Isostructural or not? Adducts of some aryltin halides with (E)-1,2-bis(4-pyridyl)ethene

The title complexes [mu-(E)-4,4'-(ethene-1,2-diyl)dipyridine-kappa(2)N:N']bis[halotris(4-methylphenyl)tin(IV)], [Sn(2)(C(7)H(7))(6)X(2)(C(12)H(10)N(2))], where halo is chloro (X = Cl) and bromo (X = Br) are isostructural. In both crystals, the molecules lie on inversion centers, and there are voids of ca 80 A(3) that could, but apparently do not, accommodate water molecules. The corresponding iodo structure (X = I) is almost, but not quite, isostructural with the other two compounds; when Br is changed to I, the length of the c axis decreases by more than 1 A and the voids are no longer large enough to accomodate any solvent molecule. The related complex [mu-(E)-4,4'-(ethene-1,2-diyl)dipyridine-kappa(2)N:N']bis[chlorotriphenyltin(IV)], [Sn(2)(C(6)H(5))(6)Cl(2)(C(12)H(10)N(2))], crystallizes in a related structure, but the molecules lie on general rather than on special positions. The molecular structures of the four complexes are similar, but the conformation of the phenyl derivative is approximately eclipsed rather than staggered.