Crystal structure of Sr₂CdPt₂ containing linear platinum chains

The ternary inter­metallic title phase, distrontium cadmium diplatinum, was prepared from stoichiometric amounts of the elements at 1123 K for one day. The crystal structure adopts the ortho­rhom­bic Ca₂GaCu₂ structure type in space group Immm. Its main features are characterized by linear (Pt—Pt⋯Pt—Pt)_n chains that are aligned along [010] and condensed through cadmium atoms forming Cd-centred Pt₂Cd_2/2 rectangles to build up sheets parallel to (001). These sheets are connected to each other via alternating (001) sheets of strontium atoms along [001]. The strontium sheets consists of corrugated Sr₄ units that are condensed to each other through edge-sharing parallel to [100].

1. Chemical context

A large number of transition metal-based ternary inter­metallic phases have been studied in terms of metal–metal inter­actions and structure–property relationships (Corbett, 2010). Exploratory synthetic approaches in systems A/Cd/Pt (A = alkaline earth metal) have revealed a great compositional and structural diversity. The calcium phase Ca₆Cd₁₆Pt₈ contains a three-dimensional array of isolated Cd₈ tetra­hedral stars (TS) and a face-centred cube of Pt@Ca₆ octa­hedra (Samal et al., 2013) whilst the structure of Ca₆Cd₁₁Pt crystallizes in its own structure type consisting of apically inter­bonded Cd₇ penta­gonal bipyramids and five-membered rings of Ca atoms (Gulo et al., 2013). The strontium phase SrCd₄Pt₂ is made up of chains of edge-sharing Cd₄ tetra­hedra bridged by four-bonded Sr atoms (Samal et al., 2013) and SrCdPt presents six-membered rings of Sr atoms in a chair conformation (Gulo & Köhler, 2014). The barium phase BaCd₂Pt exhibits zigzag chains of Ba atoms and Pt-centred boat and anti-boat conformations formed by six-membered rings of Cd atoms (Gulo & Köhler, 2015). The Pt-based ternary inter­metallic compounds with general formula A₂XPt₂ (A = alkaline-earth or rare-earth metal; X = diel, triel, or tetrel element) adopt five different structure types. Sr₂InPt₂ (Muts et al., 2007) crystallizes in the monoclinic Ca₂Ir₂S type (Schoolaert & Jung, 2002), Pu₂SnPt₂ (Pereira et al., 1997) in the tetra­gonal Mo₂FeB₂ type (Gladyshevskii et al., 1996) while U₂CdPt₂ has its own structure type (Gravereau et al., 1994). Ce₂CdPt₂ (Pöttgen et al., 2000) adopts the tetra­gonal U₃Si₂ type (Zachariasen, 1948), and Ca₂CdPt₂ (Samal & Corbett, 2012) the ortho­rhom­bic Ca₂GaCu₂ type (Fornasini & Merlo, 1988).

In this article we present the crystal structure of the novel inter­metallic phase Sr₂CdPt₂ containing linear (Pt—Pt⋯Pt—Pt)_n chains as a principal structural motif.

2. Structural commentary

The ternary inter­metallic title phase adopts the ortho­rhom­bic Ca₂GaCu₂ structure type (Fornasini & Merlo, 1988) with the Ca, Ga, and Cu sites replaced by Sr, Cd, and Pt sites, respectively. The three atoms occupy three independent sites in the unit cell. The Sr atom resides on a special position with site symmetry mm2 (Wyckoff site 4 j), the Cd atom occupies a special positions with site symmetry mmm (2 a) and the Pt atom is on a special positions with site symmetry m2m (4 h). In the two structures, the transition metals (platinum and copper, respectively) occupy the same positions. In contrast, in the structure of SrCd₄Pt₂ (Samal et al., 2013) which is isotypic with ZrFe₄Si₂ (Yarmolyuk et al., 1975), the transition metals (platinum and iron, respectively) occupy different positions and the Pt atoms reside on the respective Si sites because silicon and platinum atoms are the most electronegative atoms in the two systems. The new phase Sr₂CdPt₂ contains 26 valence electrons and, as already mentioned, is isotypic with Ca₂GaCu₂. However, in comparison the structure of Sr₂CdPt₂ is appreciably distorted along the platinum chains, presumably because Ca₂GaCu₂ contains much smaller Cu atoms and a larger valence electron count of 29. Coordination spheres of each atomic site in the title structure are illustrated in Fig. 1. The Sr atom is coordinated by five other Sr, four Cd, and four Pt atoms. The Sr—Sr bond lengths vary from 3.674 (3) to 3.854 (1) Å, the Sr—Cd distances range from 3.490 (1) to 3.577 (1) Å, whereas the Sr—Pt values vary only slightly, from 3.188 (1) to 3.231 (1) Å. Six Sr atoms construct a square-planar pyramid, Sr@Sr₅. The existence of Sr—Sr strong bonds is observable in SrCdPt (Gulo & Köhler, 2014) but not in SrCd₄Pt₂ (Samal et al., 2013). The Cd atom exhibits a coordination number of twelve and has eight Sr and four Pt atoms in its environment with Cd—Pt distances of 2.785 (1) Å. The Pt atom is surrounded by six Sr, two Cd and one Pt atoms with a Pt—Pt distance of 2.734 (1) Å. This distance is slightly longer than those found in Ca₂CdPt₂ (2.659 Å; Samal & Corbett, 2012) or Sr₂InPt₂ (2.707 Å; Muts et al., 2007) but shorter than those in Pu₂SnPt₂ (Pereira et al., 1997), U₂CdPt₂ (Gravereau et al., 1994) or Ce₂CdPt₂ (Pöttgen et al., 2000). All other inter­atomic distances (Sr—Cd, Sr—Pt, and Cd—Pt) are in agreement with those found in some ternary compounds in A/Cd/Pt systems (A = alkaline earth metal).

Figure 1 Coordination of strontium, cadmium, and platinum atoms in Sr2CdPt2. Displacement ellipsoids are displayed at the 90% probability level.

3. Packing features

Sr atoms are bound together into corrugated sheets consisting of edge-sharing Sr₄-units. These sheets spread parallel to (001) and are linked by another Sr—Sr bond of 3.674 (3) Å along [001]. (Fig. 2). The crystal structure is also characterized by the existence of linear (Pt—Pt⋯Pt—Pt)_n chains along [010] with longer distances of 3.2010 (14) Å between pairs of tightly bound Pt—Pt dumbbells, a significant distortion in the direction of dimerization. The platinum chains are condensed into (001) sheets through Cd atoms, forming Cd-centred rectangles with composition Pt₂Cd_2/2 (Fig. 3). The Pt₂Cd_2/2 layers are stacked along [001] and are linked through the corrugated sheets of Sr atoms.

Figure 2 Projection of the crystal structure of Sr2CdPt2 approximately along the b axis.

Figure 3 Projection of linear platinum chains that are aligned along the b axis and condensed via cadmium atoms forming Pt2Cd2/2-rectangles in the ab-plane

4. Database survey

A search of the Pearson's Crystal Data – Crystal Structure Database for Inorganic Compounds (Villars & Cenzual, 2015) for the Sr/Cd/Pt family of compounds returned two compounds only: SrCd₄Pt₂ (Samal et al., 2013) and SrCdPt (Gulo & Köhler, 2014).

5. Synthesis and crystallization

The title compound was synthesized from starting materials of Sr granules (99.9+%, Alfa Aesar), Cd powder (99.9+%, Alfa Aesar) and Pt powder (99.95%, Chempur). A stoichiometric mixture of these elements was loaded into a Nb ampoule in an Ar-filled dry box. The Nb ampoule was then weld-sealed under an Ar atmosphere and subsequently enclosed in an evacuated silica jacket. The sample was then heated to 1123 K for 15 h, equilibrated at 923 K for 4 days, and followed by slow cooling to room temperature.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. The maximum and minimum remaining electron densities are located 1.66 and 0.81 Å, respectively, from the Pt site.

Table 1
Experimental details

Crystal data
Chemical formula	CdPt2Sr2
Mr	677.82
Crystal system, space group	Orthorhombic, Immm
Temperature (K)	293
a, b, c (Å)	4.5596 (9), 5.9351 (12), 9.1874 (18)
V (Å^3)	248.63 (9)
Z	2
Radiation type	Mo Kα
μ (mm^−1)	81.39
Crystal size (mm)	0.08 × 0.06 × 0.05
Data collection
Diffractometer	Bruker P4
Absorption correction	Multi-scan (SADABS; Bruker, 2001)
Tmin, Tmax	0.004, 0.017
No. of measured, independent and observed [I > 2σ(I)] reflections	1069, 190, 172
Rint	0.025
(sin θ/λ)max (Å^−1)	0.666
Refinement
R[F^2 > 2σ(F^2)], wR(F^2), S	0.022, 0.058, 1.16
No. of reflections	190
No. of parameters	13
Δρmax, Δρmin (e Å^−3)	1.84, −2.51
Computer programs: XSCANS (Bruker, 2001), SHELXS97 and SHELXL97 (Sheldrick, 2008) and DIAMOND (Brandenburg, 2010).

Supporting information

S1. Chemical context

A large number of transition metal-based ternary inter­metallic phases have been studied in terms of metal–metal inter­actions and structure–property relationships (Corbett, 2010). Exploratory synthetic approaches in systems Pt/Cd/A (A = alkaline earth metal) has revealed a great compositional and structural diversity. The calcium phase Ca₆Cd₁₆Pt₈ contains a three-dimensional array of isolated Cd₈ tetra­hedral stars (TS) and a face-centred cube of Pt@Ca₆ o­cta­hedra (Samal et al., 2013) whilst the structure of Ca₆Cd₁₁Pt crystallizes in its own structure type consisting of apically inter­bonded Cd₇ penta­gonal bipyramids and five-membered rings of Ca atoms (Gulo et al., 2013). The strontium phase SrCd₄Pt₂ is made up of chains of edge-sharing Cd₄ tetra­hedra bridged by four-bonded Sr atoms (Samal et al., 2013) and SrCdPt presents six-membered rings of Sr atoms in a chair conformation (Gulo & Köhler, 2014). The barium phase BaCd₂Pt exhibits zigzag chains of Ba atoms and Pt-centred boat and anti-boat conformations formed by six-membered rings of Cd atoms (Gulo & Köhler, 2015). The Pt-based ternary inter­metallic compounds with general formula A₂XPt₂ (A = alkaline-earth or rare-earth metal; X = diel, triel, or tetrel element) adopt five different structure types. Sr₂InPt₂ (Muts et al., 2007) crystallizes in the monoclinic Ca₂Ir₂S type (Schoolaert & Jung, 2002), Pu₂SnPt₂ (Pereira et al., 1997) in the tetra­gonal Mo₂FeB₂ type (Gladyshevskii et al., 1996) while U₂CdPt₂ has its own structure type (Gravereau et al., 1994). Ce₂CdPt₂ (Pöttgen et al., 2000) adopts the tetra­gonal U₃Si₂ type (Zachariasen, 1948), and Ca₂CdPt₂ (Samal & Corbett, 2012) the orthorhombic Ca₂GaCu₂ type (Fornasini & Merlo, 1988).

In this article we present the crystal structure of the novel inter­metallic phase Sr₂CdPt₂ containing linear (Pt—Pt···Pt—Pt)_n chains as a principal structural motif.

S2. Structural commentary

The ternary inter­metallic title phase adopts the orthorhombic Ca₂GaCu₂ structure type (Fornasini & Merlo, 1988) with the Ca, Ga, and Cu sites replaced by Sr, Cd, and Pt sites, respectively. The three atoms occupy three independent sites in the unit cell. The Sr atom resides on a special position with site symmetry mm2 (Wyckoff site 4 j), the Cd atom occupies a special positions with site symmetry mmm (2 a) and the Pt atom is on a special positions with site symmetry m2m (4 h). In the two structures, the transition metals (platinum and copper, respectively) occupy the same positions. In contrast, in the structure of SrCd₄Pt₂ (Samal et al., 2013) which is isotypic with ZrFe₄Si₂ (Yarmolyuk et al., 1975), the transition metals (platinum and iron, respectively) occupy different positions and the Pt atoms reside on the respective Si sites because silicon and platinum atoms are the most electronegative atoms in the two systems. The new phase Sr₂CdPt₂ contains 26 valence electrons and, as already mentioned, is isotypic with Ca₂GaCu₂. However, in comparison the structure of Sr₂CdPt₂ is appreciably distorted along the platinum chains, presumably because Ca₂GaCu₂ contains much smaller Cu atoms and a larger valence electron count of 29. Coordination spheres of each atomic site in the title structure are illustrated in Fig. 1. The Sr atom is coordinated by five other Sr, four Cd, and four Pt atoms. The Sr—Sr bond lengths vary from 3.674 (3) to 3.854 (1) Å, the Sr—Cd distances range from 3.490 (1) to 3.577 (1) Å, whereas the Sr—Pt values vary only slightly, from 3.188 (1) to 3.231 (1) Å. Six Sr atoms construct a square-planar pyramid, Sr@Sr₅. The existence of Sr—Sr strong bonds is observable in SrCdPt (Gulo & Köhler, 2014) but not in SrCd₄Pt₂ (Samal et al., 2013). The Cd atom exhibits a coordination number of twelve and has eight Sr and four Pt atoms in its environment with Cd—Pt distances of 2.785 (1) Å. The Pt atom is surrounded by six Sr, two Cd and one Pt atom with a Pt—Pt distance of 2.734 (1) Å. This distance is slightly longer than those found in Ca₂CdPt₂ (2.659 Å; Samal & Corbett, 2012) or Sr₂InPt₂ (2.707 Å; Muts et al., 2007) but shorter than those in Pu₂SnPt₂ (Pereira et al., 1997), U₂CdPt₂ (Gravereau et al., 1994) or Ce₂CdPt₂ (Pöttgen et al., 2000). All other inter­atomic distances (Sr—Cd, Sr—Pt, and Cd—Pt) are in agreement with those found in some ternary compounds in Cd/Pt/A systems (A = alkaline earth metal).

S3. Packing features

Sr atoms are bound together into corrugated sheets consisting of edge-sharing Sr₄-units. These sheets spread parallel to (001) and are linked by another Sr—Sr bond of 3.674 (3) Å along [001]. (Fig. 2). The crystal structure is also characterized by the existence of linear (Pt—Pt···Pt—Pt)_n chains along [010] with longer distances of 3.2010 (14) Å between the tightly bound Pt—Pt dumbbells, a significant distortion in the direction of dimerization. The platinum chains are condensed into (001) sheets through Cd atoms, forming Cd-centred re­cta­ngles with composition Pt₂Cd_2/2 (Fig 3). The Pt₂Cd_2/2 layers are stacked along [001] and are linked through the corrugated sheets of Sr atoms.

S4. Database survey

A search of the Pearson's Crystal Data – Crystal Structure Database for Inorganic Compounds (Villars & Cenzual, 2015) for the Sr/Cd/Pt family of compounds returned two compounds only: SrCd₄Pt₂ (Samal et al., 2013) and SrCdPt (Gulo & Köhler, 2014).

S5. Synthesis and crystallization

The title compound was synthesized from starting materials of Sr granules (99.9+%, Alfa Aesar), Cd powder (99.9+%, Alfa Aesar) and Pt powder (99.95%, Chempur). A stoichiometric mixture of these elements was loaded into a Nb ampoule in an Ar-filled dry box. The Nb ampoule was then weld-sealed under an Ar atmosphere and subsequently enclosed in an evacuated silica jacket. The sample was then heated to 1123 K for 15 h, equilibrated at 923 K for 4 days, and followed by slow cooling to room temperature.

S6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. The maximum and minimum remaining electron densities are located 1.66 and 0.81 Å, respectively, from the Pt site.

Structure description

A large number of transition metal-based ternary inter­metallic phases have been studied in terms of metal–metal inter­actions and structure–property relationships (Corbett, 2010). Exploratory synthetic approaches in systems Pt/Cd/A (A = alkaline earth metal) has revealed a great compositional and structural diversity. The calcium phase Ca₆Cd₁₆Pt₈ contains a three-dimensional array of isolated Cd₈ tetra­hedral stars (TS) and a face-centred cube of Pt@Ca₆ o­cta­hedra (Samal et al., 2013) whilst the structure of Ca₆Cd₁₁Pt crystallizes in its own structure type consisting of apically inter­bonded Cd₇ penta­gonal bipyramids and five-membered rings of Ca atoms (Gulo et al., 2013). The strontium phase SrCd₄Pt₂ is made up of chains of edge-sharing Cd₄ tetra­hedra bridged by four-bonded Sr atoms (Samal et al., 2013) and SrCdPt presents six-membered rings of Sr atoms in a chair conformation (Gulo & Köhler, 2014). The barium phase BaCd₂Pt exhibits zigzag chains of Ba atoms and Pt-centred boat and anti-boat conformations formed by six-membered rings of Cd atoms (Gulo & Köhler, 2015). The Pt-based ternary inter­metallic compounds with general formula A₂XPt₂ (A = alkaline-earth or rare-earth metal; X = diel, triel, or tetrel element) adopt five different structure types. Sr₂InPt₂ (Muts et al., 2007) crystallizes in the monoclinic Ca₂Ir₂S type (Schoolaert & Jung, 2002), Pu₂SnPt₂ (Pereira et al., 1997) in the tetra­gonal Mo₂FeB₂ type (Gladyshevskii et al., 1996) while U₂CdPt₂ has its own structure type (Gravereau et al., 1994). Ce₂CdPt₂ (Pöttgen et al., 2000) adopts the tetra­gonal U₃Si₂ type (Zachariasen, 1948), and Ca₂CdPt₂ (Samal & Corbett, 2012) the orthorhombic Ca₂GaCu₂ type (Fornasini & Merlo, 1988).

In this article we present the crystal structure of the novel inter­metallic phase Sr₂CdPt₂ containing linear (Pt—Pt···Pt—Pt)_n chains as a principal structural motif.

The ternary inter­metallic title phase adopts the orthorhombic Ca₂GaCu₂ structure type (Fornasini & Merlo, 1988) with the Ca, Ga, and Cu sites replaced by Sr, Cd, and Pt sites, respectively. The three atoms occupy three independent sites in the unit cell. The Sr atom resides on a special position with site symmetry mm2 (Wyckoff site 4 j), the Cd atom occupies a special positions with site symmetry mmm (2 a) and the Pt atom is on a special positions with site symmetry m2m (4 h). In the two structures, the transition metals (platinum and copper, respectively) occupy the same positions. In contrast, in the structure of SrCd₄Pt₂ (Samal et al., 2013) which is isotypic with ZrFe₄Si₂ (Yarmolyuk et al., 1975), the transition metals (platinum and iron, respectively) occupy different positions and the Pt atoms reside on the respective Si sites because silicon and platinum atoms are the most electronegative atoms in the two systems. The new phase Sr₂CdPt₂ contains 26 valence electrons and, as already mentioned, is isotypic with Ca₂GaCu₂. However, in comparison the structure of Sr₂CdPt₂ is appreciably distorted along the platinum chains, presumably because Ca₂GaCu₂ contains much smaller Cu atoms and a larger valence electron count of 29. Coordination spheres of each atomic site in the title structure are illustrated in Fig. 1. The Sr atom is coordinated by five other Sr, four Cd, and four Pt atoms. The Sr—Sr bond lengths vary from 3.674 (3) to 3.854 (1) Å, the Sr—Cd distances range from 3.490 (1) to 3.577 (1) Å, whereas the Sr—Pt values vary only slightly, from 3.188 (1) to 3.231 (1) Å. Six Sr atoms construct a square-planar pyramid, Sr@Sr₅. The existence of Sr—Sr strong bonds is observable in SrCdPt (Gulo & Köhler, 2014) but not in SrCd₄Pt₂ (Samal et al., 2013). The Cd atom exhibits a coordination number of twelve and has eight Sr and four Pt atoms in its environment with Cd—Pt distances of 2.785 (1) Å. The Pt atom is surrounded by six Sr, two Cd and one Pt atom with a Pt—Pt distance of 2.734 (1) Å. This distance is slightly longer than those found in Ca₂CdPt₂ (2.659 Å; Samal & Corbett, 2012) or Sr₂InPt₂ (2.707 Å; Muts et al., 2007) but shorter than those in Pu₂SnPt₂ (Pereira et al., 1997), U₂CdPt₂ (Gravereau et al., 1994) or Ce₂CdPt₂ (Pöttgen et al., 2000). All other inter­atomic distances (Sr—Cd, Sr—Pt, and Cd—Pt) are in agreement with those found in some ternary compounds in Cd/Pt/A systems (A = alkaline earth metal).

Sr atoms are bound together into corrugated sheets consisting of edge-sharing Sr₄-units. These sheets spread parallel to (001) and are linked by another Sr—Sr bond of 3.674 (3) Å along [001]. (Fig. 2). The crystal structure is also characterized by the existence of linear (Pt—Pt···Pt—Pt)_n chains along [010] with longer distances of 3.2010 (14) Å between the tightly bound Pt—Pt dumbbells, a significant distortion in the direction of dimerization. The platinum chains are condensed into (001) sheets through Cd atoms, forming Cd-centred re­cta­ngles with composition Pt₂Cd_2/2 (Fig 3). The Pt₂Cd_2/2 layers are stacked along [001] and are linked through the corrugated sheets of Sr atoms.

A search of the Pearson's Crystal Data – Crystal Structure Database for Inorganic Compounds (Villars & Cenzual, 2015) for the Sr/Cd/Pt family of compounds returned two compounds only: SrCd₄Pt₂ (Samal et al., 2013) and SrCdPt (Gulo & Köhler, 2014).

Synthesis and crystallization

The title compound was synthesized from starting materials of Sr granules (99.9+%, Alfa Aesar), Cd powder (99.9+%, Alfa Aesar) and Pt powder (99.95%, Chempur). A stoichiometric mixture of these elements was loaded into a Nb ampoule in an Ar-filled dry box. The Nb ampoule was then weld-sealed under an Ar atmosphere and subsequently enclosed in an evacuated silica jacket. The sample was then heated to 1123 K for 15 h, equilibrated at 923 K for 4 days, and followed by slow cooling to room temperature.

Refinement details

Crystal data, data collection and structure refinement details are summarized in Table 1. The maximum and minimum remaining electron densities are located 1.66 and 0.81 Å, respectively, from the Pt site.

Computing details

Data collection: XSCANS (Bruker, 2001); cell refinement: XSCANS (Bruker, 2001); data reduction: XSCANS (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2010); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. Coordination of strontium, cadmium, and platinum atoms in Sr2CdPt2. Displacement ellipsoids are displayed at the 90% probability level.
	Fig. 2. Projection of the crystal structure of Sr2CdPt2 approximately along the b axis.
	Fig. 3. Projection of linear platinum chains that are aligned parallel to b-axis direction and condensed via cadmium atoms forming Pt2Cd2/2-rectangles in the ab-plane

Distrontium cadmium diplatinum

Crystal data

CdPt2Sr2	F(000) = 560
Mr = 677.82	Dx = 9.054 Mg m^−3
Orthorhombic, Immm	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -I 2 2	Cell parameters from 25 reflections
a = 4.5596 (9) Å	θ = 12–18°
b = 5.9351 (12) Å	µ = 81.39 mm^−1
c = 9.1874 (18) Å	T = 293 K
V = 248.63 (9) Å^3	Block, brown
Z = 2	0.08 × 0.06 × 0.05 mm

Data collection

Bruker P4 4-circle diffractometer	190 independent reflections
Radiation source: fine-focus sealed tube	172 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.025
Detector resolution: 0 pixels mm^-1	θmax = 28.3°, θmin = 4.1°
ω–scans	h = −5→6
Absorption correction: multi-scan (SADABS; Bruker, 2001)	k = −7→7
Tmin = 0.004, Tmax = 0.017	l = −11→11
1069 measured reflections

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)] = 0.022	w = 1/[σ^2(Fo^2) + (0.0337P)^2 + 3.9776P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.058	(Δ/σ)max < 0.001
S = 1.16	Δρmax = 1.84 e Å^−3
190 reflections	Δρmin = −2.51 e Å^−3
13 parameters	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0024 (4)

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 (Ų)

	x	y	z	Uiso*/Ueq
Pt	0.0000	0.23034 (10)	0.5000	0.0172 (3)
Cd	−0.5000	0.5000	0.5000	0.0172 (4)
Sr	0.0000	0.5000	0.19995 (16)	0.0162 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pt	0.0156 (4)	0.0205 (4)	0.0155 (4)	0.000	0.000	0.000
Cd	0.0157 (8)	0.0152 (8)	0.0207 (9)	0.000	0.000	0.000
Sr	0.0171 (8)	0.0169 (8)	0.0146 (8)	0.000	0.000	0.000

Geometric parameters (Å, º)

Pt—Pt^i	2.7341 (13)	Cd—Sr^vii	3.4901 (10)
Pt—Cd^ii	2.7855 (5)	Cd—Sr^viii	3.5773 (12)
Pt—Cd	2.7855 (5)	Cd—Sr^iii	3.5773 (13)
Pt—Sr^iii	3.1876 (14)	Cd—Sr	3.5773 (12)
Pt—Sr	3.1876 (14)	Cd—Sr^ix	3.5773 (13)
Pt—Pt^iii	3.2010 (14)	Sr—Pt^iii	3.1876 (14)
Pt—Sr^iv	3.2312 (10)	Sr—Pt^iv	3.2312 (10)
Pt—Sr^v	3.2312 (10)	Sr—Pt^xii	3.2312 (10)
Pt—Sr^vi	3.2312 (10)	Sr—Pt^xiii	3.2312 (10)
Pt—Sr^vii	3.2312 (10)	Sr—Pt^v	3.2312 (10)
Cd—Pt^iii	2.7855 (5)	Sr—Cd^xiv	3.4901 (10)
Cd—Pt^viii	2.7855 (5)	Sr—Cd^xiii	3.4901 (10)
Cd—Pt^ix	2.7855 (5)	Sr—Cd^ii	3.5773 (12)
Cd—Sr^iv	3.4901 (10)	Sr—Sr^xv	3.674 (3)
Cd—Sr^x	3.4901 (10)	Sr—Sr^xvi	3.8535 (9)
Cd—Sr^xi	3.4901 (10)
Pt^i—Pt—Cd^ii	125.070 (13)	Sr^viii—Cd—Sr^iii	180.0
Pt^i—Pt—Cd	125.070 (13)	Pt^iii—Cd—Sr	58.560 (14)
Cd^ii—Pt—Cd	109.86 (3)	Pt^viii—Cd—Sr	121.440 (14)
Pt^i—Pt—Sr^iii	120.139 (18)	Pt^ix—Cd—Sr	121.440 (14)
Cd^ii—Pt—Sr^iii	73.232 (13)	Pt—Cd—Sr	58.560 (14)
Cd—Pt—Sr^iii	73.232 (13)	Sr^iv—Cd—Sr	66.071 (12)
Pt^i—Pt—Sr	120.139 (18)	Sr^x—Cd—Sr	113.929 (12)
Cd^ii—Pt—Sr	73.232 (13)	Sr^xi—Cd—Sr	66.071 (12)
Cd—Pt—Sr	73.232 (13)	Sr^vii—Cd—Sr	113.929 (12)
Sr^iii—Pt—Sr	119.72 (4)	Sr^viii—Cd—Sr	79.18 (3)
Pt^i—Pt—Pt^iii	180.0	Sr^iii—Cd—Sr	100.82 (3)
Cd^ii—Pt—Pt^iii	54.930 (13)	Pt^iii—Cd—Sr^ix	121.440 (14)
Cd—Pt—Pt^iii	54.930 (13)	Pt^viii—Cd—Sr^ix	58.560 (14)
Sr^iii—Pt—Pt^iii	59.861 (18)	Pt^ix—Cd—Sr^ix	58.560 (14)
Sr—Pt—Pt^iii	59.861 (18)	Pt—Cd—Sr^ix	121.440 (14)
Pt^i—Pt—Sr^iv	64.971 (13)	Sr^iv—Cd—Sr^ix	113.929 (12)
Cd^ii—Pt—Sr^iv	145.14 (2)	Sr^x—Cd—Sr^ix	66.071 (12)
Cd—Pt—Sr^iv	70.466 (13)	Sr^xi—Cd—Sr^ix	113.929 (12)
Sr^iii—Pt—Sr^iv	134.76 (2)	Sr^vii—Cd—Sr^ix	66.071 (12)
Sr—Pt—Sr^iv	73.786 (15)	Sr^viii—Cd—Sr^ix	100.82 (3)
Pt^iii—Pt—Sr^iv	115.029 (13)	Sr^iii—Cd—Sr^ix	79.18 (3)
Pt^i—Pt—Sr^v	64.971 (13)	Sr—Cd—Sr^ix	180.0
Cd^ii—Pt—Sr^v	70.466 (13)	Pt^iii—Sr—Pt	60.28 (4)
Cd—Pt—Sr^v	145.14 (2)	Pt^iii—Sr—Pt^iv	134.76 (2)
Sr^iii—Pt—Sr^v	134.76 (2)	Pt—Sr—Pt^iv	106.214 (15)
Sr—Pt—Sr^v	73.786 (15)	Pt^iii—Sr—Pt^xii	106.214 (15)
Pt^iii—Pt—Sr^v	115.029 (13)	Pt—Sr—Pt^xii	134.76 (2)
Sr^iv—Pt—Sr^v	89.75 (3)	Pt^iv—Sr—Pt^xii	50.06 (3)
Pt^i—Pt—Sr^vi	64.971 (13)	Pt^iii—Sr—Pt^xiii	106.214 (15)
Cd^ii—Pt—Sr^vi	70.466 (13)	Pt—Sr—Pt^xiii	134.76 (2)
Cd—Pt—Sr^vi	145.14 (2)	Pt^iv—Sr—Pt^xiii	110.71 (5)
Sr^iii—Pt—Sr^vi	73.786 (15)	Pt^xii—Sr—Pt^xiii	89.75 (3)
Sr—Pt—Sr^vi	134.76 (2)	Pt^iii—Sr—Pt^v	134.76 (2)
Pt^iii—Pt—Sr^vi	115.029 (13)	Pt—Sr—Pt^v	106.214 (15)
Sr^iv—Pt—Sr^vi	129.94 (3)	Pt^iv—Sr—Pt^v	89.75 (3)
Sr^v—Pt—Sr^vi	69.29 (5)	Pt^xii—Sr—Pt^v	110.71 (5)
Pt^i—Pt—Sr^vii	64.971 (13)	Pt^xiii—Sr—Pt^v	50.06 (3)
Cd^ii—Pt—Sr^vii	145.14 (2)	Pt^iii—Sr—Cd^xiv	151.90 (4)
Cd—Pt—Sr^vii	70.466 (13)	Pt—Sr—Cd^xiv	91.620 (18)
Sr^iii—Pt—Sr^vii	73.786 (15)	Pt^iv—Sr—Cd^xiv	48.779 (16)
Sr—Pt—Sr^vii	134.76 (2)	Pt^xii—Sr—Cd^xiv	93.47 (3)
Pt^iii—Pt—Sr^vii	115.029 (13)	Pt^xiii—Sr—Cd^xiv	93.47 (3)
Sr^iv—Pt—Sr^vii	69.29 (5)	Pt^v—Sr—Cd^xiv	48.779 (16)
Sr^v—Pt—Sr^vii	129.94 (3)	Pt^iii—Sr—Cd^xiii	91.620 (19)
Sr^vi—Pt—Sr^vii	89.75 (3)	Pt—Sr—Cd^xiii	151.90 (4)
Pt^iii—Cd—Pt^viii	180.0	Pt^iv—Sr—Cd^xiii	93.47 (3)
Pt^iii—Cd—Pt^ix	109.86 (3)	Pt^xii—Sr—Cd^xiii	48.779 (16)
Pt^viii—Cd—Pt^ix	70.14 (3)	Pt^xiii—Sr—Cd^xiii	48.779 (16)
Pt^iii—Cd—Pt	70.14 (3)	Pt^v—Sr—Cd^xiii	93.47 (3)
Pt^viii—Cd—Pt	109.86 (3)	Cd^xiv—Sr—Cd^xiii	116.48 (4)
Pt^ix—Cd—Pt	180.0	Pt^iii—Sr—Cd^ii	48.21 (2)
Pt^iii—Cd—Sr^iv	119.245 (13)	Pt—Sr—Cd^ii	48.21 (2)
Pt^viii—Cd—Sr^iv	60.755 (13)	Pt^iv—Sr—Cd^ii	152.59 (2)
Pt^ix—Cd—Sr^iv	119.245 (13)	Pt^xii—Sr—Cd^ii	152.59 (2)
Pt—Cd—Sr^iv	60.755 (13)	Pt^xiii—Sr—Cd^ii	89.339 (16)
Pt^iii—Cd—Sr^x	60.755 (13)	Pt^v—Sr—Cd^ii	89.339 (16)
Pt^viii—Cd—Sr^x	119.245 (13)	Cd^xiv—Sr—Cd^ii	113.929 (12)
Pt^ix—Cd—Sr^x	60.755 (13)	Cd^xiii—Sr—Cd^ii	113.929 (12)
Pt—Cd—Sr^x	119.245 (13)	Pt^iii—Sr—Cd	48.21 (2)
Sr^iv—Cd—Sr^x	180.00 (4)	Pt—Sr—Cd	48.21 (2)
Pt^iii—Cd—Sr^xi	60.755 (13)	Pt^iv—Sr—Cd	89.339 (16)
Pt^viii—Cd—Sr^xi	119.245 (13)	Pt^xii—Sr—Cd	89.339 (16)
Pt^ix—Cd—Sr^xi	60.755 (13)	Pt^xiii—Sr—Cd	152.59 (2)
Pt—Cd—Sr^xi	119.245 (13)	Pt^v—Sr—Cd	152.59 (2)
Sr^iv—Cd—Sr^xi	116.48 (4)	Cd^xiv—Sr—Cd	113.929 (12)
Sr^x—Cd—Sr^xi	63.52 (4)	Cd^xiii—Sr—Cd	113.929 (12)
Pt^iii—Cd—Sr^vii	119.245 (13)	Cd^ii—Sr—Cd	79.18 (3)
Pt^viii—Cd—Sr^vii	60.755 (13)	Pt^iii—Sr—Sr^xv	149.861 (18)
Pt^ix—Cd—Sr^vii	119.245 (13)	Pt—Sr—Sr^xv	149.861 (18)
Pt—Cd—Sr^vii	60.755 (13)	Pt^iv—Sr—Sr^xv	55.35 (2)
Sr^iv—Cd—Sr^vii	63.52 (4)	Pt^xii—Sr—Sr^xv	55.35 (2)
Sr^x—Cd—Sr^vii	116.48 (4)	Pt^xiii—Sr—Sr^xv	55.35 (2)
Sr^xi—Cd—Sr^vii	180.0	Pt^v—Sr—Sr^xv	55.35 (2)
Pt^iii—Cd—Sr^viii	121.440 (14)	Cd^xiv—Sr—Sr^xv	58.24 (2)
Pt^viii—Cd—Sr^viii	58.560 (14)	Cd^xiii—Sr—Sr^xv	58.24 (2)
Pt^ix—Cd—Sr^viii	58.560 (14)	Cd^ii—Sr—Sr^xv	140.409 (17)
Pt—Cd—Sr^viii	121.440 (14)	Cd—Sr—Sr^xv	140.409 (17)
Sr^iv—Cd—Sr^viii	66.071 (12)	Pt^iii—Sr—Sr^xvi	53.63 (3)
Sr^x—Cd—Sr^viii	113.929 (12)	Pt—Sr—Sr^xvi	100.38 (5)
Sr^xi—Cd—Sr^viii	66.071 (12)	Pt^iv—Sr—Sr^xvi	151.51 (5)
Sr^vii—Cd—Sr^viii	113.929 (12)	Pt^xii—Sr—Sr^xvi	103.14 (3)
Pt^iii—Cd—Sr^iii	58.560 (14)	Pt^xiii—Sr—Sr^xvi	52.59 (2)
Pt^viii—Cd—Sr^iii	121.440 (14)	Pt^v—Sr—Sr^xvi	92.53 (2)
Pt^ix—Cd—Sr^iii	121.440 (14)	Cd^xiv—Sr—Sr^xvi	141.30 (3)
Pt—Cd—Sr^iii	58.560 (14)	Cd^xiii—Sr—Sr^xvi	58.05 (2)
Sr^iv—Cd—Sr^iii	113.929 (12)	Cd^ii—Sr—Sr^xvi	55.88 (3)
Sr^x—Cd—Sr^iii	66.071 (12)	Cd—Sr—Sr^xvi	101.13 (5)
Sr^xi—Cd—Sr^iii	113.929 (12)	Sr^xv—Sr—Sr^xvi	103.81 (4)
Sr^vii—Cd—Sr^iii	66.071 (12)

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