Two phases of bis­(tetraethyl­ammonium) di-μ-chloro-bis­[di­chloro­palladium(II)]

A phase transition was found to occur at ∼153 K in the title compound, (C₈H₂₀N)₂[PdCl₆]. The structures of the two phases are reported at 292 and 130 K. The low-temperature phase is twinned. The phase transition is accompanied by a minor displacement of the ions. There are C—H...Cl interactions as short as ∼2.80 Å, indicating the existence of hydrogen bonds, and this was confirmed by vibrational spectroscopy. The [Pd₂Cl₆]²⁻ anion occupies sites of mmm and 2/m symmetry in the room-temperature and low-temperature phases, respectively.

S1. Comment

The present study was prompted by the occurrence of phase transitions in chemically related compounds, for example (NH₄)₂PdCl₄ (e.g. Adams & Berg, 1976; Prager & Badurek, 1986; Gesi, 2001) and [N(CH₃)₄]₂PdCl₄ (e.g. Sato et al., 1987; Vaněk et al., 1993; Fábry et al., 2004). Larger cations can cause condensation of [PdCl₄]²⁻ into [Pd₂Cl₆]²⁻ or even larger anions, as in Cs₂Pd₂Cl₆ (Schüpp & Keller, 1999) or [N(C₄H₉)₄]₂Pd₂Cl₆ (Bouquillon et al., 1999). These latter authors isolated a mononuclear compound, [N(C₄H₉)₄]₂PdCl₄, in the form of a powder from which [N(C₄H₉)₄]₂Pd₂Cl₆ was recrystallized.

The aim of the present study was the preparation of bis(tetraethylammonium) tetrachloropalladium(II), (Et₄N)₂PdCl₄, or of Pd₂Cl₄(µ-Cl)₂(Et₄N)₂, the detection of plausible phase transitions in the prepared compound, and the structure determination of pertinent phases. The structure analyses at 292 K and 130 K showed that the sample under study corresponded to the latter formula, the title compound, (I). The structural motifs and views of the unit cells of the low- and room-temperature structures are shown in Figs. 1 and 2.

A phase transition was detected by differential scanning calorimetry at ~153 K, as well as by the splitting of reflections except those of the 0kl type below the phase transition temperature (see Experimental). The phase transition is accompanied by a change of the crystal system from orthorhombic to monoclinic during cooling. To facilitate the comparison of the two phases, the low-temperature phase is described in the space group I2/m, a non-standard setting of C2/m. The lattice parameters relating to the standard space-group setting and the corresponding coordinates are included in the archived CIF, as is a detailed description of the twinning which was observed in the low-temperature phase.

The geometrical parameters of the [Pd₂Cl₆]²⁻ anion in (I) (Tables 1 and 2) correspond very well with the values obtained from nine compounds found in the Cambridge Structural Database (CSD, November 2002 release, version 5.24, and addenda up to the end of 2003; Allen, 2002), as well as with those of the only inorganic structure known to contain the [Pd₂Cl₆]²⁻ anion, Cs₂Pd₂Cl₆ (Schüpp & Keller, 1999). In these structures, the [Pd₂Cl₆]²⁻ anion is usually situated on an element of symmetry; most often it lies across a centre of inversion, in accordance with Kitaigorodskii's rule (Kitaigorodskii, 1955). However, in [N(C₄H₉)₄]₂Pd₂Cl₆ (Bouquillon et al., 1999), the anion occupies a general position in space group P1.

In the title structures, the [Pd₂Cl₆]²⁻ anion occupies sites of mmm and 2/m symmetry in the room-temperature and low-temperature phases, respectively. Therefore the anion is strictly planar, in accordance with the findings by Pérez et al. (2002), who observed that the [Pd₂(µ-Cl)₂] core is usually planar.

In the studied structures, the ethyl group containing atoms C1 and C3 (atoms C5 and C6 in the low-temperature phase) differs from that containing atoms C2 and C4 by its orientation with respect to the [Pd₂Cl₆]²⁻ anion. Consequently, these pairs of ethyl groups interact differently with the Cl atoms. The equivalent displacement parameters, U_eq, of atoms C1 and C3 are somewhat higher than those of the respective atoms C2 and C4 or C5 and C6, especially in the room-temperature phase (Table 5, Fig. 2). The displacement parameters of the methyl C atoms are larger than those of the methylene C atoms, in accordance with expectations. On the other hand, the C—C distances are somewhat shorter in the high-temperature phase than the corresponding distances in the low-temperature phase (Tables 1 and 3). This indicates libration of the methyl groups.

It can be deduced that these features may be related to the phase transition. The phase transition is accompanied by displacements of the atoms by several tenths of an Ångstøm and by a moderate rotation of the methyl group around the C2—C4 bond by several degrees. These changes in the geometric parameters are concomitant with the disappearance of some mirror planes in accordance with the change of symmetry of the room- and low-temperature phases. The sections of the difference electron density maps through the methyl H atoms show ordered methyl groups at room temperature. At low temperature, the difference electron density map is not so clear, due to the twinning and hence the rejection of some unmatching reflections, as well as due to errors in data collection caused by the twinning. Despite this, the methyl H atoms also seem to be ordered in the low temperature phase.

As a result of the phase transition, some H atoms are closer to the Cl atoms at low temperature (cf. Tables 2 and 4). It is worthwhile stressing that the methylene H atoms are closer to the Cl atoms than the methyl H atoms. This situation is similar to that in [N(C₄H₉)₄]₂Pd₂Cl₆ (Bouquillon et al., 1999). In the latter structure, the closest H_methylene···Cl distance is 2.5767 (7) Å, while the closest H_methyl···Cl distance is 3.1455 (7) Å.

The shortest C—H···Cl distances and angles in (I) indicate the existence of hydrogen bonds which can be considered as intermediate or long, even for the N—H···Cl moiety (i.e. with a more electronegative donor), where the Cl atom is bonded to a metal (Desiraju & Steiner, 1999; Aullón et al., 1998). Some H atoms, such as H12 (Table 2) and H12 and H22 (Table 4), are involved in a bifurcated interaction with the surrounding Cl atoms. The vibrational spectroscopic data can serve as the criterion (e.g. James et al., 1996) for deciding whether a hydrogen bond really exists, due to a decrease in a pertinent frequency of a D···H bond. Therefore, both IR and Raman spectra were recorded in order to confirm the existence of C—H···Cl hydrogen bonds in the title crystal structures (see Experimental). The observed lowering of the ν_asCH₂ frequencies is clear evidence of the formation of C—H···Cl hydrogen bonds.

Tables 2 and 4 The shortest H···Cl interactions up to 3.5 Å

Table 5 Equivalent displacement parameters U_eq (Ų); U_eq = Σ_iΣ_jU^ija^*_ia^*_ja_ia_j of the room- and low-temperature phases of the title structures and their ratio.

S2. Experimental

Our intention was to prepare [N(C₂H₅)₄][PdCl₄] from stoichiometric amounts of [N(C₂H₅)]₄Cl and PdCl₂ according to the following equations: [N(C₂H₅)]₄OH + HCl → [N(C₂H₅)]₄Cl + H₂O (1) 2[N(C₂H₅)]₄Cl + PdCl₂ → [N(C₂H₅)]₂[PdCl₄] (2) Accordingly, aqueous [N(C₂H₅)₄]OH (2.3767 M; Aldrich) was neutralized with a stoichiometric amount of HCl (Lachema) to yield [N(C₂H₅)₄]Cl (2 g). A stoichiometric amount of PdCl₂ (1.070 g; Fluka) was then added to the solution; the colour of the solution changed to dark-red-brown during dissolution of the PdCl₂. Water was added to bring the volume of the mixture to 300 ml and it was allowed to stand for 12 h. The mixture was then stirred for 2 h in order to dissolve all remaining solid matter, followed by heating to 323 (5) K for another 2 h. The resulting wine-red solution (about 50 ml) was decanted into another beaker in order to obtain the red-brown precipitate. Water (about 45 ml) was then added and all solid matter dissolved. After one month at 292 (2) K, crystals of (I) several mm in size were formed. The preparation was successfully repeated with stoichiometric amounts of the reagents, according to the reaction 2[N(C₂H₅)₄]Cl + 2PdCl₂ → [N(C₂H₅)₄]₂Pd₂Cl₆. In all the cases the lattice parameters corresponded to the phase that is described in this article.

The calorimetric experiments were performed on a PerkinElmer DSC 7 differential scanning calorimeter using Pyris Software (PerkinElmer, 2001), with m = 28 mg, a temperature interval of 93–323 K and a scanning rate of 10 K min⁻¹. The experiment showed a λ-type anomaly which indicated a structural phase transition at about 153 K. A melting point was detected at 449 K, ΔH = 57 J g⁻¹. The structural phase transition was observed even in previously melted and solidified samples. After several cycles of cooling and heating, the phase-transition temperature tended to be lower by 2–4 K, according to three experiments on different samples.

The phase transition was also recognized by the splitting of reflections on several single crystals. Preliminary measurements showed that the reflections hk0 were split, while 0kl were not. By careful centring of the reflections using narrow slits on the point detector, it was possible to determine the lattice parameters with the prevailing contribution to the diffraction of just one of the domain states.

The orientation matrices relating the respective domain states of the low-temperature phase were determined experimentally and correspond well with an idealized twinning matrix:

$ λeft(µatrix{h_{2} & k_{2} & l_{2}ρight) = λeft(µatrix{h_{1} & k_{1} & l_{1}ρight) πmatrix {−1 & 0 & -(2c/a)χos(βeta) χr 0 & −1 & 0 χr 0 & 0 & 1 χr}}$

Finally, the reversibility of the phase transition was determined experimentally. After collecting data on the low-temperature phase, the data collection of the room temperature phase proved reversibility of the phase transition. (The room-temperature phase was determined on several crystals.)

The IR and Raman spectra were recorded on a Nicolet Magna 760 FTIR spectrometer equipped with a Nicolet Nexus FT Raman module. The spectra were collected under the following conditions: IR spectrum: fluorolube mull, 2 cm⁻¹ resolution, 32 scans, Happ-Genzel apodization; Raman spectrum: polycrystalline sample in glass vial, 2 cm⁻¹ resolution, 512 scans, Happ-Genzel apodization, 400 mW N d:YVO4 laser excitation at 1064 nm, 292 K. Our attention was focused on four observed bands of C—H stretching vibrations. According to a previous spectroscopic study of tetraethylammonium salts (Baran et al., 2000), these bands were assigned to ν_asCH₃ (IR 3006 cm⁻¹, w; Ra 3002 cm⁻¹, sh), ν_asCH₃ (IR 2984 cm⁻¹, s; Ra 2986 cm⁻¹, versus), ν_asCH₂ (IR 2973 cm⁻¹, sh; Ra 2968 cm⁻¹ m), and ν_asCH₂ (IR 2946 cm⁻¹, m; Ra 2939 cm⁻¹, versus) vibrations. The frequencies of these bands are shifted to lower wavenumbers in both IR (4–10 cm⁻¹) and Raman spectra (10–16 cm⁻¹) compared with [N(C₄H₉)₄]HSeO₄ (Baran et al., 2000), but are similar to the values found in Please check amended text [N(C₄H₉)₄]SbCl₆ (Zeegers-Huyskens & Bator, 1996) and [N(C₄H₉)₄]Cl·4H₂O (Baran et al., 2000).

S3. Refinement

Refinement of the low-temperature data was performed on a data set composed of two merged sets of reflections which originated from the domains pertinent to each respective domain state. The exactly superimposed reflections which stem from the domains of both domain states are 0 k l, in accordance with the twinning matrix

$ λeft(µatrix{h_{2} & k_{2} & l_{2}ρight) = λeft(µatrix{h_{1} & k_{1} & l_{1}ρight) πmatrix {−1 & 0 & -(2c/a)χos(βeta) χr 0 & −1 & 0 χr 0 & 0 & 1 χr}$

The respective reflections linked by the orientation matrix refer to the first and second domain states. The refinement program JANA2000 (Petříček & Dušek, 2000) accounts for the systematic superposition of the reflections that occur in accordance with the twinning matrix. The refined domain-state fraction resulted in a value of 0.5008 (9). (The data for each domain state were measured with a standard reflection 006, which is common to both domain states, in order to facilitate further scaling. See the archived CIF for further details.) The extinction correction turned out to be insignificant both for the room- and low-temperature phases.

From the refinement of the low-temperature phase were omitted 125 unmatched reflections for which |F_o²-F_c²| > 3σ(F_o²). The reason for the rejection of these unmatched reflections was innappropriately high indicators for the refinement on 2226 reflections of which 1444 were considered observed [I > 3σ(I)]: R_obs = 0.0472, Rw_obs = 0.1246, R_all = 0.0974 and Rw_all = 0.1324, S_all = 2.08, S_obs = 2.45, and ρ_max = 1.69 and ρ_min = −1.69 e Å⁻³. Otherwise the conditions of the refinement were the same as those reported above for the sample at 130 K. From a comparison of the refined parameters of the non-H atoms in both models, it followed that the absolute value of their differences divided by the average of the standard uncertainties did not exceed 5.5 in unique cases.

In order to explain the differences between the observed and calculated intensities of the rejected reflections, it was found that some of these reflections were either split (1 0 3) or their profile was unsymmetric. The indices of many rejected reflections were of the type 1 0 l or 1 0 ¯l. Therefore, it was taken into account that the reason for the rejection of these reflections may be the imperfect superposition of the reflections. Consequently, an alternative procedure was adopted, applying the function checkran in JANA2000. This function calculates the positions of the corresponding reflections stemming from the other domain state for each measured reflection in a bisecting position, taking as its input the orientation matrices pertinent to each domain state.

If the differences |Δχ|, |Δω| and |Δθ| in the setting angles of both reflections were simultaneously lower than 0.7, 0.10 and 0.10°, respectively, then such reflecctions were considered to be fully overlapped. On the other hand, if at least one of these respective differences of the setting angles was greater than 1.9, 0.15 or 0.15°, then such a reflection was considered to be fully separated. The remaining reflections were considered to be imperfectly separated and were therefore not included in further refinement. The values of the limits for the setting angles were determined by a series of refinements with varying values of these limits. The criteria for adopting the values of the setting-angle limits were the lowest indicators of the refinement. These trial refinements were performed on a data set which was averaged only through the inversion. In the next stage, the reflections which were considered imperfectly overlapped were discarded from the reflection list. Each of the reflection subsets was averaged through the symmetry operations of 2/m. Hence the refinement of 2152 diffractions of which 1382 were observed [I > 3σ(I)] resulted in R_obs = 0.0350, Rw_obs = 0.0824, R_all = 0.0886 and Rw_all = 0.0938, S_all = 1.46, S_obs = 1.61, and ρ_max = 0.71 and ρ_min = −0.49 e Å⁻³. Otherwise the conditions of the refinement were the same as those reported above for (I) at 130 K. This means that the result of the refinement on the data processed by checkran is inferior to that given above for (I) at 292 K, where the unmatched reflections were simply discarded from the refinement.

From the comparison of the corresponding positional and displacement parameters of the non-H atoms in both models, it followed that the absolute value of their differences divided by the average of the standard uncertainties did not exceed 2.5 and 4.75, respectively, in unique cases. Therefore neither structure model is influenced too much by omission of the reflections. Thus the model with the lower R factor is given preference and reported in this article, despite the fact that the rejection of the reflections has not been fully explained.

The structures of the room-temperature and low-temperature phases were determined on different samples. After collecting data on the low-temperature phase, data collection on the room temperature phase proved the reversibility of the phase transition.

H atoms were placed in geometric positions and treated as riding, with C—H distances in the range 0.96–0.97 Å and with U_iso(H) = 1.2U_eq(C). Please check added text.

Computing details

For both compounds, data collection: KM4B8 (Gałdecki et al., 1997); cell refinement: KM4B8; data reduction: JANA2000 (Petříček & Dušek, 2000); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: JANA2000; molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: JANA2000.

Figures

	Fig. 1. A view of the unit cell of (I) at 292 K, along the c axis. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. A view of the unit cell of (I) at 130 K, along the b axis b. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.

(I_at_292K) bis(tetraethylammonium) di-µ-chloro-bis[dichloropalladium(II)]

Crystal data

(C8H20N)2[Pd2Cl6]	F(000) = 688
Mr = 686.04	Dx = 1.585 Mg m^−3
Orthorhombic, Immm	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: -I 2 2	Cell parameters from 30 reflections
a = 8.7922 (12) Å	θ = 5.7–14.0°
b = 12.3094 (16) Å	µ = 1.81 mm^−1
c = 13.2806 (19) Å	T = 292 K
V = 1437.3 (3) Å^3	Plate with a trigonal base, red
Z = 2	0.24 × 0.18 × 0.12 mm

Data collection

Kuma XCalibur diffractometer	668 reflections with I > 3σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.029
Graphite monochromator	θmax = 27.0°, θmin = 2.3°
ω/2θ scans	h = −11→11
Absorption correction: gaussian JANA2000 (Petříček & Dušek, 2000)	k = −15→15
Tmin = 0.676, Tmax = 0.737	l = −16→16
6309 measured reflections	3 standard reflections every 100 reflections
919 independent reflections	intensity decay: 2.8%

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)] = 0.025	Hydrogen site location: difference Fourier map
wR(F^2) = 0.073	H-atom parameters constrained
S = 1.61	Weighting scheme based on measured s.u.'s w = 1/[σ^2(I) + 0.0009I^2]
919 reflections	(Δ/σ)max = 0.002
43 parameters	Δρmax = 0.40 e Å^−3
0 restraints	Δρmin = −0.24 e Å^−3
22 constraints

Special details

Refinement. Refinement of F² against ALL reflections. The H atoms were restrained and constrained.

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

	x	y	z	Uiso*/Ueq
Pd	0.5	0.36236 (3)	0.5	0.06391 (15)
N	0.5	0.0	0.7478 (3)	0.0687 (14)
C1	0.3631 (5)	0.0	0.6782 (4)	0.0956 (18)
C2	0.5	0.0980 (3)	0.8170 (3)	0.0792 (13)
C3	0.2123 (6)	0.0	0.7272 (5)	0.134 (3)
C4	0.5	0.2067 (3)	0.7671 (4)	0.102 (2)
Cl1	0.68081 (16)	0.5	0.5	0.0823 (5)
Cl2	0.31118 (14)	0.23685 (9)	0.5	0.0987 (4)
H11	0.3699	−0.0604	0.6328	0.1147*
H12	0.5846	0.0933	0.8625	0.0951*
H13	0.1335	0.0	0.6761	0.1607*
H23	0.2022	−0.0643	0.7688	0.1607*
H14	0.5	0.2632	0.8179	0.123*
H24	0.5901	0.2137	0.7254	0.123*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pd	0.0761 (3)	0.0616 (2)	0.0540 (2)	0.0	0.0	0.0
N	0.070 (3)	0.064 (2)	0.072 (2)	0.0	0.0	0.0
C1	0.107 (4)	0.083 (3)	0.096 (3)	0.0	−0.028 (3)	0.0
C2	0.078 (2)	0.081 (2)	0.079 (2)	0.0	0.0	−0.009 (2)
C3	0.080 (3)	0.145 (5)	0.176 (6)	0.0	−0.042 (4)	0.0
C4	0.117 (4)	0.073 (2)	0.118 (4)	0.0	0.0	−0.014 (3)
Cl1	0.0680 (8)	0.0738 (8)	0.1052 (10)	0.0	0.0	0.0
Cl2	0.1043 (8)	0.0755 (7)	0.1165 (8)	−0.0215 (6)	0.0	0.0

Geometric parameters (Å, º)

Pd—Cl1	2.3233 (9)	C1—H11	0.960
Pd—Cl1^i	2.3233 (9)	C1—H11^iv	0.960
Pd—Cl2	2.2679 (11)	C2—H12	0.960
Pd—Cl2^ii	2.2679 (11)	C2—H12^ii	0.960
N—C1	1.518 (5)	C3—H13	0.970
N—C1^iii	1.518 (5)	C3—H23	0.970
N—C2	1.517 (4)	C3—H23^iv	0.970
N—C2^iii	1.517 (4)	C4—H14	0.970
C1—C3	1.473 (7)	C4—H24	0.970
C2—C4	1.495 (6)	C4—H24^ii	0.970
Cl1—Pd—Cl1^i	86.35 (4)	C1^iii—N—C2^iii	111.66 (11)
Cl1—Pd—Cl2	176.12 (4)	C2—N—C2^iii	105.3 (3)
Cl1—Pd—Cl2^ii	89.77 (4)	C2^iii—N—C2	105.3 (3)
Cl1^i—Pd—Cl1	86.35 (4)	N—C1—C3	116.4 (4)
Cl1^i—Pd—Cl2	89.77 (4)	N—C2—C4	116.4 (3)
Cl1^i—Pd—Cl2^ii	176.12 (4)	H11—C1—H11^iv	101.5
Cl2—Pd—Cl2^ii	94.12 (4)	H12—C2—H12^ii	101.6
Cl2^ii—Pd—Cl2	94.12 (4)	H13—C3—H23	109.5
C1—N—C1^iii	105.0 (3)	H13—C3—H23^iv	109.5
C1—N—C2	111.66 (11)	H23—C3—H23^iv	109.5
C1—N—C2^iii	111.66 (11)	H14—C4—H24	109.5
C1^iii—N—C1	105.0 (3)	H14—C4—H24^ii	109.5
C1^iii—N—C2	111.66 (11)	H24—C4—H24^ii	109.5

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1, y, z; (iii) −x+1, −y, z; (iv) x, −y, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H11···Cl2^v	0.96	2.84	3.783 (3)	166
C2—H12···Cl1^vi	0.96	2.98	3.903 (3)	161
C2—H12···Cl2^vii	0.96	3.42	4.186 (3)	139
C3—H23···Cl1^viii	0.97	3.18	3.636 (7)	111
C4—H24···Cl2^ii	0.97	3.13	3.935 (5)	141

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

(I_at_130K) bis(tetraethylammonium) di-µ-chloro-bis[dichloropalladium(II)]

Crystal data

(C8H20N)2[Pd2Cl6]	F(000) = 688
Mr = 686.04	The choice of the unit cell is non-standard to enable easier comparison with the parent high-temperature phase. A unit-cell for the standard setting C 1 2/m 1 can be obtained by a following transformation: #_diffrn_reflns_transf_matrix_11 -1 #_diffrn_reflns_transf_matrix_12 0 #_diffrn_reflns_transf_matrix_13 1 #_diffrn_reflns_transf_matrix_14 0 #_diffrn_reflns_transf_matrix_15 1 #_diffrn_reflns_transf_matrix_16 0 #_diffrn_reflns_transf_matrix_17 -1 #_diffrn_reflns_transf_matrix_18 0 #_diffrn_reflns_transf_matrix_19 0 The corresponding standard unit-cell, compatible with C 1 2/m 1, is #_cell_length_a 15.4562(28) #_cell_length_b 12.2375(28) #_cell_length_c 8.7249(12) #_cell_angle_alpha 90 #_cell_angle_beta 122.371(17) #_cell_angle_gamma 90 #_cell_volume 1393.8(5) #_cell_formula_units_Z 2 and the space-group type is as follows: #_symmetry_cell_setting monoclinic #_symmetry_space_group_name_H-M 'C 1 2/m 1' #_symmetry_space_group_name_Hall '-C 2y' #_space_group_IT_number 12 The corresponding atomic parameters described in C 1 2/m 1 are : #======================================================================= ## 9. ATOMIC COORDINATES AND DISPLACEMENT PARAMETERS # #loop_ # _atom_site_label # _atom_site_type_symbol # _atom_site_fract_x # _atom_site_fract_y # _atom_site_fract_z # _atom_site_adp_type # _atom_site_U_iso_or_equiv # _atom_site_symmetry_multiplicity # _atom_site_occupancy # _atom_site_calc_flag # _atom_site_refinement_flags # _atom_site_disorder_assembly # _atom_site_disorder_group # Pd Pd 0.5 0.36120(4) 1 Uani 0.0288(2) 4 1 d . . . # N N 0.2525(3) 0.0 0.7286(6) Uani 0.030(2) 4 1 d . . . # C1 C 0.3164(4) 0.0 0.6459(8) Uani 0.036(3) 4 1 d . . . # C2 C 0.1826(3) 0.0990(3) 0.6700(5) Uani 0.0318(19) 8 1 d . . . # C3 C 0.2594(5) 0.0 0.4407(8) Uani 0.048(4) 4 1 d . . . # C4 C 0.2347(3) 0.2089(3) 0.7198(6) Uani 0.042(2) 8 1 d . . . # C5 C 0.3285(5) 0.0 0.9308(8) Uani 0.039(3) 4 1 d . . . # C6 C 0.2845(5) 0.0 1.0475(9) Uani 0.054(4) 4 1 d . . . # Cl1 Cl 0.49074(11) 0.5 1.17223(18) Uani 0.0343(7) 4 1 d . . . # Cl2 Cl 0.50676(9) 0.23448(9) 0.81494(15) Uani 0.0413(6) 8 1 d . . . # H11 H 0.3632 -0.0605 0.6929 Uiso 0.0437 8 1 d . . . # H12 H 0.1388 0.0931 0.7165 Uiso 0.0382 8 1 d . . . # H22 H 0.1341 0.096 0.5414 Uiso 0.0382 8 1 d . . . # H13 H 0.3083 0.0 0.4033 Uiso 0.0573 4 1 d . . . # H23 H 0.2168 -0.0647 0.3937 Uiso 0.0573 8 1 d . . . # H14 H 0.1835 0.2661 0.6792 Uiso 0.0499 8 1 d . . . # H24 H 0.281 0.2133 0.8504 Uiso 0.0499 8 1 d . . . # H34 H 0.2731 0.218 0.6618 Uiso 0.0499 8 1 d . . . # H15 H 0.3743 0.0608 0.9631 Uiso 0.0467 8 1 d . . . # H16 H 0.3397 0.0 1.1743 Uiso 0.0643 4 1 d . . . # H26 H 0.2427 0.0647 1.022 Uiso 0.0643 8 1 d . . . # #loop_ # _atom_site_aniso_label # _atom_site_aniso_type_symbol # _atom_site_aniso_U_11 # _atom_site_aniso_U_22 # _atom_site_aniso_U_33 # _atom_site_aniso_U_12 # _atom_site_aniso_U_13 # _atom_site_aniso_U_23 # Pd Pd 0.0268(2) 0.0275(2) 0.0301(3) 0.0 0.01399(19) 0.0 # N N 0.031(3) 0.030(3) 0.030(3) 0.0 0.017(2) 0.0 # C1 C 0.033(3) 0.032(3) 0.053(4) 0.0 0.029(3) 0.0 # C2 C 0.031(2) 0.0321(19) 0.034(2) 0.0061(16) 0.0191(19) 0.0033(16) # C3 C 0.066(4) 0.051(4) 0.048(4) 0.0 0.046(4) 0.0 # C4 C 0.043(3) 0.033(2) 0.048(3) 0.0040(18) 0.023(2) 0.003(2) # C5 C 0.042(3) 0.035(3) 0.032(4) 0.0 0.014(3) 0.0 # C6 C 0.054(4) 0.064(5) 0.028(4) 0.0 0.012(4) 0.0 # Cl1 Cl 0.0441(8) 0.0337(8) 0.0339(9) 0.0 0.0267(7) 0.0 # Cl2 Cl 0.0505(7) 0.0336(6) 0.0416(8) 0.0007(4) 0.0258(6) -0.0054(4) # #=======================================================================
Monoclinic, I2/m	Dx = 1.634 Mg m^−3
Hall symbol: -I 2y	Mo Kα radiation, λ = 0.71069 Å
a = 8.7249 (12) Å	Cell parameters from 39 reflections
b = 12.238 (3) Å	θ = 6.8–12.8°
c = 13.062 (2) Å	µ = 1.87 mm^−1
β = 91.973 (17)°	T = 130 K
V = 1393.8 (4) Å^3	Prism, red
Z = 2	0.25 × 0.14 × 0.12 mm

Data collection

Kuma XCalibur diffractometer	1326 reflections with I > 3σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.113
Graphite monochromator	θmax = 27.0°, θmin = 2.3°
ω/2θ scans	h = −11→11
Absorption correction: gaussian JANA2000 (Petříček & Dušek, 2000)	k = −15→15
Tmin = 0.741, Tmax = 0.820	l = −16→16
7138 measured reflections	3 standard reflections every 100 reflections
2101 independent reflections	intensity decay: 1.8%

Refinement

Refinement on F^2	42 constraints
R[F^2 > 2σ(F^2)] = 0.029	H-atom parameters constrained
wR(F^2) = 0.075	Weighting scheme based on measured s.u.'s w = 1/[σ^2(I) + 0.0009I^2]
S = 1.15	(Δ/σ)max = 0.0003
1986 reflections	Δρmax = 0.43 e Å^−3
70 parameters	Δρmin = −0.40 e Å^−3
0 restraints

Special details

Experimental. Prior to data collection, the twinning matrix was determined and it was tested how to achieve separation of reflections stemming from the domains of both domain states.

Refinement. The refinement of the low-temperature data was performed on a data set composed of two merged sets of reflections corresponding to the respective domain states. The exactly superimposed reflections of both domains are 0 k l.

The orientation matrix relating the respective domain states of the low-temperature phase was determined experimentally and corresponds well with an idealized twinning matrix:

$ λeft(µatrix{h_{2} & k_{2} & l_{2} χr}ρight) = λeft (µatrix{h_{1} & k_{1} & l_{1} χr} ρight) πmatrix {−1 & 0 & -(2c/a)χos(βeta) χr 0 & −1 & 0 χr 0 & 0 & 1 χr_$

The respective reflections refer to the first and second domain states. The refinement program JANA2000 (Pet\v r\'_{ι\v cek & Du\v sek, 2000) accounts for the systematic superposition of the reflections that occurs in accordance with the twinning matrix. The refined domain-state fraction resulted in a value of 0.5008 (9). The H atoms were clearly discernible on a difference Fourier map and they were refined as constrained.}

The extinction correction turned out to be insignificant.

From the refinement of the low-temperature phase, 115 unmatched reflections were omitted for which |F_o-F_c| > 3σ(F_o).

The Fourier synthesis was calculated with weighted intensities.

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

	x	y	z	Uiso*/Ueq
Pd	0.5	0.36120 (4)	0.5	0.02878 (14)
N	0.4761 (5)	0.0	0.7475 (3)	0.0302 (15)
C1	0.3295 (6)	0.0	0.6836 (4)	0.0364 (18)
C2	0.4874 (4)	0.0990 (3)	0.8174 (3)	0.0318 (12)
C3	0.1813 (6)	0.0	0.7406 (5)	0.048 (2)
C4	0.4851 (5)	0.2089 (3)	0.7653 (3)	0.0416 (15)
C5	0.6023 (6)	0.0	0.6715 (5)	0.039 (2)
C6	0.7630 (7)	0.0	0.7155 (5)	0.054 (2)
Cl1	0.68149 (15)	0.5	0.50926 (11)	0.0343 (5)
Cl2	0.30818 (13)	0.23448 (9)	0.49324 (9)	0.0413 (4)
H11	0.3297	−0.0605	0.6368	0.0437*
H12	0.5777	0.0931	0.8612	0.0382*
H22	0.4073	0.096	0.8659	0.0382*
H15	0.5887	0.0608	0.6257	0.0467*
H13	0.095	0.0	0.6917	0.0573*
H23	0.1769	−0.0647	0.7832	0.0573*
H16	0.8346	0.0	0.6603	0.0643*
H26	0.7793	0.0647	0.7573	0.0643*
H14	0.4956	0.2661	0.8165	0.0499*
H24	0.5694	0.2133	0.719	0.0499*
H34	0.3888	0.218	0.7269	0.0499*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pd	0.0320 (3)	0.0275 (2)	0.0268 (2)	0.0	0.00138 (17)	0.0
N	0.029 (3)	0.030 (3)	0.031 (3)	0.0	0.0006 (19)	0.0
C1	0.043 (3)	0.032 (3)	0.033 (3)	0.0	−0.012 (3)	0.0
C2	0.032 (2)	0.0321 (19)	0.031 (2)	−0.0002 (16)	−0.0018 (17)	−0.0061 (16)
C3	0.025 (3)	0.051 (4)	0.066 (4)	0.0	−0.010 (3)	0.0
C4	0.049 (3)	0.033 (2)	0.043 (3)	0.001 (2)	0.001 (2)	−0.0040 (18)
C5	0.041 (4)	0.035 (3)	0.042 (3)	0.0	0.011 (3)	0.0
C6	0.045 (4)	0.064 (5)	0.054 (4)	0.0	0.022 (3)	0.0
Cl1	0.0249 (8)	0.0337 (8)	0.0441 (8)	0.0	−0.0021 (7)	0.0
Cl2	0.0399 (7)	0.0336 (6)	0.0505 (7)	−0.0069 (4)	0.0032 (6)	−0.0007 (4)

Geometric parameters (Å, º)

Pd—Cl1	2.3225 (9)	C2—H12	0.960
Pd—Cl1^i	2.3225 (9)	C2—H22	0.960
Pd—Cl2	2.2811 (11)	C3—H13	0.970
Pd—Cl2^ii	2.2811 (11)	C3—H23	0.970
N—C1	1.504 (7)	C3—H23^iii	0.970
N—C2	1.518 (4)	C4—H14	0.970
N—C2^iii	1.518 (4)	C4—H24	0.970
N—C5	1.508 (7)	C4—H34	0.970
C1—C3	1.514 (8)	C5—H15	0.960
C2—C4	1.507 (5)	C5—H15^iii	0.960
C5—C6	1.497 (8)	C6—H16	0.970
C1—H11	0.960	C6—H26	0.970
C1—H11^iii	0.960	C6—H26^iii	0.970
Cl1—Pd—Cl1^i	86.00 (4)	N—C5—C6	116.2 (5)
Cl1—Pd—Cl2	175.72 (4)	H11—C1—H11^iii	100.9
Cl1—Pd—Cl2^ii	89.84 (4)	H11^iii—C1—H11	100.9
Cl1^i—Pd—Cl1	86.00 (4)	H12—C2—H22	101.8
Cl1^i—Pd—Cl2	89.84 (4)	H13—C3—H23	109.5
Cl1^i—Pd—Cl2^ii	175.72 (4)	H13—C3—H23^iii	109.5
Cl2—Pd—Cl2^ii	94.34 (4)	H23—C3—H23^iii	109.5
Cl2^ii—Pd—Cl2	94.34 (4)	H23^iii—C3—H23	109.5
C1—N—C2	111.7 (3)	H14—C4—H24	109.5
C1—N—C2^iii	111.7 (3)	H14—C4—H34	109.5
C1—N—C5	105.1 (4)	H24—C4—H34	109.5
C2—N—C2^iii	105.9 (3)	H15—C5—H15^iii	101.7
C2—N—C5	111.3 (3)	H15^iii—C5—H15	101.7
C2^iii—N—C2	105.9 (3)	H16—C6—H26	109.5
C2^iii—N—C5	111.3 (3)	H16—C6—H26^iii	109.5
N—C1—C3	116.8 (5)	H26—C6—H26^iii	109.5
N—C2—C4	116.2 (3)	H26^iii—C6—H26	109.5

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+1, y, −z+1; (iii) x, −y, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H11···Cl2^iii	0.96	2.84	3.797 (4)	176
C2—H12···Cl1^iv	0.96	2.89	3.806 (4)	161
C2—H12···Cl2^v	0.96	3.35	4.101 (4)	137
C2—H22···Cl1^vi	0.96	3.00	3.915 (4)	159
C2—H22···Cl2^vii	0.96	3.39	4.167 (4)	140
C3—H23···Cl1^vi	0.97	3.06	3.510 (7)	110
C4—H24···Cl2^ii	0.97	3.02	3.895 (4)	152
C4—H34···Cl2	0.97	3.12	3.838 (4)	133
C5—H15···Cl2^ii	0.96	2.80	3.686 (4)	154
C6—H26···Cl1^iv	0.97	3.16	3.612 (7)	110

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