catena-Poly[(μ3-2-hydroxy-4-isopropylcyclohepta-2,4,6-trien-1-onato)(μ2-2-hydroxy-4-isopropylcyclohepta-2,4,6-trien-1-onato)lead(II)]

In the title compound, [Pb(C10H11O2)2]n or [Pb(hino)2]n, the lead(II) ion is chelated by two hinokitiolate ligands in a distorted square-pyramidal configuration, with Pb—O bond lengths in the range 2.327 (6)–2.479 (9) Å. The 6s 2 lone electron pair of the lead(II) ion becomes stereochemically active and is directed towards the apex of this pyramid. The crystal structure of the title compound consists of chains formed by the bis(hinokitiolato)lead(II) molecules situated along the twofold screw axis. The coordination sphere around the lead(II) ion is completed by three additional O atoms, at 2.625 (7), 3.016 (8) and 3.064 (8) Å, from the two neighbouring Pb(hino)2 units. Both isopropyl groups are rotationally disordered.

In the title compound, [Pb(C 10 H 11 O 2 ) 2 ] n or [Pb(hino) 2 ] n , the lead(II) ion is chelated by two hinokitiolate ligands in a distorted square-pyramidal configuration, with Pb-O bond lengths in the range 2.327 (6)-2.479 (9) Å . The 6s 2 lone electron pair of the lead(II) ion becomes stereochemically active and is directed towards the apex of this pyramid. The crystal structure of the title compound consists of chains formed by the bis(hinokitiolato)lead(II) molecules situated along the twofold screw axis. The coordination sphere around the lead(II) ion is completed by three additional O atoms, at 2.625 (7), 3.016 (8) and 3.064 (8) Å , from the two neighbouring Pb(hino) 2 units. Both isopropyl groups are rotationally disordered.
The aim of this work was to determine the structure of the homoleptic complex formed by the lead(II) cation and hinokitiolate anions.
The crystal structure of the studied compound consists of chains parallel to the c axis, formed by the Pb(hino) 2 molecules situated around the twofold screw axis. The coordination sphere of the lead(II) ion can be completed by three additional bridging oxygen atoms from the adjacent ligands of two neighbouring Pb(hino) 2 molecules (Fig. 2). These three Pb···O contacts, one rather short, 2.625 (7), and two more distant, 3.016 (8) and 3.064 (8) Å, are much longer than the Pb-O bonds in the chelate, but shorter than the sum of van der Waals radii of lead and oxygen (3.44 Å; Bondi, 1964), which points out to weak interactions. The additional Pb···O distances in the Pb(hino) 2 structure lead to a formal increase of the coordination number of the lead(II) ion from four to seven. supplementary materials sup-2 A similar crystal structure with a bit longer additional Pb···O contacts at 3.013 (5), 3.159 (6) and 3.264 (6) Å was found for bis(acetylacetonato)lead(II), Pb(acac) 2 (Lyczko et al., 2006). The crystal packing in the title compound significantly differs from that obtained for bis(tropolonato)lead(II) complex (Lyczko et al., 2007), in which the [Pb(trop) 2 ] 2 dimeric units can be observed. Nevertheless the main structural feature, which is the distorted square pyramid, looks very similar in all lead(II) α-or β-diketonates discussed above.

Refinement
H atoms were placed in calculated positions with C-H = 0.96 (methyl), 0.98 (methine) or 0.93 Å (aromatic) and were refined isotropic using a riding model with U iso (H) = 1.5 U eq (C) for methyl H atoms and U iso (H) = 1.2 U eq (C) for the rest H atoms. The structure of studied complex fits very well to the collected data. However, the absolute structure could not be determined because Friedel pairs were not measured and in fact the obtained Flack parameter has no physical sense.
The structure was treated with two independent rotational disorders originating from two different isopropyl groups. For the first C 3 H 7 group two-site disorder model consisting of two sets of atoms: C9A, C10A and C9B, C10B with site occupancy factors of 0.69 (4) and 0.31 (4), respectively was refined. The similar model containing C19A, C20A and C19B, C20B atoms with sof of 0.60 (6) and 0.40 (6), respectively was found for the second C 3 H 7 group. C8 and C18 are shared atoms for both components of the disorder in the respective isopropyl groups. Rigid bonds and equal ADPs restraints in the isopropyl parts were employed in the refinement process. Fig. 1. Molecular structure of the title compound with disordered methyl C atoms of isopropyl groups. Displacement ellipsoids of the non-hydrogen atoms are drawn at the 30% probability level.