The synthesis, structures, and reactivity of cationic aluminum complexes co
ntaining the N,N ' -diisopropylaminotroponiminate ligand (Pr-i(2)-ATI(-)) a
re described. The reaction Of ( Pr-i(2)-ATI)AIR(2) (1a-e,g,h; R = H (a), Me
(b), Et (c), Pr (d), Bu-i (e), Cy (g), CH2Ph (h)) with (Ph3C][B(C6F5)(4)]
yields (Pr-i(2)-ATI)AlR+ species whose fate depends on the properties of th
e R ligand. la and lb react with 0.5 equiv of [Ph3C][B(C6F5)(4)] to produce
dinuclear monocationic complexes [{(Pr-i(2)-ATI)AlR}(2)(mu -R)][(C6F5)(4)]
(2a,b). The cation of 2b contains two (Pr-i(2)-ATI)AIMe+ units linked by a
n almost linear Al-Me-Al bridge; 2a is presumed to have an analogous struct
ure. 2b does not react further with [Ph3C][B(C6F5)(4)]. However, 1a reacts
with 1 equiv of [Ph3C][B(C6F5)(4)] to afford (Pr-i(2)-ATI)Al(C6F5)(mu -H)(2
)B(C6F5)(2) (3) and other products, presumably via C6F5-transfer and ligand
redistribution of a [(Pr-i(2)-ATI)AlH][(C6F5)(4)] intermediate. 1c-e react
with 1 equiv of [Ph3C][B(C6F5)(4)] to yield stable base-free [(Pr-i(2)-ATI
)AlR][B(C6F5)(4)] complexes (4c-e). 4c crystallizes from chlorobenzene as 4
c(CIPh).0.5PhCl, which has been characterized by X-ray crystallography. In
the solid state the PhCl ligand of 4c(ClPh) is coordinated by a dative PhCl
-Al bond and an ATI/Ph T-stacking interaction. 1g,h react with [Ph3C][B(C6F
5)(4)] to yield (Pr-i(2)-ATI)Al(R)(C6F5) (5c,h) via C6F5- transfer of [(Pr-
i(2)-ATI)AlR][(BC6F5)(4)] intermediates. 1c,h react with B(C6F5)3 to yield
(Pr2-ATI)Al(R)(C6F5) (5c,h) via C6F5- transfer of [(Pr-i(2)-ATI)AlR][RB(C6F
5)(3)] intermediates. The reaction of 4c-e with MeCN or acetone yields [(Pr
-i(2)-ATI)Al(R)(L)][B(C6F5)(4)] adducts (L = MeCN (8c-e), acetone (9c-e)),
which undergo associative intermolecular L exchange. 9c-e undergo slow beta
-H transfer to afford the dinuclear dicationic alkoxide complex [{(i)(Pr(2
)ATI)Al(mu -(OPr)-Pr-i)}(2)][B(C6F5)(4)](2) (10) and the corresponding olef
in. 4c-e catalyze the head-to-tail dimerization of tert-butyl acetylene by
an insertion/sigma -bond metathesis mechanism involving [(Pr-i(2)-ATI)Al(C
dropC ' Bu)][B(C6F5)(4)] (13) and [(Pr-i(2)-ATI)Al(CH=C(' Bu)C dropC ' Bu)]
[B(C6F5)(4)] (14) intermediates. 13 crystallizes as the dinuclear dicationi
c complex [ (Pr-i(2)-ATI)Al(mu -C dropC ' BU)](2)][B(C6F5)(4)](2). 5PhCl fr
om chlorobenzene. 4e catalyzes the polymerization of propylene oxide and 2a
catalyzes the polymerization of methyl methacrylate. 4c,e react with ethyl
ene-d(4) by beta -H transfer to yield ((Pr-i(2)-ATI)AlCD2CD2H][B(C6F5)(4)]
initially.
Polyethylene is also produced in these reactions by an unidentified active
species.