Monosaccharide Ligands in Organotitanium and Organozirconium Chemistry

Abstract

Despite their advantageous properties, monosaccharide-derived ligands have rarely been applied in the synthesis of organometallic compounds and thus little is known about their coordination capabilities. Most of the established monosaccharide-metal complexes are based on late transition metals such as Rh, Pd and Pt [1]. Among early transition metals, monosaccharide complexes containing Ti and Zr are of importance [2]. Although the information pertaining to their metal-ligand binding sites is scarce, both late and early transition metal complexes of modified monosaccharides have been successfully applied as chiral reagents and catalysts in stereoselective synthesis [3]. Synthesis of Organotitanium Carbohydrate CompoundsWithin this research topic we are interested in the ability of pyranosides to coordinate to varying titanium precursors and the use of the resulting complexes in stereoselective synthesis. In particular we are investigating the 2-and 3-positions of pyranosides as coordination sites for organometallic complexes of the early transition metal Ti. The torsion angle between the oxygen functions of C2 and C3 of the pyranosidato ligand may determine whether a mononuclear chelate complex or a dinuclear compound with a bridging coordination between two Ti atoms is formed.Our interest in the coordination chemistry of Ti when reacted with carbohydrate ligands has led to previously reported reactions [4,5]. The reaction of methyl-4,6-Obenzylidene-b-D-glucopyranoside (b-MeBnGluH 2 ) with the organotitanium complex Cp à TiCl 3 in the presence of triethylamine gave the dinuclear titanium complex (T-4-R; T-4-R)bis[chlorido(h 5 -pentamethylcyclopentadienyl)][m-(methyl-4,6-O-benzylidene-b-D-glucopyranosidato-1kO 2 , 2kO 3 )][m-(methyl-4,6-O-benzylidene-b-D-glucopyranosiActivating Unreactive Substrates: The Role of Secondary Interactions. Edited