Schiff bases rhenium complexes

Schiff bases provide useful mixed donor sets. The carbonyl function of the most frequently used ligands is derived from either 1,3-dicarbonyl compounds or salicylaldehyde. Favourable combinations involve O-, N- and S-donor atoms. A range of technetium and rhenium complexes exist with bi-, tri-, tetra- and pentadentate ligands. The geometry of these complexes depends on the number and type of coordinating atoms as well as on the chain length between the donor atoms in the SchifF-base ligands. 

Schiff base complexes to aromatic silyl enol ethers/ " olefins/ sugars,Mn ° Schiff base complexes, " and rhenium(III) complexes " has been reported. Similar reactions are observed with the Mn (N)porphyrin complexes. The reaction products are dependant on the nature of the Schiff base ligand, both the yield and the enantiomeric excess being affected. " Salen nitridomanganese(V) complexes have been incorporated into Zeolite... 

Rhenium(IV) complexes with only one bidentate ligand have been described for chelating phosphines, Schiff bases, and A-heterocycles. The synthetic approaches are different and involve simple ligand exchange procedures as well as reduction of rhenium(V) or oxidation of rhe-nium(III) compounds. 

Mechanisms of formation of rhenium(I), -(III), -(IV), and -(V) complexes with bidentate Schiff bases have been discussed in relation to available structural data. This discussion includes a few qualitative comments on reactivities.The course of substitution at [ReBr ] " in aqueous hydrochloric acid, and at [ReClg] in hydrobromic acid, was monitored by periodic precipitation by Cs and identification of the solids produced. Species identified are shown in equations (2) and (3). These observations demonstrate the important role played by the effect... 

A connectivity of 1 is given for side chain metal-containing polymers as 1 in which the metal complex is connected via one bond to the main chain [11]. Additional examples for other connectivities are (Fig. 1-8) connectivity 2 in metal(yne)s 2 [12] connectivity 3 in arsenic(III) sulfide 3 connectivity 4 in a polymeric methyl rhenium oxide of the formula Ho.5[(CH3)o.92Re03] co 4 [13] or polymeric phthalocyanines 5 [14] connectivity 8 in lanthanide complexes of bis(tetradendate) Schiff base bridging ligands 6 [15]. 

Other chiral metal catalysts such as iridium, osmium, and rhenium catalysts have also been utilized for asymmetric cyclopropanation. In particular, iridium catalyst gave exceptional enantio- and diastereoselectivities. Chiral Ir(III) salen complexes, which contain a-coordinated aryl ligands, were found to catalyze the cyclopropanation of st3rrene derivatives with TDA. Higher yields (99%), higher diastereoselectivity t/c = 1 99), and enantioselectivity (99% ee) were observed when the reactions were conducted at lower temperature (—78°C) (98). For osmium, an Schiff-based complex of [Os(fBu-salch)(OH)Cl] (H2tBu-salch... 

The IR spectra of ReO(L), where L is an A 2>A, S-peptidic chelating ligand, contain vRe=0 at 986 cm h " vReO modes were seen near 940 cm for oxorhenium(V) complexes with Z)-penicillamine methyl ester. Rhenium ditho-carbamate complexes such as [Re0(S2CNEt2)2]2(06H402-l,4) have vRe=0 at 960 cm h ReOCl3(HL), where HE is a Schiff base derived from 2,6-diformyl-4-methylphenol and C6H5NH2, shows vRe=0 at 1000 cm and vReCl at 320 cm h ... 

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