Synthesis, Isolation and Structural Investigation of Schiff‐Base Alkoxytitanium Complexes: Steric Limitations of Ligand Coordination

Abstract

This paper reports the reaction of Ti(OiPr) 4 with a series of Schiff-base ligands. The Schiff-base proligands 1a-l are synthesised by the condensation of salicylaldehyde with a range of primary alkylamine and aniline derivatives. The treatment of 1a-f with Ti(OiPr) 4 yields the octahedral bis(aryloxyimine)Ti(OiPr) 2 complexes 2a-f. X-ray crystal structure analysis of 2c, 2d and 2e reveals complexes with a trans-aldiminato oxygen atom and cis-N,cis-alkoxide ligand arrangement about the central metal atom. The reactions of Ti(OiPr) 4 with the ligands 1g and 1h result in a sterically induced ligand rearrangement to form the octahedral complexes 2g and 2h, also characterised by X-ray diffraction experiments, in which the nitrogen atoms of the O,N-chelate are now trans-orientated at the titanium centre.1 H NMR analysis reveals significant deshielding of the isopropoxide methine proton, in-

Dioximate‐ and Bis(salicylaldiminate)‐Bridged Titanium and Zirconium Alkoxides: Structure Elucidation by Mass Spectrometry

“…The tetrameric complex shown in Scheme 1 was obtained from 2,4-pentanedioxime, in which the dioximate ligands both bridge dimeric titanium alkoxide units and interconnect two of the dimeric units 3. In the absence of an additionally coordinating substituent the salicyclaldiminate-substituted derivatives [M(OR) 2 (SA) 2 ] (M=Zr, Ti; SA=salicylaldiminate) have the same geometry as the corresponding complexes [M(OR) 2 (β-diketonate) 2 ], that is, with the OR groups in positions cis to each other 4. This structural motif was also found in a complex in which the two SA ligands are connected through a C 6 H 4 –S–S–C 6 H 4 bridge (Scheme 1, bottom left)5 as well as in the hydrolyzed compound [{(salen)TiO} 2 ] (salen= N , N ′-ethylenebis(salicylimine)), in which the two Ti atoms are bridged by two oxo groups 6.…”

FI Catalyst for Polymerization of Olefin

“…When FI catalysts possess extremely bulky groups on the imine-Ns (N-C6H3-2,6-R 2 , R: Me, iPr), they can adopt a cis-O, trans-N and cis-X (X= O-i-Pr) arrangement. Any further increase in the steric bulk of the R 1 substituent (N-C6H3-2,6-Ph2 or N-CHPh2) forces one of the N-Ti bonds to become dissociated, resulting in a five-coordinated complex [36]. However, FI catalysts generally exist as a mixture of isomer a, which is normally predominant (trans-O, cis-N, and cis-Cl arrangement: C2 symmetry), and isomer b (cis-O, cis-N, and cis-Cl arrangement: C1 symmetry [36,37].…”

“…Any further increase in the steric bulk of the R 1 substituent (N-C6H3-2,6-Ph2 or N-CHPh2) forces one of the N-Ti bonds to become dissociated, resulting in a five-coordinated complex [36]. However, FI catalysts generally exist as a mixture of isomer a, which is normally predominant (trans-O, cis-N, and cis-Cl arrangement: C2 symmetry), and isomer b (cis-O, cis-N, and cis-Cl arrangement: C1 symmetry [36,37]. These isomers are often fluxional and can mutually transform each other on a nuclear magnetic resonance (NMR) time scale [35].…”

FI Catalysts: Unique Olefin Polymerization Catalysis for Formation of Value-added Olefin-based Materials

“…X-ray analysis has established that, in the solid state, an FI catalyst normally exists as the isomer A, meaning, it has a trans-O, cis-N, and cis-Cl arrangement, and thus C2 symmetry 31), 59) . The C2-symmetric nature implies that the catalyst may be an isospecific catalyst for propylene polymerization, but actually not 60) . When FI catalysts possess extremely bulky groups on the imine-Ns (N-C6H3-2,6-R2, R: Me, i-Pr), they can adopt a cis-O, trans-N and cis-X (X O-i-Pr) arrangement.…”

“…When FI catalysts possess extremely bulky groups on the imine-Ns (N-C6H3-2,6-R2, R: Me, i-Pr), they can adopt a cis-O, trans-N and cis-X (X O-i-Pr) arrangement. Any further increase in the steric bulk of the R 1 substituent (N-C6H3-2,6-Ph2 or N-CHPh2) forces one of the N-Ti bonds to become dissociated, resulting in a five-coordinated complex 59), 60) . In solution, however, FI catalysts generally exist as a mixture of isomer A, which is normally predominant (trans-O, cis-N, and cis-CI arrangement: C2 symmetry), and isomer B (cis-O, cis-N, and cis-CI arrangement: C1 symmetry) 40),50),61)～64) .…”