3,3-Dimethylselenatane,
S
![[upper bond 1 start]](https://www.rsc.org/images/entities/char_e010.gif)
eCH
2
CMe
2
C
![[upper bond 1 end]](https://www.rsc.org/images/entities/char_e011.gif)
H
2
, DMSe is
cyclooligomerized catalytically at 115 °C in the presence of
[Re
2
(CO)
9
(S
![[upper bond 1 start]](https://www.rsc.org/images/entities/char_e010.gif)
eCH
2
CMe
2
C
![[upper bond 1 end]](https://www.rsc.org/images/entities/char_e011.gif)
H
2
)] to yield three new polyselenoether macrocycles
3,3,7,7-tetramethyl-1,5-diselenacyclooctane,
3,3,7,7,11,11-hexamethyl-1,5,9-triselenacyclododecane,
3,3,7,7,11,11,15,15-octamethyl-1,5,9,13-tetra- selenacyclohexadecane and
polymer of DMSe; all three macrocycles are characterized
crystallographically; in all cases the gem-dimethyl groups are
directed toward the exterior of the rings; interestingly, some methylene
groups are directed to the interior.