CRYSTAL-STRUCTURES OF TITANIUM(III) BIS(ACETYLIDE) TWEEZER COMPLEXES WITH ALKALI-METAL CATIONS

Crystal structures of the Ti(III) tweezer complexes C5HMe4)(2)Ti(sigma -C=CSiMe3)(2)](-)[Li(THF)(2)](+) (2a), [(C5HMe4)(2)Ti(sigma-C=CSiMe3)( 2)]Na--(+) (3) and [(C5HMe4)(2)Ti(sigma-C=CSiMe3)(2)]Cs--(+) (5) have been determined. In all of them the alkali metal cation is placed away from the Ti-C-alpha 1-C-alpha 2 plane at the distance: Li+ 0.511 Angs trom, Na+ 1.023 Angstrom and Cs+ 0.521 Angstrom. The reason for the de viation of Li+ in 2a is the asymmetrical orientation of the THF ligand s in the [Li(THF)(2)](+) cation with respect to the Ti-C-alpha 1-C-alp ha 2 plane, which seems to release the steric congestion between the T HF ligands and the trimethylsilyl groups. In 3 and 5, the molecules fo rm polymer chains with a weak intermolecular bonding interaction betwe en the cations and one of the C5HMe4 ligands of the neighbouring molec ule in a sandwich manner.