trans-Dichloridobis[(pyridin-4-yl)boronic acid-κN]palladium(II) dimethyl sulfoxide disolvate

In the title compound, [PdCl2(C5H6BNO2)2]·2C2H6OS, the PdII ion is located on an inversion centre and is four-coordinated in a trans square-planar geometry by two chloride ions and two (pyridin-4-yl)boronic acid ligands. The Pd—N and Pd—Cl distances are 2.023 (2) and 2.2977 (7) Å, respectively, and the average N—Pd—Cl angle is 90°. The dimethyl sulfoxide solvent molecules play a key role in the crystal structure by bridging the complex molecules via O—H⋯O hydrogen bonds, forming tapes running along the b axis. C—H⋯O interactions also contribute to the cohesion of the crystal.

In the title compound, [PdCl 2 (C 5 H 6 BNO 2 ) 2 ]Á2C 2 H 6 OS, the Pd II ion is located on an inversion centre and is fourcoordinated in a trans square-planar geometry by two chloride ions and two (pyridin-4-yl)boronic acid ligands. The Pd-N and Pd-Cl distances are 2.023 (2) and 2.2977 (7) Å , respectively, and the average N-Pd-Cl angle is 90 . The dimethyl sulfoxide solvent molecules play a key role in the crystal structure by bridging the complex molecules via O-HÁ Á ÁO hydrogen bonds, forming tapes running along the b axis. C-HÁ Á ÁO interactions also contribute to the cohesion of the crystal.

Comment
The title compound was isolated as an air-stable yellow-orange solid. Each Pd II centre lies on a crystallographic inversion centre in a square-planar environment. The chloride and (pyridin-4-yl)boronic acid ligands adopt a trans arrangement due to the molecular symmetry C i ; N-Pd-Cl angles are about 90° (Fig. 1). The bond lengths expected for Pd-N and Pd-Cl (2.023 (2) Å and 2.2977 (7) Å, respectively) are similar to those observed in trans-dichloridobis(pyridine)Pd II (Viossat et al., 1993).
In the crystal structure, the solvent molecules of DMSO are linked by the boronic acid group of the complexes via O-H···O hydrogen bonds (average distance 2.747 (3) Å) to form tapes (Fig. 2, Table 2). The tapes are further connected to create layers by C-H···π interactions (distance C11-H11···Cg1 = 3.815 (4) Å where Cg1 is the centroid of the pyridine ring). Cohesion of the crystals also arises in part from C-H···O interactions involving one methyl moiety of DMSO molecules and oxygen atoms of the boronic acid unit (average C···O distance 3.439 (4) Å).

Experimental
A suspension of PdCl 2 (36 mg, 0.20 mmol) and (pyridin-4-yl)boronic acid (50 mg, 0.41 mmol) in MeCN (20 mL) was stirred for 16 h. The resulting mixture was filtered, and the solid was washed thoroughly with MeCN and then dried under vacuum before being purified by crystallization. Crystals of the title complex were grown by slow evaporation from a solution of the solid in DMSO.

Refinement
All H-atoms were placed in calculated positions (C-H 0.95 -0.98 Å) and were included in the refinement in the riding model approximation with U(H) set to 1.2Ueq (C) for aromatic H and 1.5Ueq (C) for methylene H. Hydroxyl H atoms were first located after a difference Fourier map calculation then refined in the riding model approximation using the AFIX 81 instruction from the SHELX program suite (Sheldrick, 2008), with O-H 0.84 Å and U(H) set to 1.2Ueq(O). Fig. 1. The molecular structure of the title compound with atom labels and 50% probability displacement ellipsoids for non-hydrogen atoms. Hydrogen atoms are drawn as a sphere of arbitrary radius. The unlabelled part is related by the symmetry operation -x, -y, 2 -z.

Special details
Experimental. X-ray crystallographic data for I were collected from a single-crystal sample, which was mounted on a loop fiber. Data were collected using a Bruker Platform diffractometer, equipped with a Bruker SMART 4 K Charged-Coupled Device (CCD) Area Detector using the program APEX2 and a Nonius FR591 rotating anode equiped with Montel 200 optics The crystal-to-detector distance was 5.0 cm, and the data collection was carried out in 512 x 512 pixel mode. The initial unit-cell parameters were determined by a least-squares fit of the angular setting of strong reflections, collected by a 10.0 degree scan in 33 frames over four different parts of the reciprocal space (132 frames total). One complete sphere of data was collected to better than 0.80 Å resolution.
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) were estimated using the full covariance matrix.