A short survey of bicyclic diamines-syntheses and properties of N,N '-bridged-1,10-diazabicyclooctadeca-5,14-diynes

The conformations and properties of 1,(k + 2)-diazabicyclo[k.l.m]alkanes ar e reviewed briefly. In these species the alkane chains allow inside protona tion but no metal complexation. Inside metal complexation is made possible if the alkane chains incorporate alkyne units. The preparation and structur es of bridged 1,10-diazacyclooctadeca-5,14-diynes are reported. As bridges we use simple alkyl chains from (CH2)(2) to (CH2)(10), di- and triethyleneg lycol, but-2-yne, hex-3-yne, and oct-4-yne chains. The resulting bicyclic s ystems, 34-47, adopt in the solid state either the in/in or the out/out con formations. By means of dynamic NMR spectroscopy a homeomorphic isomerism i n 34 was uncovered. A second dynamic process, a "wagging" motion of the alk yne bridges, could be studied in case of 35. The molecular dimensions in th e solid state reveal N ... N distances between 3.16 Angstrom and 6.52 Angst rom. The intramolecular distances between the triple bonds vary between 4.2 5 Angstrom and 7.31 Angstrom.