Rhenium and technetium complexes from pentadentate (N 3 O 2 ) and tetradentate (N 2 O 2 ) Schiff base ligands

Abstract

The rhenium(V) and technetium(V) complexes: [ReO(apa)], [{ReO(epa)} 2 O], and [TcOCl(epa)] have been prepared from a potentially pentadentate N 3 O 2 ligand, N,N′-3-azapentane-1,5-diylbis(3-(1-iminoethyl)-6-methyl-2H-pyran-2,4(3H)-dione) (H 3 apa), or a potentially tetradentate N 2 O 2 ligand, N,N′-ethylene-diylbis(3-(1-iminoethyl)-6-methyl-2H-pyran-2,4(3H)-dione) (H 2 epa). The N 2 O 2 complexes were synthesized in low yields. There was also evidence indicating that H 2 ppa, N,N′-propylene-diylbis(3-(1-iminoethyl)-6-methyl-2H-pyran-2,4(3H)-dione), hydrolyzed in the course of coordination, forms a rhenium complex of the bidentate monoprotic (O,O) dehydroacetate (dha − ), [Re(dha)Cl 2 (OPPh 3 )(PPh 3 )]•EtOH. The structure of this complex was determined by X-ray crystallography. Crystals of [Re(dha)Cl 2 (OPPh 3 )(PPh 3 )] EtOH (C 44 H 37 Cl 2 O 5 P 2 Re•C 2 H 6 O) are monoclinic, a = 11.064(2), b = 24.167(2), c = 16.6687(8) Å, β = 98.779(7)°, Z = 4, space group P2 1 /c. The structure was solved by the Patterson method and refined by full-matrix least-squares procedures to R = 0.030 and R w = 0.025 for 6942 reflections with I ≥ 3σ(F 2 ). Keywords: dehydroacetic acetate based Schiff base ligands, rhenium, technetium, N 3 O 2 Schiff base, N 2 O 2 Schiff base, oxygen transfer.