5-germaspiro[4.4]nona-2,7-dienes

A novel series of bicyclic organogermanium derivatives: 5-germaspiro[4.4]nona-2,7-dienes have been prepared by reaction of 1,1-dihalogermacyclopent-3-enes with the appropriate conjugated diene and an alkali metal in a suitable organic solvent. The best results were obtained by using 1,1-dichlorogermacyclopentenes with isoprene or 2,3-dimethylbutadiene and lithium in 5/1 ether/tetrahydrofuran. Except for 2,3,7,8-tetramethyl-5-germaspiro[4.4]nona-2,7-diene, which is crystalline, the 5-germaspirononadienes are colourless liquids, which distil without decomposition under reduced pressure but which slowly polymerize on standing. In the mass spectra of all the spiradienes, the main peak corresponds to the loss of one ring, the less substituted in the case of unsymmetrical molecules. Attempts to obtain 5-germaspiro[4.4]nona-2,7-diene were unsuccessful.