_P.-Powell-auth.-Principles-of-Organometallic-Chemistry-Springer-Netherlands-1988

The first three periodic groups
ROH/
;-EtH
Et 4 Pb+Pb
Fig. 3.19 Some reactions oftriethylaluminium.* Side reactions when R has .8-hydrogen
e.g. ethyl.
e.g. Et,Al + Et 2 CO --> Et 2 AIOCEt, -+Et,COH addition 55%
~ Et 2 AIOCHEt 2 + C 2 H 4 -+Et 2 CHOH reduction 26%
Et 2 AIOCEt=CHMe + C 2 H 6 -+Et 2 CO enolization 19%
The aluminiumalkyl-catalysed dimerization of propene, followed by thermal
elimination of methane, provides an industrial route to isoprene, which itself is
subsequently, polymerized by a transition metal aluminium alkyl catalyst:
cracking
H,CCH 2CH 2C(CH,)=CH 2 ----->H 2 C=CHC(CH,)=CH 2 + CH 4
Polymerization of alkenes by Ziegler-N atta catalysts is discussed in Chapter 12.
3.9.2 The alkyls as Lewis acids
Towards amines, the acceptor strengths of the Group III methyls Me 3 M,
measured by the enthalpies of dissociation ofthe adducts, lie in the order M =Al
> Ga >In> B > Tl (Table 3.11 ). Apart from Me 3 TI possibly, for which there are
few data, the trimethyls behave as hard acids, preferring nitrogen to phosphorus
donors and oxygen to sulphur donors. In general the order of basicities seems to
be Me 3 N > Me 3 P > Me 3 As > Me 3 Sb > Me 3 Bi and Me 2 0 > Me 2 S > Me 2 Se
-Me 2 Te.
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