Titanium(IV) complexes of the crystallographically characterised fluorene-Schiff base N-2-fluorenyl(salicylideneimine) and related bi- and tetradentate ligands

Abstract

Schiff base ligands have been prepared by the condensation of 2-aminofluorene with salicylaldehyde ( 1, flusalH) or 3-methoxy-2-hydroxybenzaldehyde ( 2, MeOflusalH). Compound 1 reacts with TiCl 4 in a 1:1 stoichiometry to afford [TiCl 3(flusal)] ( 3) and in a 2:1 ratio to yield [TiCl 4(flusalH) 2] ( 4). The reaction of excess TiBz 4 with compound 1 results in the isolation of the octahedral Ti(IV) complex [Ti(flusal) 2(flusalaBz) 2] ( 5). Crystallographic and spectroscopic data for the latter indicate a complex containing two Schiff base ligands present as conventional N,O chelates and a further two ligands in which the CN function is reduced by the addition of benzyl and hydrogen moieties producing an O-bound species with pendant amine. The single crystal X-ray diffraction structure of compound 1 has been obtained and compared with the published data for compound 5. Similar ligand alkylation to that observed in compound 5 is also achieved by the reaction of organolithium reagents with compounds 1 and 2; the reaction of PhLi and compound 2 followed by aqueous hydrolysis affords MeOflusalaPhH ( 6). Although reactivity does occur between TiCl 4 and compound 6, the products could not be fully characterised. Thus tetradentate reduced Schiff base ligands were synthesised by the reaction of salenH 2 with MeLi or PhLi, giving salenaMe 2H 2 ( 7) and salenaPh 2H 2 ( 8), respectively. Reaction of compound 8 and TiCl 4 affords the quadruply deprotonated amido complex [Ti(salenamidoPh 2)] ( 9), which hydrolyses in air to the μ-oxo amine complex [Ti(salenaPh 2)O] ( 10).