supporting information

Acta Cryst. (2003). E59, i75–i76 [doi:10.1107/S1600536803005993]

Sr

3

MgPtO

6

Mark D. Smith and Hans-Conrad zur Loye

S1. Comment

The structure of Sr3MgPtO6 was determined in 1997 (Nùñez et al., 1997) by powder X-ray diffraction on a polycrystalline

sample prepared by conventional sintering techniques, and was shown to adopt the K4CdCl6 structure type (Bergerhoff &

Schmitz-Dumont, 1956). This structure type features two crystallographically and chemically distinct K+_{positions and}

consists of chains along [001] of face-shared distorted KCl6 trigonal prisms and CdCl6 octahedra. The polyhedral chains

are surrounded by spiral columns of K+_{ions. To date, a large and compositionally diverse group of oxides adopting this}

structure type has been reported, typically as polycrystalline materials [reviewed in Stitzer et al. (2001)].

High-temperature flux growth from molten KOH has proven to be an effective oxide crystal growth medium. Single crystals of

Sr3MgPtO6 were readily grown from molten KOH at 1273 K, using (NH4)2PtCl6 as the platinum source. Sr3MgPtO6

represents an Mg-substituted form of the K4CdCl6-type oxide Sr4PtO6 (Randall & Katz, 1959), with Mg ordered in the

trigonal prism site (site-symmetry 32, Wyckoff symbol 6a) and Pt4+_{in a rhombohedrally elongated octahedral site (site}

symmetry 3, Wyckoff symbol 6 b). Fig. 1 illustrates the local coordination of these metal centers. The Sr2+_{ion resides in}

an irregular eight coordinate site (Wyckoff symbol 18 e) of site symmetry 2. Fig. 2 shows an off-[110] view of the

polyhedral chains and Sr2+_{columns. Bond lengths and angles from the present single-crystal determination of Sr}

3MgPtO6

are very close to those derived from powder data [Mg—O = 2.172 (16) Å, Pt—O = 2.011 (16) Å and Sr—O =

2.498 (17)–2.742 (17) Å]. Refinement of the site occupancies for Mg and Pt showed no significant deviation from unity

occupancy, indicating a stoichiometric compound, and no Sr/Mg mixing on the trigonal prism site.

S2. Experimental

The (NH4)2PtCl6 precursor was prepared according to a published method (Kaufman, 1967). Subsequently, SrCO3 (Alfa,

99.95%), MgCO3 (Alfa, 99.8%), and (NH4)2PtCl6 (stoichiometric amounts, ca 1 g total reagent mass) and KOH (Fisher,

reagent grade; approx. 10 times by mass the total reagent amount) were loaded into a covered alumina crucible. The

mixture was heated at 1273 K for 2 h, cooled to 1023 K at a rate of 1 K h−1_{, at which point the furnace was shut off and}

allowed to cool to room temperature radiatively. The KOH matrix was dissolved with distilled water, leaving plentiful

transparent brown crystals with a rhombohedral habit.

S3. Refinement

Systematic absences in the dataset confirmed a c-glide operation, indicating the space groups R3c and R3c. Preliminary

powder X-ray diffraction showed the compound to be isostructural with K4CdCl6 (space group R3c); therefore, the

expected centrosymmetric space group was chosen and confirmed by the solution. The largest difference peak/hole was

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[image:4.610.180.445.69.523.2]

Figure 1

Fragment of the face-shared polyhedral chains in Sr3MgPtO6. Displacement ellipsoids are drawn at the 90% probability

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[image:5.610.129.482.69.374.2]

Acta Cryst. (2003). E59, i75–i76

Figure 2

Near-[110] polyhedral view of the unit cell of Sr3MgPtO6.

Tristrontium Magnesium Platinum Hexaoxide

Crystal data

Sr3MgPtO6 Mr = 578.26 Trigonal, R3c

Hall symbol: -R 3 2"c

a = 9.6432 (4) Å

c = 11.1112 (6) Å

V = 894.82 (7) Å3 Z = 6

F(000) = 1512

Dx = 6.439 Mg m−3

Mo Kα radiation, λ = 0.71073 Å Cell parameters from 1132 reflections

θ = 4.2–36.3°

µ = 50.13 mm−1 T = 293 K

Rhombohedron, brown 0.11 × 0.05 × 0.04 mm

Data collection

Bruker SMART APEX CCD diffractometer

Radiation source: sealed tube Graphite monochromator

ω scans

Absorption correction: multi-scan (SADABS; Bruker, 1999)

Tmin = 0.073, Tmax = 0.239

2412 measured reflections 490 independent reflections 431 reflections with I > 2σ(I)

Rint = 0.037

θmax = 36.3°, θmin = 4.2°

h = −16→7

k = −11→16

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Refinement on F2

Least-squares matrix: full

R[F2_{> 2}_σ₍_F2_{)] = 0.024} wR(F2_{) = 0.049} S = 1.01 490 reflections 20 parameters 0 restraints

Primary atom site location: structure-invariant direct methods

Secondary atom site location: difference Fourier map

w = 1/[σ2₍_F

o2) + (0.0227P)2]

where P = (Fo2_{+ 2}_Fc2_)/3

(Δ/σ)max < 0.001

Δρmax = 2.32 e Å−3

Δρmin = −3.12 e Å−3

Extinction correction: SHELXL97, Fc*_{=kFc[1+0.001xFc}2_λ3_/sin(2_θ_)]-1/4

Extinction coefficient: 0.00118 (8)

Special details

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 (Å2₎

x y z Uiso*/Ueq

Sr 0.36540 (5) 0.0000 0.2500 0.00375 (12)

Mg 0.0000 0.0000 0.2500 0.0026 (6)

Pt 0.0000 0.0000 0.0000 0.00164 (10)

O 0.1736 (4) 0.0221 (4) 0.1151 (3) 0.0059 (5)

Atomic displacement parameters (Å2₎

U11 _U22 _U33 _U12 _U13 _U23

Sr 0.00374 (18) 0.0039 (2) 0.0036 (2) 0.00197 (11) −0.00030 (8) −0.00060 (16) Mg 0.0030 (8) 0.0030 (8) 0.0017 (13) 0.0015 (4) 0.000 0.000

Pt 0.00186 (12) 0.00186 (12) 0.00122 (14) 0.00093 (6) 0.000 0.000 O 0.0062 (13) 0.0078 (14) 0.0043 (12) 0.0039 (11) −0.0030 (10) −0.0002 (10)

Geometric parameters (Å, º)

Sr—O 2.472 (3) Mg—Ptxi _{2.7778 (2)}

Sr—Oi _{2.472 (3)} _Mg—Srx _{3.5236 (5)}

Sr—Oii _{2.637 (3)} _Mg—Srxiii _{3.5236 (5)}

Sr—Oiii _{2.637 (3)} _Mg—Srxiv _{3.5865 (2)}

Sr—Oiv _{2.663 (3)} _Pt—Oxv _{2.031 (3)}

Sr—Ov _{2.663 (3)} _Pt—Oxvi _{2.031 (3)}

Sr—Ovi _{2.731 (3)} _Pt—Oxiii _{2.031 (3)}

Sr—Ovii _{2.731 (3)} _Pt—O _{2.031 (3)}

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supporting information

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Acta Cryst. (2003). E59, i75–i76

Sr—Mg 3.5236 (5) Pt—Mgxv _{2.7778 (2)}

Sr—Srix _{3.5865 (2)} _Pt—Srxviii _{3.2080 (2)}

Mg—Ox _{2.177 (3)} _Pt—Srxiv _{3.2080 (2)}

Mg—Oxi _{2.177 (3)} _Pt—Sriii _{3.2080 (2)}

Mg—Oi _{2.177 (3)} _Pt—Srxix _{3.2080 (2)}

Mg—Oxii _{2.177 (3)} _O—Sriii _{2.637 (3)}

Mg—O 2.177 (3) O—Srxx _{2.663 (3)}

Mg—Oxiii _{2.177 (3)} _O—Srxiv _{2.731 (3)}

Mg—Pt 2.7778 (2)

O—Sr—Oi _{75.35 (14)} _Oxii_—Mg—O _{146.71 (16)}

O—Sr—Oii _{94.24 (9)} _Ox_—Mg—Oxiii _{77.78 (12)}

Oi_—Sr—Oii _{76.37 (11)} _Oxi_—Mg—Oxiii _{87.89 (15)}

O—Sr—Oiii _{76.37 (11)} _Oi_—Mg—Oxiii _{146.71 (16)}

Oi_—Sr—Oiii _{94.24 (9)} _Oxii_—Mg—Oxiii _{128.62 (16)}

Oii_—Sr—Oiii _{168.27 (13)} _O—Mg—Oxiii _{77.78 (12)}

O—Sr—Oiv _{131.68 (5)} _Oxv_—Pt—Oxvi _{84.59 (13)}

Oi_—Sr—Oiv _{74.68 (12)} _Oxv_—Pt—Oxiii _{95.41 (13)}

Oii_—Sr—Oiv _{114.14 (10)} _Oxvi_—Pt—Oxiii _{180.0 (2)}

Oiii_—Sr—Oiv _{69.07 (12)} _Oxv_—Pt—O _{180.0 (2)}

O—Sr—Ov _{74.68 (12)} _Oxvi_—Pt—O _{95.41 (13)}

Oi_—Sr—Ov _{131.68 (5)} _Oxiii_—Pt—O _{84.59 (13)}

Oii_—Sr—Ov _{69.07 (12)} _Oxv_—Pt—Oxvii _{84.59 (13)}

Oiii_—Sr—Ov _{114.14 (10)} _Oxvi_—Pt—Oxvii _{84.59 (13)}

Oiv_—Sr—Ov _{150.67 (13)} _Oxiii_—Pt—Oxvii _{95.41 (13)}

O—Sr—Ovi _{122.00 (4)} _O—Pt—Oxvii _{95.41 (13)}

Oi_—Sr—Ovi _{140.32 (10)} _Oxv_—Pt—Ox _{95.41 (13)}

Oii_—Sr—Ovi _{130.498 (19)} _Oxvi_—Pt—Ox _{95.41 (13)}

Oiii_—Sr—Ovi _{61.20 (13)} _Oxiii_—Pt—Ox _{84.59 (13)}

Oiv_—Sr—Ovi _{67.69 (11)} _O—Pt—Ox _{84.59 (13)}

Ov_—Sr—Ovi _{87.93 (9)} _Oxvii_—Pt—Ox _{180.0 (2)}

O—Sr—Ovii _{140.32 (10)} _Pt—O—Mg _{82.54 (11)}

Oi_—Sr—Ovii _{122.00 (4)} _Pt—O—Sr _{170.33 (16)}

Oii_—Sr—Ovii _{61.20 (13)} _Mg—O—Sr _{98.38 (11)}

Oiii_—Sr—Ovii _{130.498 (19)} _Pt—O—Sriii _{85.80 (10)}

Oiv_—Sr—Ovii _{87.93 (9)} _Mg—O—Sriii _{95.87 (11)}

Ov_—Sr—Ovii _{67.69 (11)} _Sr—O—Sriii _{103.63 (11)}

Ovi_—Sr—Ovii _{69.64 (13)} _Pt—O—Srxx _{85.08 (10)}

Ox_—Mg—Oxi _{146.71 (16)} _Mg—O—Srxx _{167.47 (14)}

Ox_—Mg—Oi _{128.62 (16)} _Sr—O—Srxx _{93.49 (10)}

Oxi_—Mg—Oi _{77.78 (12)} _Sriii_—O—Srxx _{85.18 (9)}

Ox_—Mg—Oxii _{87.89 (15)} _Pt—O—Srxiv _{83.32 (10)}

Oxi_—Mg—Oxii _{77.78 (12)} _Mg—O—Srxiv _{93.22 (10)}

Oi_—Mg—Oxii _{77.78 (12)} _Sr—O—Srxiv _{87.02 (9)}

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Oi_—Mg—O _{87.89 (15)}