Organic metal-complexes. XXI [1]: Synthesis and structure of 3,5,15,17-tetraoxo-1,7,10,13,19,22-hexaoxacyclotetracosane and 2,12,14,24-tetraoxo-4,7,10,16,19,22-hexaoxa-25-mercurato-bicyclo[11.11.1] pentacosane

Article abstract of DOI:10.1002/prac.19983400207

A new synthesis of the title crown via isoxazolo crown ether 7 and macrocyclic bis-β-eneaminoketone 10 is described. 7 can be synthesized in 14% yield by a non-template double-[3+2] cycloaddition of dinitrileoxide 5 prepared in situ from dinitropolyether 19 by dehydration with Ph-NCO and alkyne 6. The compounds 16, 17 and 18 are synthesized by the same synthetic strategy. Comparable IR and ¹H NMR spectroscopic data of macrocyclic and non-cyclic compounds show, that macrocyclic conformation stabilizing effects can be ruled out. The structures of the macrocycles 1, 7, 10 and that of the Hg(II)-complex25, synthesized by reaction of 1 with Hg(OAc)₂ were established by single-crystal X-ray structure analyses. Both inter- and intramolecular hydrogen bonds are observed for the macrocyclic bis-β-eneaminoketone 10, whereas only intramolecular hydrogen bonds are formed by 1. In the Hg(II)-complex of 1 the mercury is bonded to two methylene groups. C-Hg-C is almost linear [177(1)°], the mean Hg-C distance amounts to 215(1) pm. In addition to the Hg-C bonds, each Hg makes a short contact to a carbonyl oxygen in a neighbouring molecule in the plane perpendicular to the C-Hg-C axis [Hg(1)-O(1)=279(1) pm, Hg(2)-O(5)= 284(1) pm]. Johann Ambrosius Barth 1998.