Crystal structure of a carbon monoxide sorption complex of dehydrated fully manganese(II)-exchanged zeolite X

The crystal structure of a carbon monoxide sorption complex of vacuum-dehyd rated Mn2+-exchanged zeolite X, Mn46Si100Al92O384. 30CO (a=24.715(8) Angstr om) has been determined by single-crystal X-ray diffraction techniques in t he cubic space group Fd (3) over bar at 21(1)degrees C. The complex was pre pared by dehydration at 380 degrees C and 2 x 10(-6) Torr for 3 days, follo wed by exposure at 21(1)degrees C to 270 Torr of carbon monoxide gas. The s tructure was determined in this atmosphere and was refined to the final err or indices, R-1=0.055 and R-2=0.049 with 321 reflections for which I>3 sigm a(I). Mn2+ ions are located at two different sites of high occupancy: 16 Mn 2+ ions fill site I at the centers of the double six-rings, and the remaini ng 30 Mn2+ ions nearly fill site II in the supercage. Each of these latter Mn2+ ions is recessed 0.30 Angstrom into the supercage from the plane of th e three oxygens to which it is bound and coordinates linearly via C to a CO molecule [C-O=0.96(3) A] deeper in the supercage. Each site-II Mn2+ ion is four-coordinate, to three framework oxygens and to one molecule of CO [Mn- C=2.57(3) Angstrom, Mn-O=2.130(9) Angstrom, O-Mn-O=118.1(5)degrees and O-Mn -C=98.0(3)degrees]. The Mn-C bond length is somewhat long, indicative of a relatively weak Mn-CO electrostatic interaction. (C) 1998 Elsevier Science B.V. All rights reserved.