A new strained germacycle,
3,4-benzo-1,1,2,2-tetraethyl-1,2-digermacyclobut-3-ene (1),
was
prepared by treatment of 1,2-bis(chlorodiethylgermyl)benzene
with sodium in toluene. At
ambient temperature, 1 was gradually oxidized in air to give
3,4-benzo-1,3-digerma-2-oxacyclopent-4-ene (2), and in the presence of sulfur,
1 was converted to 3,4-benzo-1,3-digerma-2-thiacyclopent-4-ene (3), quantitatively under
similar thermal conditions. The
digermacyclobutene 1 was thermally labile and readily
underwent ring-opening polymerization in toluene to give the corresponding polymer 4
(M
n = 4.4 × 105,
M
w = 7.4 × 105,
M
w/M
n = 1.7). On
thermolysis at 160 °C for 20 h, 1 gave two products,
4,5-benzo-1,2,3-trigermacyclopent-4-ene (5) and
3,4:6,7-dibenzo-1,2,5-trigermacyclohepta-3,6-diene (6),
in
reasonable yields. On the other hand, the thermolysis of
1 in the presence of phenylacetylene
gave 2,3-benzo-1,4-digerma-5-phenyl-cyclohexa-2,5-diene (7),
quantitatively. Further, 1 was
thermolyzed in CCl4 to give two chlorinated products,
1,2-bis(chlorodiethylgermyl)benzene
(9) and
1-(chlorodiethylgermyl)-2-(diethyl(trichloromethyl)germyl)benzene
(10), in reasonable
yields. The reaction mechanisms for the polymerization and the
thermolysis are discussed.
