Synthesis and structural study of titanium bis(sulfonamido) bis(amide) complexes

Reaction of the titanium tetraamide Ti(NMe2)(4) with various bis(sulfonamide) ligands resulted in the clean formation of the bis(sulfonamido)Ti(NMe2)(2) complexes and N,N-dimethylamine. We have characterized the resulting racemic and resolved bis(sulfonamido)Ti(NMe2)(2) complexes by X-ray crystallography to explore differences in the bonding and geometry of the ligand in these complexes. From the crystal structures, the ligand is found to bind through the sulfonyl oxygens as well as the sulfonamido nitrogens. The Ti-N distances of the sulfonamido groups range from 2.048(3) to 2.103(2) Angstrom, while the Ti-N distances of the amides are significantly shorter, between 1.858(3) and 1.896(3) Angstrom The structures indicate that the bonding of the ligand to the metal can be either eta(3) or eta(4), with the Ti-O sulfonyl distances ranging from 2.167(2) to 2.447(4) Angstrom. We have synthesized bis(sulfonamido)Ti(NMe2)(2) complexes with bis(sulfonamide) ligands of varying sizes and found that the bulk of the ortho substituent of the aryl groups (H vs Me vs i-Pr) dictates the position of the aryl rings in the solid state. The bis(sulfonamido)Ti(NMe2)(2) complexes described here are related to the proposed catalysts in the asymmetric alkylation of aldehydes.