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

Coles, S. J., Hursthouse, M. B., Kelly, D. G. and Toner, A. J. (2000) Titanium(IV) complexes of the crystallographically characterised fluorene-Schiff base N-2-fluorenyl(salicylideneimine) and related bi- and tetradentate ligands. Polyhedron, 19 (2), 177-183. (doi:10.1016/S0277-5387(99)00340-X).

Abstract

Schiff base ligands have been prepared by the condensation of 2-aminofluorene with salicylaldehyde (1, flusalH) or 3-methoxy-2hydroxybenzaldehyde (2, MeOflusalH). Compound 1 reacts with TiCl4 in a 1:1 stoichiometry to afford [TiCl3(flusal)] (3) and in a 2:1 ratio to yield [TiCl4(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 TiCl4 and compound 6, the products could not be fully characterised. Thus tetradentate reduced Schiff base ligands were synthesised by the reaction of salenH, with MeLi or PhLi, giving salenaMe(2)H(2) (7) and salenaPh(2)H(2) (8), respectively. Reaction of compound 8 and TiCl4 affords the quadruply deprotonated amido complex [Ti(salenamidoPh(2))] (9), which hydrolyses in air to the mu-oxo amine complex [Ti(salenaPh(2))O] (10).

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