CONFIGURATIONAL REARRANGEMENTS IN CIS-M(AA)2X2, CIS-M(AA)2XY, AND CIS-M(AB)2X2 COMPLEXES .6. BIS(CHELATE)BIS(2,6-DIISOPROPYLPHENOXY)TITANIUM SYSTEMS (CHELATE= ACETYLACETONATE, 8-HYDROXYQUINOLINATE, AND 8-HYDROXYQUINALDINATE)

For a series of bis(chelate)bis(2, 6-diisopropylphenoxy)titanium complexes [chelate = acetylacetonate (acac), 8-hydrox-yquinolinate (ox), and 8-hydroxyquinaldinate (quin)] an NMR total line shape analysis of isopropyl methyl group exchange (inversion) is reported, along with data for acetylacetonate (acac) methyl group exchange for the corresponding acac complex. Activation energies (kcal/mol) and entropies (eu), in m-dichlorobenzene solutions, for inversion are respectively 6.3 ± 1.7 and -36.5 ± 5.7 (acac), 14.7 ± 0.8 and -9.7 ± 2.2 (quin), and 21.2 ± 1.3 and 2.2 ± 3.3 (ox). For acac methyl group exchange, the corresponding kinetic data are (in m-dichlorobenzene solution) 13.8 ± 0.3 and -10.6 ± 1.0. Dramatic differences between kinetic parameters suggest that the ox and quin complexes possess a different rearrangement route than that for the acac complex. On the assumption that the ox and quin complexes retain the same structure in solid and solution phases, the isopropyl methyl group exchange is identified as resulting from the process cis(phenoxy),cis(N),trans(O)-Δ(A) ⇄ cis(phenoxy),cis(N),trans(O)-A(Δ), This rearrangement stereochemistry can only be generated via a Ti-N bond-rupture mechanism occurring through a trigonal-bipyramidal axial intermediate. © 1979, American Chemical Society. All rights reserved.