Acetylene–ammonia–18-crown-6 (1/2/1)

Abstract

The title compound, C2H2·C12H24O6·2NH3, was formed by co-crystallization of 18-crown-6 and acetyl­ene in liquid ammonia. The 18-crown-6 mol­ecule has threefold rotoinversion symmetry. The acteylene mol­ecule lies on the threefold axis and the whole mol­ecule is generated by an inversion center. The two ammonia mol­ecules are also located on the threefold axis and are related by inversion symmetry. In the crystal, the ammonia mol­ecules are located below and above the crown ether plane and are connected by inter­molecular N—H⋯O hydrogen bonds. The acetyl­ene mol­ecules are additionally linked by weak C—H⋯N inter­actions into chains that propagate in the direction of the crystallographic c axis. The 18-crown-6 mol­ecule [occupancy ratio 0.830 (4):0.170 (4)] is disordered and was refined using a split model.

Polynuclear Hydroxido-Bridged Complexes of Platinum(IV) with Terminal Nitrato Ligands

“…Fragments [H 3 O⊂18-crown-6] + are disordered over two pairs of positions (occupancy 0.3 and 0.2) where every pair consists of two crystallographic positions that differ by the angle of rotation around the axis of 18-crown-6 molecules. Such disorder pattern is not rare for crown ether, , but the presence of heavy metal atoms in the structure makes it complicated to find unambiguous solutions. Therefore, [H 3 O⊂18-crown-6] + molecules were modeled without hydrogen atoms and in an isotropic approximation.…”

Synthesis, Isolation, and Study of Heterobimetallic Uranyl Crown Ether Complexes

“…The average ω crown parameter for 2 is 0.23(3), similar to the value of 0.20(1) found for 1 , suggesting that little reorganization of the ligand is required for uranyl binding. Additionally, the ω crown values of a representative set of structures of bare 18-crown-6 ligands lacking interactions with ions are all larger (spanning from 0.228 to 0.254) than the value for 1 of 0.20(1), suggesting that the accessory Pt(II)-containing site enhances the net planarity of the crown, poising it for uranyl capture. In accord with this theory, the out-of-plane deviations of the nascent bridging phenoxide O atoms are significantly smaller in 1 (0.121 for O1 and 0.216 for O2) than the O-atoms of the bare crowns (spanning from 0.228 to 0.254).…”