The location of <i>p</i>-dichlorobenzene in a single crystal of zeolite H-ZSM-5 at high sorbate loading

Abstract

The crystal structure of a high-loaded complex of H-ZSM-5 with eight molecules of p -dichlorobenzene per unit cell has been solved by single-crystal X-ray diffraction. The orthorhombic space group P 2 1 2 1 2 1 with a = 20.102 (6), b = 19.797 (9), c = 13.436 (3) Å and V = 5347 (3) Å 3 has four Si 23.92 Al 0.08 O 48 .2C 6 H 4 Cl 2 units per unit cell. D x = 2.164 Mg m −3 , λ (Mo K α) = 0.71073 Å and μ (Mo K α) = 0.876 mm −1 . The final R ( wR ) = 0.046 (0.039), w = 1/ σ 2 ( F ), for 6090 observed reflections with I &gt; 1.0 σ ( I ) measured at 293 K. The straight channel parallel to [010] is slightly corrugated. The elliptical cross sections have limiting apertures of 6.0 × 4.9 Å ( r oxygen = 1.35 Å). The sinusoidal channel parallel to [100] is elliptical with major and minor axes of 6.1 × 4.8 Å, respectively. One of the two independent p -dichlorobenzene molecule lies at the intersection of the straight and sinusoidal channels with its long molecular axis almost parallel to (100) and deviating ~8° from [010]. The second p -dichlorobenzene molecule is in the sinusoidal channel. Its long molecular axis deviates almost 7° from [100] and is practically parallel to (010). The structural aspects are in all details comparable to those in the high-loaded H-ZSM-5/ p -xylene complex [van Koningsveld, Tuinstra, van Bekkum &amp; Jansen (1989). Acta Cryst. B 45 , 423–431] , except for the main interaction forces between the p -dichlorobenzene molecules at the channel intersection.