6 Group 13–15 Needle-Shaped Oligomers and Nanorods: Structures. . .
207
not accessible by the elimination route. As an example, reactions of [HAlN i Pr] 6
with AlMe 3 and AlEt 3 produce methyl- and ethyl-substituted hexamer species
[MeAlN i Pr] 6 and [EtAlN i Pr] 6 , respectively. In contrast, direct reaction between
AlMe 3 or AlEt 3 and NH 2
i Pr resulted in tetramers [MeAlN i Pr] 4 and [EtAlN i Pr] 4
[85].
HCl, HgCl 2 , and TiCl 4 were used to obtain partially or fully chlorinated poly(Nalkyliminoalanes), starting from the corresponding hydride derivatives [79].
[HAlNR] n + n HCl
Et 2 O
−→ [ClAlNR] n + nH 2
[HAlNR] n +
n / 2 HgCl 2
Et 2 O
−→ [ClAlNR] n +
n / 2 Hg+
n / 2 H 2
[HAlNR] n + n TiCl 4
n−heptane
−→
[ClAlNR] n + n TiCl 3 +
n / 2 H 2
A series of Cl- and Br-substituted compounds was obtained by substitution
from [HAlNCH 2 Ph] 6 [80, 81, 84]. Roesky was able to introduce six ferrocene
units CpFeC 5 H 4 C≡C as substituents to form very bulky hexamer compound
[CpFeC 5 H 4 C≡CAlNCH 2 Ph] 6 [84]. One of the drawbacks of such an approach
is incompleteness of the substitution reaction. Thus, only partial substitution of
H by F atoms was achieved by treating heptamer compound [HAlNCH 2 (1-Ad)] 7
with Me 3 SnF. Resulting product has an empiric formulae [F 0.32 H 0.68 AlNCH 2 (1Ad)] 7 [82]. Reaction of [HAlNR] 4 with ZpCp 2 Me 2 leads to stepwise substitution
of H into Me groups, forming [Me 0.22 H 0.78 AlNR] 4 , [Me 0.5 H 0.5 AlNR] 4 , and finally
[MeAlNR] 4 [83].
Series of substitution reactions have been performed for the [HAlNR] n compounds (n=4,6,8) by Nöth and Wolfgardt, resulting in full or partially substituted compounds X m H n-m [AlNR] n (X=D,Cl,Br,I) [86, 87]. Mechanism of a
hydrogen/deuterium exchange via formation of intermediates with pentacoordinate
aluminum was discussed in work [87].
Despite numerous successful examples, the application of substitution reactions
is limited due to undesired side processes, one of which is a cage degradation to form amido compounds [79]. Cage degradation reaction was observed
upon interaction of PhSH with [HAlNCH 2 (C 4 H 3 S)] 6 , producing amido compound
[(PhS) 2 AlNHCH 2 (C 4 H 3 S)] 2 instead of the desired [PhSAlNCH 2 (C 4 H 3 S)] 6 [81].
Computational studies suggest that both substitution reactions of [HAlNR] n and
cage degradation reactions with formation of amido compounds [H 2 AlNR 2 ] m are
thermodynamically favorable and therefore can proceed concurrently [47].
Polyalkyliminoalanes can be also produced in one-pot reaction between aluminum and primary amines in hydrogen atmosphere [88]:
Al + RNH 2 =
1 / n [HAlNR] n +
1
2
H 2
207
not accessible by the elimination route. As an example, reactions of [HAlN i Pr] 6
with AlMe 3 and AlEt 3 produce methyl- and ethyl-substituted hexamer species
[MeAlN i Pr] 6 and [EtAlN i Pr] 6 , respectively. In contrast, direct reaction between
AlMe 3 or AlEt 3 and NH 2
i Pr resulted in tetramers [MeAlN i Pr] 4 and [EtAlN i Pr] 4
[85].
HCl, HgCl 2 , and TiCl 4 were used to obtain partially or fully chlorinated poly(Nalkyliminoalanes), starting from the corresponding hydride derivatives [79].
[HAlNR] n + n HCl
Et 2 O
−→ [ClAlNR] n + nH 2
[HAlNR] n +
n / 2 HgCl 2
Et 2 O
−→ [ClAlNR] n +
n / 2 Hg+
n / 2 H 2
[HAlNR] n + n TiCl 4
n−heptane
−→
[ClAlNR] n + n TiCl 3 +
n / 2 H 2
A series of Cl- and Br-substituted compounds was obtained by substitution
from [HAlNCH 2 Ph] 6 [80, 81, 84]. Roesky was able to introduce six ferrocene
units CpFeC 5 H 4 C≡C as substituents to form very bulky hexamer compound
[CpFeC 5 H 4 C≡CAlNCH 2 Ph] 6 [84]. One of the drawbacks of such an approach
is incompleteness of the substitution reaction. Thus, only partial substitution of
H by F atoms was achieved by treating heptamer compound [HAlNCH 2 (1-Ad)] 7
with Me 3 SnF. Resulting product has an empiric formulae [F 0.32 H 0.68 AlNCH 2 (1Ad)] 7 [82]. Reaction of [HAlNR] 4 with ZpCp 2 Me 2 leads to stepwise substitution
of H into Me groups, forming [Me 0.22 H 0.78 AlNR] 4 , [Me 0.5 H 0.5 AlNR] 4 , and finally
[MeAlNR] 4 [83].
Series of substitution reactions have been performed for the [HAlNR] n compounds (n=4,6,8) by Nöth and Wolfgardt, resulting in full or partially substituted compounds X m H n-m [AlNR] n (X=D,Cl,Br,I) [86, 87]. Mechanism of a
hydrogen/deuterium exchange via formation of intermediates with pentacoordinate
aluminum was discussed in work [87].
Despite numerous successful examples, the application of substitution reactions
is limited due to undesired side processes, one of which is a cage degradation to form amido compounds [79]. Cage degradation reaction was observed
upon interaction of PhSH with [HAlNCH 2 (C 4 H 3 S)] 6 , producing amido compound
[(PhS) 2 AlNHCH 2 (C 4 H 3 S)] 2 instead of the desired [PhSAlNCH 2 (C 4 H 3 S)] 6 [81].
Computational studies suggest that both substitution reactions of [HAlNR] n and
cage degradation reactions with formation of amido compounds [H 2 AlNR 2 ] m are
thermodynamically favorable and therefore can proceed concurrently [47].
Polyalkyliminoalanes can be also produced in one-pot reaction between aluminum and primary amines in hydrogen atmosphere [88]:
Al + RNH 2 =
1 / n [HAlNR] n +
1
2
H 2