A new polymorph of poly[bis(μ2-perchlorato-κ2O:O′)(2,2′:6′,2"-terpyridine-κ3N,N′,N")lead(II)] with a greatly extended chain repeat distance

In the title compound, [Pb(ClO4)(2)(C15H11N3)](n), two molecules occupy general positions while the third lies on a crystallographic twofold axis, giving a total of two and a half molecules per asymmetric unit. Each metal centre is coordinated equatorially by three 2,2':6',2''-terpyridine (terpy) N-donor atoms and axially by two perchlorate O-donor atoms. The distorted pentagonal bipyramidal geometry is completed by two equatorial O-donor atoms from two perchlorate anions which bridge to two different adjacent metal centres. The coordination about each metal centre is very similar to that seen at the unique Pb-II centre in the previously published polymorph [Engelhardt, Harrowfield, Miyamae, Patrick, Skelton, Soudi & White (1996). Aust. J. Chem. 49, 1135-1146], but the new polymorph differs from it by the insertion on each side of an existing [bis(perchlorato)(terpy)lead(II)] molecule of two additional such units. Pairs of asymmetrically bridging perchlorate anions link irregularly spaced Pb II centres into undulating chains parallel to [201] which exhibit a repeat distance of 26.280 (4) angstrom. The significance of this new polymorph lies in the fact that, while it is chemically identical to the known polymorph, it is structurally distinct from it.