Structure of a cyclopropane sorption complex of dehydrated fully Mn 2+-exchanged zeolite X

Abstract

The structure of a cyclopropane sorption complex of dehydrated fully Mn 2+-exchanged zeolite X, Mn 46Si 100Al 92O 384 · 30C 3H 6 ( a=24.690(4) Å), has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd 3 at 21(1)°C. The crystal was prepared by ion exchange in a flowing stream of 0.05 M aqueous Mn(NO 3) 2 for three days, followed by dehydration at 460°C and 2×10 −6 Torr for two days, and exposure to 100 Torr of cyclopropane gas at 21(1)°C. The structure was determined in this atmosphere and was refined to the final error indices R 1=0.065 and R 2=0.071 with 509 reflections for which I>3 σ (I). In this structure, Mn 2+ ions are located at two crystallographic sites. Sixteen Mn 2+ ions fill the octahedral site I at the centers of the hexagonal prisms (Mn–O=2.290(9) Å). The remaining 30 Mn 2+ ions are at site II; each extends 0.41 Å into the supercage (an increase of 0.27 Å upon C 3H 6 sorption as compared to fully dehydrated Mn 46Si 100Al 92O 384) where it coordinates to three trigonally arranged framework oxygens at 2.148(8) Å and complexes weakly and facially to a cyclopropane molecule by a primarily quadrupolar interaction. The carbon atoms of each cyclopropane molecule are equivalent and equidistant from its Mn 2+ ion (Mn–C=2.95(9) Å). Because of high thermal motion, the C–C bond length is inaccurately determined; the value found, 1.21(8) Å, is too small.