New titanium imido complexes containing piperazine-based diamido-diamine ligands

Syntheses of the new piperazine derivatives 1,4-bis(2-amino-4-tert-butylben zyl)piperazine (2) and 1,4-bis(2-trimethylsilylamino-4-R-benzyl)piperazine (R = H 3 or Bu' 4; H2L1 and H2L1 respectively) are described along with the X-ray crystal structure of 2. Treatment of H2L1 and H2L1 with n-butyl lith ium gives the amido derivatives Li2L1 (5) and Li2L2 (6), which react with [ Ti(NBu')Cl-2(py)(3)] to form [Ti(NBu')(L-1)] (7) and [Ti(NBu')(L-2)] (8). R eaction of Li2L1 with [Ti(N-4-C6H4Me)Cl-2(py)(3)] gives the corresponding a rylimido homologue [Ti(N-4-C6H4Me)(L-1)] (9). The X-ray structure of 8 show s a strongly transoid disposition of the aryl rings of the L-1 ligand and t his geometry is maintained in solution. Somewhat surprisingly 7 does not un dergo tert-butylimide/arylamine exchange with 4-methylphenylamine to form 9 . The related compound N,N'-bis(2-trimethylsilylaminobenzyl)-N,N'-dimethyl- 1,3-diaminopropane (12, H2L3) and its lithium salt Li2L3 (13) are also desc ribed. However, reaction of 13 with [Ti(NBu')Cl-2(py)(3)] affords no tracta ble product. (C) 1999 Elsevier Science S.A. All rights reserved.