Isopropylideneimino ligand

The stronger coordination of the isopropylideneimino ligand to silicon is also confirmed by a substantial upheld shift of the silicon resonance, from —29.0 in 4c to —52.8 ppm in 7 (in CDC13 solution at 300 K).20 An additional manifestation of the stronger donor property of the isopropylideneimino group is found in the relative ease of ionization of hexacoordinate complexes with this ligand. This subject is discussed in Section III.B.2. 

The data in Table XX permit an assessment of the donor strength of the new isopropylideneimino ligand.20,52 Comparison of the bond lengths between the two chelate families (Table XX) clearly indicates stronger... 

Ionization of 66 is unexpected not only because it is the only dihalo-complex in this series which ionizes, but because the previously reported dihalo-dimethylamino-coordinated complexes, 35, 37, and 38, were completely resistant to ionization. Ionization of 66 thus constitutes additional evidence for the stronger donor property of the isopropylideneimino ligand group. 

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