Reduction of the org
anodit
ant
alum
allene complex (
ages/gifch
ars/et
a.gif" BORDER=0 >-C
5Me
4R)
2T
a2(
ages/entities/mgr.gif">-X)X
3(
ages/entities/mgr.gif">-
ages/gifch
ars/et
a.gif" BORDER=0 >
1,
ages/gifch
ars/et
a.gif" BORDER=0 >
3-C
3H
4) (R = Me (Cp*), Et; X = Cl, Br) with sodium
am
alg
am le
ads to the propynylidene complex (
ages/gifch
ars/et
a.gif" BORDER=0 >-C
5Me
4R)
2T
a2(
ages/entities/mgr.gif">-H)
2X
2(
ages/entities/mgr.gif">-HCCCH) by
a form
al double 1,3-C-H
activ
ation of the
allene lig
and. The solid-st
ate molecul
ar structure cont
ains
a pl
an
ar HCCCH lig
and bridging, in p
ar
allel coordin
ation mode, the two t
ant
alum
atoms, with the HCCCH
and T
a atoms copl
an
ar. Key structur
al fe
atures
are
a T
a-T
a dist
ance of 2.8817(7) Å, propynylidene C-C-C
angle of 153.7(13)
ages/entities/deg.gif">, C-C dist
ance of 1.370(8) Å, T
a-C(centr
al) dist
ance of 2.194(9) Å,
and T
a-C(termin
al) dist
ance of 1.970(9) Å. Molecul
ar orbit
al c
alcul
ations on the complex
at the RHF/SBK(d)
and B3LYP/L
anL2dz levels of theory demonstr
ate th
at the propynylidene lig
and is best viewed form
ally
as
an
allenediylidene(4-) lig
and bonded to two d
0 t
ant
alum
atoms vi
a two T
a=C(termin
al) double bonds
and
an unusu
al three-center, two-electron bridge bond involving both t
ant
alum
atoms
and
a lone p
air on the pl
an
ar, tetr
acoordin
ate centr
al c
arbon. There is no net T
a-T
a bonding b
ased on the orbit
al
an
alysis.