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Volume 68 
Part 8 
Pages m223-m225  
August 2012  

Received 11 June 2012
Accepted 5 July 2012
Online 19 July 2012

Pseudosymmetry in a cyclopalladated compound

aInstitute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52074 Aachen, Germany
Correspondence e-mail: ullrich.englert@ac.rwth-aachen.de

The enantiomerically pure title complex, [SP-4-4]-(R)-[2-(1-aminoethyl)phenyl-[kappa]2C1,N]chlorido(quinoline-[kappa]N)palladium(II) acetone hemisolvate, [Pd(C8H10N)Cl(C9H7N)]·0.5C3H6O, crystallizes with four molecules of the organopalladium complex and two molecules of acetone in the asymmetric unit. This corresponds to a discrete hydrogen-bonded aggregate and to the content of the unit cell in the space group P1. Pronounced pseudo-inversion symmetry relates pairs of these objects in the asymmetric unit.

Comment

Cope & Friedrich (1968[Cope, A. C. & Friedrich, E. C. (1968). J. Am. Chem. Soc. 90, 909-913.]) discovered a method for cyclopalladation and cycloplatination of tertiary amines. Subsequent research by Lewis et al. (1973[Lewis, J., Cockburn, B. N., Howe, D. V., Keating, T. & Johnson, B. F. G. (1973). J. Chem. Soc. Dalton Trans. pp. 404-410.]), Dunina et al. (1999[Dunina, V. V., Kuzmina, L. G., Kazakova, M. Yu., Gorunova, O. N., Grishin, Y. K. & Kazakova, E. I. (1999). Eur. J. Inorg. Chem. pp. 1029-1039.]), Fuchita & Tsuchiya (1993[Fuchita, Y. & Tsuchiya, H. (1993). Inorg. Chim. Acta, 209, 229-230.]), Fuchita et al. (1995[Fuchita, Y., Tsuchiya, H. & Miyafuji, A. (1995). Inorg. Chim. Acta, 233, 91-96.], 1997[Fuchita, Y., Yoshinaga, K., Ikeda, Y. & Kinoshita-Kawashima, J. (1997). J. Chem. Soc. Dalton Trans. pp. 2495-2499.]), Vicente et al. (1993[Vicente, J., Saura-Llamas, I. & Jones, P. G. (1993). J. Chem. Soc. Dalton Trans. pp. 3619-3624.], 1997[Vicente, J., Saura-Llamas, I., Palin, M. G., Jones, P. G. & R. de Arellano, M. C. (1997). Organometallics, 16, 826-833.]) and Albert et al. (1997[Albert, J., Cadena, J. M. & Granell, J. (1997). Tetrahedron Asymmetry, 8, 991-994.]) indicated that the reaction can be extended to secondary and primary amines.

[Scheme 1]

In previous work by Calmuschi & Englert, all intermediates along the reaction pathway used to synthesize (I)[link] (see Scheme) have been structurally characterized (Calmuschi & Englert, 2002[Calmuschi, B. & Englert, U. (2002). Acta Cryst. C58, m545-m548.]; Calmuschi, Jonas & Englert, 2004[Calmuschi, B., Jonas, A. E. & Englert, U. (2004). Acta Cryst. C60, m320-m323.]). A variety of pyridine derivatives have been used successfully as [sigma]-donor ligands (Calmuschi, Alesi & Englert, 2004[Calmuschi, B., Alesi, M. & Englert, U. (2004). Dalton Trans. pp. 1852-1857.]; Calmuschi & Englert, 2005[Calmuschi, B. & Englert, U. (2005). CrystEngComm, 7, 171-176.]; Calmuschi-Cula et al., 2005[Calmuschi-Cula, B., Kalf, I., Wang, R. & Englert, U. (2005). Organometallics, 24, 5491-5493.], 2006[Calmuschi-Cula, B., Timofte, C. & Englert, U. (2006). Acta Cryst. E62, m2791-m2793.], 2009[Calmuschi-Cula, B., Kalf, I., Timofte, C. & Englert, U. (2009). Acta Cryst. C65, m48-m51.]; Braun et al., 2011[Braun, B., Kalf, I. & Englert, U. (2011). Chem. Commun. pp. 3846-3848.]). In the present case, we intended to introduce the electronically similar ligand quinoline as an approximate steric equivalent to the nucleobase guanine; guanine itself is only sparingly soluble in solvents compatible with the organopalladium starting material.

The title compound crystallizes in the space group P1. The centrosymmetric supergroup can be safely excluded for the following reasons: (i) a single enantiomer of the primary amine was used; (ii) the distribution of the normalized structure factors is characterized by <E2 - 1> = 0.832, a value close to that expected for a noncentrosymmetric structure; (iii) the strong anomalous signal associated with Pd results in a Flack enantiomorph polarity parameter (Flack, 1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]) of 0.02 (4) and confirms the chirality of the enantiomerically pure reagent (R)-di-[mu]-chlorido-bis{[2-(1-aminoethyl)phenyl-[kappa]2C1,N]palladium(II)}. In addition to four independent molecules of the organopalladium complex in an R configuration, the unit cell of the crystal contains two molecules of acetone (Fig. 1[link]). After refinement of the structure model, the pronounced pseudosymmetry is reflected in correlations between anisotropic displacement parameters encountered for atoms related by pseudo-inversion. We note that a search for higher symmetry (Le Page, 1987[Le Page, Y. (1987). J. Appl. Cryst. 20, 264-269.], 1988[Le Page, Y. (1988). J. Appl. Cryst. 21, 983-984.]), as implemented in PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]), as well as a checkCIF alert, suggested transformation to the supergroup which can be ruled out for the reasons given above. A graphical representation of the pseudo-inversion symmetry is provided in Fig. 2[link], in which the obvious exceptions, namely the methyl groups attached to the homochiral centres, have been highlighted. The symmetry-independent complex molecules differ only slightly with respect to coordination distances; they show, however, significant variation with respect to the orientation of the quinoline ligand. In agreement with the observed pseudosymmetry, two pairs of conformationally similar molecules are encountered. Coordination distances and representative torsion angles have been compiled in Table 1[link].

The asymmetric unit of the title compound also represents a discrete hydrogen-bonded aggregate; Fig. 3[link] shows that the acetone molecules terminate this aggregate, in which the molecules associated with Pd2 and Pd4 act as hydrogen-bond donors via their amino group, and those associated with Pd1 and Pd3 act both as donors (NH) and as acceptors (chloride ligands). Classical hydrogen bonds are summarized in Table 2[link]. The H atoms bonded to electronegative partners and not involved in conventional hydrogen bonds, viz. H11A and H31B, interact with the [pi] systems of the closest benzene rings. The contact distances are H11A...centroid(C41-C46) = 2.68 Å and H31B...centroid(C21-C26) = 2.44 Å.

[Figure 1]
Figure 1
Displacement ellipsoid plot for all molecules in the asymmetric unit of (I)[link]; residues are not shown in a common crystallographic direction but have been aligned for better comparison. Ellipsoids have been drawn at the 50% probability level. All H atoms, except for those attached to the chiral centres, have been omitted.
[Figure 2]
Figure 2
The pseudo-inversion in (I)[link]. Methyl substituents breaking the pseudosymmetry have been highlighted and solvent molecules have been omitted.
[Figure 3]
Figure 3
The hydrogen-bonded aggregate in (I)[link]. Classical hydrogen bonds are shown as dashed lines and N-H...[pi] contacts are shown as dotted lines.

Experimental

Compound (I)[link] was prepared according to the method of Vicente et al. (1993[Vicente, J., Saura-Llamas, I. & Jones, P. G. (1993). J. Chem. Soc. Dalton Trans. pp. 3619-3624.]). (R)-Di-[mu]-chlorido-bis{[2-(1-aminoethyl)phenyl-[kappa]2C1,N]palladium(II)} (14.0 mg, 27 µmol) and quinoline (7.2 mg, 55 µmol) were dissolved in methylene chloride (15 ml) and stirred at 300 K for 1 d. The product was dried under high vacuum and recrystallized by slow evaporation from a solution in acetone at room temperature. (I)[link] crystallizes as colourless rods.

Crystal data
  • [Pd(C8H10N)Cl(C9H7N)]·0.5C3H6O

  • Mr = 420.21

  • Triclinic, P 1

  • a = 11.9699 (18) Å

  • b = 12.3754 (19) Å

  • c = 12.4793 (19) Å

  • [alpha] = 104.369 (3)°

  • [beta] = 95.465 (3)°

  • [gamma] = 95.802 (3)°

  • V = 1767.6 (5) Å3

  • Z = 4

  • Mo K[alpha] radiation

  • [mu] = 1.20 mm-1

  • T = 100 K

  • 0.35 × 0.14 × 0.07 mm

Data collection
  • Bruker D8 goniometer with a SMART APEX CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2004[Bruker (2004). SADABS. Bruker AXS Inc., Madison Wisconsin, USA.]) Tmin = 0.455, Tmax = 0.745

  • 21565 measured reflections

  • 14570 independent reflections

  • 11833 reflections with I > 2[sigma](I)

  • Rint = 0.049

Refinement
  • R[F2 > 2[sigma](F2)] = 0.054

  • wR(F2) = 0.116

  • S = 1.01

  • 14570 reflections

  • 585 parameters

  • 3 restraints

  • H-atom parameters constrained

  • [Delta][rho]max = 0.95 e Å-3

  • [Delta][rho]min = -0.77 e Å-3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), 7126 Friedel pairs

  • Flack parameter: 0.02 (4)

Table 1
Selected geometric parameters (Å, °)

Pd1-C11 1.981 (9)
Pd1-N11 2.027 (7)
Pd1-N12 2.055 (7)
Pd1-Cl1 2.418 (2)
Pd2-C21 2.004 (9)
Pd2-N21 2.024 (6)
Pd2-N22 2.038 (7)
Pd2-Cl2 2.417 (2)
Pd3-C31 1.981 (9)
Pd3-N32 2.034 (7)
Pd3-N31 2.053 (7)
Pd3-Cl3 2.394 (2)
Pd4-C41 1.964 (9)
Pd4-N41 2.040 (6)
Pd4-N42 2.055 (7)
Pd4-Cl4 2.429 (2)
Cl1-Pd1-N12-C19 -98.1 (7)
Cl2-Pd2-N22-C29 -86.0 (7)
Cl3-Pd3-N32-C39 100.2 (6)
Cl4-Pd4-N42-C49 85.4 (6)

Table 2
Hydrogen-bond geometry (Å, °)

D-H...A D-H H...A D...A D-H...A
N11-H11B...Cl3 0.92 2.41 3.241 (7) 151
N21-H21A...Cl3 0.92 2.47 3.379 (9) 171
N21-H21B...O6 0.92 2.20 2.983 (10) 143
N31-H31A...Cl1 0.92 2.45 3.301 (7) 154
N41-H41A...O5 0.92 2.18 3.056 (10) 160
N41-H41B...Cl1 0.92 2.40 3.310 (9) 171

After conventional refinement with anisotropic displacement parameters for all non-H atoms, correlations between displacement parameters for atoms related by pseudo-inversion were encountered. Therefore, the anisotropic displacement parameters for all non-H atoms related by pseudo-inversion, i.e. for all non-H atoms except for the chiral centres CX7 (X = 1-4) and the methyl C atoms CX8 attached to them, were constrained to be equal, resulting in a total of 252 equality constraints. For the thus constrained model, an agreement factor of wR2 = 0.1157 for 14570 data and 585 variables was obtained, only marginally higher than for the unconstrained model with wR2 = 0.1136 for the same number of data and 837 variables. H atoms were treated as riding, with N-H = 0.92 Å, C-H = 0.95 Å for CH3, C-H = 0.99 Å for aryl CH and C-H = 1.00 Å for alkyl CH groups. Isotropic displacement parameters were constrained to Uiso(H) = 1.5Ueq(C) for methyl groups or 1.2Ueq(C,N) otherwise. Tentative refinement of the amino H atoms with N-H distance restraints did not result in satisfactory geometries for these groups, most likely due to high correlation.

Data collection: SMART (Bruker, 2001[Bruker (2001). SMART. Bruker AXS Inc., Madison Wisconsin, USA.]); cell refinement: SMART; data reduction: SAINT (Bruker, 1999[Bruker (1999). SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA.]); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]) and Mercury (Macrae et al., 2008[Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466-470.]); software used to prepare material for publication: SHELXL97.


Supplementary data for this paper are available from the IUCr electronic archives (Reference: YF3015 ). Services for accessing these data are described at the back of the journal.


Acknowledgements

We thank our colleague Fangfang Pan for help with the data collection.

References

Albert, J., Cadena, J. M. & Granell, J. (1997). Tetrahedron Asymmetry, 8, 991-994.  [CrossRef] [ChemPort]
Braun, B., Kalf, I. & Englert, U. (2011). Chem. Commun. pp. 3846-3848.  [CSD] [CrossRef]
Bruker (1999). SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA.
Bruker (2001). SMART. Bruker AXS Inc., Madison Wisconsin, USA.
Bruker (2004). SADABS. Bruker AXS Inc., Madison Wisconsin, USA.
Calmuschi, B., Alesi, M. & Englert, U. (2004). Dalton Trans. pp. 1852-1857.  [CSD] [CrossRef]
Calmuschi, B. & Englert, U. (2002). Acta Cryst. C58, m545-m548.  [CSD] [CrossRef] [details]
Calmuschi, B. & Englert, U. (2005). CrystEngComm, 7, 171-176.  [ChemPort]
Calmuschi, B., Jonas, A. E. & Englert, U. (2004). Acta Cryst. C60, m320-m323.  [CrossRef] [details]
Calmuschi-Cula, B., Kalf, I., Timofte, C. & Englert, U. (2009). Acta Cryst. C65, m48-m51.  [CSD] [CrossRef] [details]
Calmuschi-Cula, B., Kalf, I., Wang, R. & Englert, U. (2005). Organometallics, 24, 5491-5493.  [CSD] [CrossRef] [ChemPort]
Calmuschi-Cula, B., Timofte, C. & Englert, U. (2006). Acta Cryst. E62, m2791-m2793.  [CSD] [CrossRef] [details]
Cope, A. C. & Friedrich, E. C. (1968). J. Am. Chem. Soc. 90, 909-913.  [CrossRef] [ChemPort] [ISI]
Dunina, V. V., Kuzmina, L. G., Kazakova, M. Yu., Gorunova, O. N., Grishin, Y. K. & Kazakova, E. I. (1999). Eur. J. Inorg. Chem. pp. 1029-1039.  [CrossRef]
Flack, H. D. (1983). Acta Cryst. A39, 876-881.  [CrossRef] [details]
Fuchita, Y. & Tsuchiya, H. (1993). Inorg. Chim. Acta, 209, 229-230.  [CrossRef] [ChemPort]
Fuchita, Y., Tsuchiya, H. & Miyafuji, A. (1995). Inorg. Chim. Acta, 233, 91-96.  [CrossRef] [ChemPort]
Fuchita, Y., Yoshinaga, K., Ikeda, Y. & Kinoshita-Kawashima, J. (1997). J. Chem. Soc. Dalton Trans. pp. 2495-2499.  [CrossRef]
Le Page, Y. (1987). J. Appl. Cryst. 20, 264-269.  [CrossRef] [details]
Le Page, Y. (1988). J. Appl. Cryst. 21, 983-984.  [CrossRef] [details]
Lewis, J., Cockburn, B. N., Howe, D. V., Keating, T. & Johnson, B. F. G. (1973). J. Chem. Soc. Dalton Trans. pp. 404-410.
Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466-470.  [ISI] [CrossRef] [ChemPort] [details]
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.  [CrossRef] [details]
Spek, A. L. (2009). Acta Cryst. D65, 148-155.  [ISI] [CrossRef] [details]
Vicente, J., Saura-Llamas, I. & Jones, P. G. (1993). J. Chem. Soc. Dalton Trans. pp. 3619-3624.  [CrossRef]
Vicente, J., Saura-Llamas, I., Palin, M. G., Jones, P. G. & R. de Arellano, M. C. (1997). Organometallics, 16, 826-833.


Acta Cryst (2012). C68, m223-m225   [ doi:10.1107/S0108270112030776 ]