catena-Poly[[chlorido[1-(3-nitrophenyl)-2-(triphenylphosphoranylidene)ethanone-κC 2]mercury(II)]-μ-chlorido]

In the title organometallic polymer, [HgCl2(C26H20NO3P)]n, the monodentate 1-(3-nitrophenyl)-2-(triphenylphosphoranylidene)ethanone ligand is coordinated to the HgII atom through the methine C atom. The HgII atom is four-coordinated in a distorted tetrahedral geometry by one terminal Cl atom, two bridging Cl atoms, and one C atom from the ylidic ligand, resulting in a polymeric chain parallel to [010]. The terminal Cl atom is more strongly bound to the HgII ion [2.3916 (9) Å] than the bridging Cl atoms. The bridge is asymmetric, as indicated by the two different Hg—Cl(bridging) bond lengths [2.5840 (8) and 2.7876 (8) Å]. Intramolecular C—H⋯O and weak C—H⋯Cl contacts stabilize the polymeric chain. In the crystal, adjacent chains interact via C—H⋯O hydrogen bonds.

In the title organometallic polymer, [HgCl 2 (C 26 H 20 NO 3 P)] n , the monodentate 1-(3-nitrophenyl)-2-(triphenylphosphoranylidene)ethanone ligand is coordinated to the Hg II atom through the methine C atom. The Hg II atom is fourcoordinated in a distorted tetrahedral geometry by one terminal Cl atom, two bridging Cl atoms, and one C atom from the ylidic ligand, resulting in a polymeric chain parallel to [010]. The terminal Cl atom is more strongly bound to the Hg II ion [2.3916 (9) Å ] than the bridging Cl atoms. The bridge is asymmetric, as indicated by the two different Hg-Cl(bridging) bond lengths [2.5840 (8) and 2.7876 (8) Å ]. Intramolecular C-HÁ Á ÁO and weak C-HÁ Á ÁCl contacts stabilize the polymeric chain. In the crystal, adjacent chains interact via C-HÁ Á ÁO hydrogen bonds.

Experimental
Crystal data [HgCl 2 (C 26 H 20 Table 1 Hydrogen-bond geometry (Å , ). Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL. The coordination chemistry of ambidentate ligands (L) has been investigated. The preparation and characterization of stabilized phosphorus ylides, and metal complexes incorporating this type of ylides, has attracted much attention in recent years (Ebrahim et al., 2007). Although many bonding modes are possible for keto-ylides, coordination through ylides methine carbon is more predominant and observed with soft metal ions, e.g. Pd(II), Pt(II), Hg II and Au(I), whereas Ocoordination dominates when the metals involved are hard, e.g. Ti(IV), Zr(IV), and Hf(IV). The crystal and molecular structure of the title complex reveals a polymeric structure, with Hg II ions linked by bridging chlorine, participating in a very asymmetric linear bridge. The asymmetric ligand plays an important role in the building of this unusual supramolecular structure. The building unit ( Fig. 1) is repeated in the polymeric crystal structure. The polymeric structure (part of the chain) and packing diagram for the complex are shown in Fig. 2 and Fig. 3, respectively. The X-ray analysis reveals the coordination of the ylide ligand through the methine C atom only. The Hg II atom is located in a distorted tetrahedral environment, with one terminal Cland two bridging Clions, and one C atom from the ligand, resulting in a one-dimensional polymeric chain. The bond angles around Hg II ion indicate a severe distortion from ideal tetrahedral geometry. The Hg-Cl(terminal) bond length, 2.3916 (9) Å, is shorter than Hg-Cl(bridging) distances. The asymmetric bridging nature of the two chloro ligands is reflected in the unequal Hg-Cl distances of 2.5840 (8) and 2.7876 (8) Å.

Experimental
All reagents and solvents employed were commercially available and were used as received without further purification.

Refinement
H atoms were positioned geometrically with C-H = 0.93 Å (aromatic) or 0.98 Å (methine) and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (carrier C).

Figure 1
The building unit of the title complex [HgCl 2 (L)] n . All H atoms have been omitted for clarity. Displacement ellipsoids are drawn at the 50% probability level.   A packing diagram for the title compounds, with chains running parallel to the b axis. All H atoms have been omitted for clarity.

Figure 4
Resonance forms of the phosphorus ylide(ligand) and its coordination with mercury ion.