Crystal structure of [5-bromo-2-(pyridin-2-yl-κN)phenyl-κC 1](pentane-2,4-dionato-κ 2 O,O′)platinum(II)

In the title complex, [Pt(C11H7BrN)(C5H7O2)], two crystallographically non-equivalent dimers stacked by π–π interactions are arranged antiparallel to each other.


Chemical context
Square-planar cyclometalated platinum(II) complexes with luminescent properties have recently attracted attention because of their potential applications (Chi & Chou, 2010;Ma et al., 2013), such as DNA probing, as chemical sensors or as organic light-emitting diodes (OLEDs). In particular, platinum(II) complexes including -diketonate anions (e.g. acetylacetonate) as an ancillary ligand have been widely studied because of their excellent stabilities and high quantum yields. Although these complexes afford luminescence in the solid state, their crystal structures have not been sufficiently explored. We report herein the crystal structure of the cyclometalated platinum(II) complex with 2-(4-bromophenyl)pyridinato (Brppy, C 11 H 7 BrN) and acetylacetonato (acac, C 5 H 7 O 2 ) ligands, [Pt(Brppy)(acac)].

Structural commentary
The asymmetric unit of the title compound contains two complex molecules with very similar configurations (r.m.s. deviation of fit of two molecules = 0.07 Å ). The structure of one of the complex molecules of the title compound is shown in Fig. 1. In both complexes, the Pt II atom is coordinated by C ISSN 2056-9890 and N atoms of the bidentate Brppy ligand and two O atoms of the acac ligand. The coordination environments around the central Pt II atoms (Pt1 and Pt2) are slightly distorted from an ideal square-planar configuration, with angles around Pt1 in the range 81.89 (18)-93.04 (17) and around Pt2 in the range 81.73 (18)-93.57 (16) . The Pt-C bond lengths [Pt1-C11 = 1.970 (5) and Pt2-C27 = 1.969 (5) Å ] are slightly shorter than the Pt-N bond lengths [Pt1-N1 = 1.995 (4) and Pt2-N2 = 1.999 (4) Å ] due to the stronger electron-donating ability of a C atom compared to that of an N atom. Pt-O bond lengths are compiled in Table 1. The phenyl and pyridyl rings are approximately coplanar [the dihedral angle between the N1,C1-C5 and C6-C11 rings is 1.31 (17) while that between the N2,C17-C21 and C22-C27 rings is 3.12 (13) ]. In addition, the dihedral angles between two planes composed of the two chelate rings in the cyclometalated complex are 0.08 (12) (involving Pt1) and 1.54 (9) (involving Pt2).

Supramolecular features
As shown in Figs. 2 and 3, in the unit cell two non-equivalent dimers are formed byinteractions between individual complexes. Each non-equivalent dimer is in a head-to-tail form. In each unit cell both types of head-to-tail dimers stacked with an intermolecularinteraction are perpendicular to each other. The -plane of one Pt II complex (Pt1)  Molecular structure of one of the two independent Pt II complexes of the title compound, with displacement ellipsoids drawn at the 50% probability level.  Symmetry codes: (i) Àx þ 1 2 ; Ày þ 1 2 ; Àz þ 1; (ii) x À 1 2 ; Ày þ 1 2 ; z þ 1 2 .

Synthesis and crystallization
The title complex was synthesized according to a traditional two-step preparation method via the dichlorido-bridged dimer complex [Pt(C 11 H 7 BrN)(-Cl)] 2 (Cockburn et al., 1973;Liu et al., 2009), though one-pot synthesis has been reported recently (Hudson et al., 2012).
[Pt(C 11 H 7 BrN)(C 5 H 7 O 2 )]: A mixture of the dichloridobridged dimer complex (0.185 g, 0.20 mmol), acetylacetone (0.020 g, 0.20 mmol) and Na 2 CO 3 (0.211 g, 2.0 mmol) in 2-ethoxyethanol was stirred for 7 h at 323 K under an Ar atmosphere. After cooling to room temperature, the yellow precipitate was filtered off and dried in vacuo. Yield: 0.200 g (47.6%) Yellow single crystals suitable for X-ray structural analysis were grown by vapor diffusion of hexane into the dichloromethane solution of the title complex.
Analysis found (

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. All H atoms were placed in geometrically idealized positions and refined using a riding model, with C-H = 0.95 Å , U iso (H) = 1.2U eq (C) for Csp 2 -H, and U iso (H) = 1.5U eq (C) for methyl H atoms.