The reaction of the aminophenols 2-(CH
2L)-6-R-C
6H
3OH (R = Ph, L = NMe
2,
1a; R =
tBu,L = NMe
2,
1b; R =
tBu, L = NC
4H
8,
1c; R =
tBu, L = NC
5H
10,
1d) with 1 equiv of AlMe
3affords the corresponding dimethyl Al complexes {2-(CH
2L)-6-R-C
6H
3O}AlMe
2 (R = Ph, L =NMe
2,
2a; R =
tBu, L = NMe
2,
2b; R =
tBu, L = NC
4H
8,
2c; R =
tBu, L = NC
5H
10,
2d) inhigh yields. Compounds
2a-
d appear to be monomeric, on the basis of X-ray analysis for
2b,
d and NMR data for
2a-
d, and are stable in the presence of THF. {2-(CH
2NMe
2)-6-Ph-C
6H
3O}AlMe
2 (
2a) cleanly reacts with B(C
6F
5)
3 to yield the dinuclear cationic Al species
3a+. X-ray diffraction analysis shows that the cation
3a+ can be seen as an adduct of thethree-coordinate cation {2-(CH
2NMe
2)-6-Ph-C
6H
3O}AlMe
+ and the neutral precursor
2a, inwhich the two Al centers are connected via a
2-O aminophenolate bridge. Similarly, thereaction of Al dimethyl complexes
2b-
d with B(C
6F
5)
3 yields dinuclear cationic Al species
3b-
d+/
3b'-
d'
+ (
3b+/
3b'
+ in a 1/1 ratio;
3c,
d+/
3c',
d'
+ in a 3/1 ratio, respectively) asdiastereomeric mixtures. Cations
3b-
d+/
3b'-
d'
+ adopt a structure similar to that of cation
3a+, as determined by X-ray crystallography analysis for
3b'
+ and 2D NMR studies for
3a+and
3c,
d+/
3c',
d'
+. All the formed dinuclear cations are quite stable and robust in solution,and no fluxional behavior for any of them was observed up to 80
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C in C
6D
5Br. Cations
3b-
d+/
3b'-
d'
+ react with a Lewis base such as THF to afford the corresponding THF adductcation
4b-
d+ along with 1 equiv of the corresponding neutral precursor
2b-
d. In contrast,
3a+ reacts with THF to yield unidentified species.
3a+ and
3c,
d+/
3c',
d'
+ are inactive inethylene polymerization, but cations
3b-
d+/
3b'-
d'
+ polymerize PO with moderate activityto yield low-molecular-weight PPO.