SCHEDULED MAINTENANCE
Synthesis and crystal structure of dimeric dialkylaluminium µ-dialkylamido compounds
Abstract
Dialkylaluminium µ-dialkylamido compounds of formula
(R
1
2
AlNR
2
2
)
2
(R
1
= Me, Et, Pr
i
, Bu
i
or
Bu
t
; R
2
= Me, Et, Pr
i
,
Bu
i
or Ph) were synthesized by alkane or arene elimination
from the corresponding adduct of formula
R
1
3
Al·NHR
2
2
. The
crystal structures of the following dimeric compounds were determined:
(Me
2
AlNEt
2
)
2
,
(Me
2
AlNBu
i
2
)
2
,
(Et
2
AlNPr
i
2
)
2
,
(Pr
i
2
AlNMe
2
)
2
,
(Pr
i
2
AlNEt
2
)
2
,
(Bu
i
2
AlNMe
2
)
2
,
(Bu
i
2
AlNEt
2
)
2
and also the
mononuclear compound Et
2
Al(OEt
2
)NPh
2
.
The general trends identified in these structures suggest that the
environments around aluminium and nitrogen are affected primarily by
their closest alkyl groups, i.e. R
1
and
R
2
respectively, but that loss of a centre of symmetry is
dependent only on R
2
. Infrared data can also show the
presence of a molecular centre of symmetry. Mass spectroscopic data
suggest that dimers are present in the gas phase but they are partially
dissociated into monomers which in turn fragment into the more stable
species [R
1
AlNR
2
2
]
+
. The NMR
data show that aromatic solvents shield the R
2
protons
causing downfield chemical shifts. Low-pressure (10
-2
Torr) thermal decomposition (500–600 °C) to produce
films of aluminium nitride was studied.
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