The reaction of Al(tBu)3 with ethylene glycol (HOCH2CH2OH) in hexane yields “alucone”
polymers, [Al(tBu)2
x
(OCH2CH2O)1.5
-
x
]
n
(0.3 ≤ 2x ≤ 0.8), with the concurrent formation of
[Al2(tBu)3(OCH2CH2O)(OCH2CH2OH)] (1). If the reaction is carried out in Et2O solution,
then [Al3(tBu)5(OCH2CH2O)2] (2) may be isolated. The molecular structure of compound 1
consists of a dimer formed by the alkoxide termini of two ligands bridging the Al(tBu) and
Al(tBu)2 units. The Al(tBu) moiety is chelated by the nonbridging oxygens of the glycolate
ligands, one of which remains protonated. Compound 2 consists of two Al(tBu)2 units and
two glycolate ligands forming a cryptand-like 10-membered heterocycle; the Al(tBu) unit is
positioned capping the four oxygen atoms. As with the previously reported ethoxy-substituted
alucone polymers, [Al(OR)2
x
(OCH2CH2O)1.5
-
x
]
n
, thermolysis of [Al(tBu)2
x
(OCH2CH2O)1.5
-
x
]
n
,
results in the formation of η-alumina (η-Al2O3) as determined by XRD. This is in contrast to
the formation of γ-Al2O3 from the thermolysis of alumoxanes, [Al(O)(OR)
x
(OH)1
-
x
]
n
, and may
be rationalized by the structural relationship of compounds 1 and 2, and hence the alucones,
to Bayerite rather than the boehmite core observed for alumoxanes.