Cyclic Acetylenic Compounds

Annulenes, 1980–2000

“…Dehydroannulenes are in fact of considerable interest in themselves; it had been suggested as long ago as 1948 138 that they should be aromatic compounds provided that they have the correct number of conjugated π-electrons to form a delocalised π-orbital and that the rings were planar. However, the introduction of triple bonds in place of double bonds might have a number of effects on the stability and bond structure of the ring.…”

A Gold(I) [2]Catene

“…after which time the volume \*as concentrated under reduced pressure to give a dark yellow precipitate. This was filtered, dissolved in a minimum volume of hot EtOH and left in a refrigerator at about ing rings make a dihedral angle of 64.5" and interring gold-gold contacts lie in the range between 3.215(2)-3.351 (2) A. leading to a symmetrical [2]catenane structure. The individual rings have approximately C , symmetry as a result of the ethynyl ligand bonding modes described above, and if one ignores the ligands the central Au,, core has approximately D, symmetry.…”

“…The manner in which the basic [Au(C=CtBu)] fragments rearrange their coordination environments in solution and self-assemble in order to realize the observed solid-state structure remains a mystery. IR studies on the [2]catenane in solution have indicated that the three v(C=C) bands observed in the solid are also observed in solution (IR (CCI,): v(C=C) 2003(CCI,): v(C=C) , 1985(CCI,): v(C=C) , 1965 suggesting that the ring structure is maintained in solution. Two 'H resonances for the tBu groups in the ratio of 2: 1 in the 'H NMR spectrum at room temperature (see experimental) are also consistant with the C , symmetry of the individual rings.…”

“…The observation of such an interesting catenane structure based on such simple homoleptic organometallic complex is really most unexpected and novel. Previous examples of [2]catenane complexes have the metal atoms involved in much more complex polyaromatic nitrogen ligand systems[91 and in some cases two different metal ions. [101 We are currently investigating similar compounds in order to establish the extent to which the "aurophilicity" of the gold atoms is contributing to the spontaneous formation of the [2]catenane.…”

Synthesis of New Sworski‐Type Dehydroannulenes: 3,4‐Benz‐1,2,5,6,8,9,12,13‐octadehydro[14]‐annulenes

“…Molecular structure of[2]catenane-[{Au(C&/Bu)),),. For reasons ofclarity the methyl groups have been excluded.…”