catena-Poly[[[O,O′-bis(2-methylphenyl) dithiophosphato-κ2 S,S]lead(II)]-μ-O,O′-bis(2-methylphenyl) dithiophosphato-κ3 S,S′:S]

In the title compound, [Pb(C14H14O2PS2)2]n, the metal atom is surrounded by two O,O′-bis(2-methylphenyl) dithiophosphate ligands bonding through the S-donor atoms. Three of the Pb—S bond lengths are are close to each other at 2.7710 (18), 2.8104 (16) and 2.8205 (16) Å, while the fourth Pb—S bond is elongated at 3.0910 (18) Å and reflects the fact that this atom is involved in intermolecular bridging to an adjacent PbII atom [Pb—S = 3.145 (2) Å]. The bond angles demonstrate that the PbII atom contains a stereochemically active lone pair with a distorted octahedral geometry about the PbII atom. This distortion is shown by the S—Pb—S bite angles of 73.63 (4) and 69.50 (4)°, while the remaining S—Pb—S angles range from 81.03 (5) to 143.66 (5)°. One of the benzene rings shows positional disorder over two orientations with occupancy factors of 0.747 (11) and 0.253 (11).

In the title compound, [Pb(C 14 H 14 O 2 PS 2 ) 2 ] n , the metal atom is surrounded by two O,O 0 -bis(2-methylphenyl) dithiophosphate ligands bonding through the S-donor atoms. Three of the Pb-S bond lengths are are close to each other at 2.7710 (18), 2.8104 (16) and 2.8205 (16) Å , while the fourth Pb-S bond is elongated at 3.0910 (18) Å and reflects the fact that this atom is involved in intermolecular bridging to an adjacent Pb II atom [Pb-S = 3.145 (2) Å ]. The bond angles demonstrate that the Pb II atom contains a stereochemically active lone pair with a distorted octahedral geometry about the Pb II atom. This distortion is shown by the S-Pb-S bite angles of 73.63 (4) and 69.50 (4) , while the remaining S-Pb-S angles range from 81.03 (5) to 143.66 (5) . One of the benzene rings shows positional disorder over two orientations with occupancy factors of 0.747 (11) and 0.253 (11).

Experimental
Crystal data [Pb(C 14 (Clark & Reid, 1995)] T min = 0.094, T max = 0.675 10226 measured reflections 4494 independent reflections 4269 reflections with I > 2(I) R int = 0.045 explained in terms of coordination chemistry by the ability of these compounds to perform different structural functions and act as bidentate terminal, bidentate bridging or combined ligands. As a result, compounds with different types of structural organization can be formed: mono-, bi-, tetra-, or polynuclear complexes. A unique alternation of the conformationally different (`chair`-`saddle`) eight-membered rings [Cd 2 S 4 P 2 ] has been revealed in the chains of polynuclear cadmium(II) complexes [Cd{S(S)P(OR) 2 } 2 ] n (Lawton & Kokotailo, 1969;Lawton & Kokotailo, 1972;Ito, 1972;Harrison et al., 1988). General and convenient methods to prepare dithiophosphato salt derivatives have been reported (Van Zyl & Fackler, 2000;Van Zyl, 2010). In view of the importance of these compounds and in continuation of our earlier work (Bajia et al., 2009;Maheshwari et al., 2009) we have undertaken the crystal structure determination of the title compound, and the results are presented here. Pb 2+ complexes of these types of ligands are of particular interest because of the possibility of exhibiting stereochemically active lone pairs (Davidovich et al., 2010;Ito & Maeda, 2004;Larsson et al., 2004;Lawton & Kokotailo, 1972).
The X-ray study confirmed the molecular structure and atomic connectivity for (I), as illustrated in Fig. 1. The structure consists of a linear zigzag chain of molecules in the b direction composed of one Pb atom and two chelating bis(2methylphenyl) phosphato ligands and linked by Pb-S-Pb bonds. The two bis(2-methylphenyl) phosphato ligands are coordinated through both S atoms to the metal. Three of the Pb-S bond lengths are insignificantly different at 2.7710 (18), 2.8104 (16) and 2.8205 (16) Å, while the fourth Pb-S bond is elongated at 3.0910 (18) Å and reflects the fact that this atom is involved in intermolecular bridging (symmetry code, 2 -x,1/2 + y,1 -z) to an adjacent Pb (intermolecular Pb-S distance, 3.145 (2) Å).
The bond angles reflect the fact that Pb contains a stereochemically active lone pair so the geometry about the Pb is best described using VSEPR theory as AX 5 E (Gillespie & Nyholm, 1957) and is thus distorted octahedral. The S-Pb-S bite angles are small at 73.63 (4) and 69.50 (4)° while the remaining S-Pb-S angles range from 81.03 (5) to 143.66 (5)°.
Thus the relative bond distances and angles for the title compound agree with the presence of an electron lone pair in a distorted octahedral PbS 5 E (with one S as a bridging ligand) environment. Evidence for the presence of a stereochemically active electron lone pair of the lead atom has also been reported for other Pb 2+ complexes with similar ligands (Davidovich et al., 2010;Ito & Maeda, 2004;Larsson et al., 2004;Lawton & Kokotailo, 1972).
No evidence for C-H···O or C-H···S interactions were found in the crystal.

Refinement
All H atoms were positioned geometrically and refined as riding atoms, with C-H = 0.93 (CH) and 0.96(CH 3 ) Å and with U iso (H) = 1.2U eq (C). The highest residual electron density was found 0.69 Å from Pb the deepest hole 0.82 Å from Pb.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.