Technetium(V) and rhenium(V) complexes with Schiff-base ligands containing the ONNNO donor atom set. Crystal structure of [N,N′-3-azapentane-1,5-diylbis(salicylideneiminato)(3–)-O,O′,N,N′,N″]-oxotechnetium(V)

Abstract

The reactions of quinquedentate Schiff-base ligands derived from salicylaldehyde and diethylenetriamine (H₃L¹) or 3,3′-diamino-N-methyldipropylamine (H₂L²) with [MO(eg)₂]^–(M = Tc or Re; H₂eg = ethylene glycol) have been investigated. The complexes [MOL¹] and [MOL²]⁺ were produced and characterized by the usual physicochemical measurements. In particular the crystal structure of [TcOL¹] was determined by single-crystal X-ray diffraction methods. Crystals are monoclinic, space group P2₁/c, with a= 9.459(8), b= 9.437(7), c= 21.768(12)Å, β= 99.08(5)°, and Z= 4. X-Ray diffraction provided 2 097 observed reflections (up to 2θ= 50°) and the structure has been refined by full-matrix least-squares methods to R= 0.053. The compound consists of discrete TcOL¹ molecules with one methanol methanol molecule of crystallization also present in the crystal lattice. One of the oxygen atoms of the quinquedentate ligand is located trans to the technetium–oxo bond, while the remaining four donor atoms occupy the equatorial sites around the Tc atom which resides in a highly distorted octahedral co-ordination environment. The distance between the deprotonated N atom and Tc [1.894(8)Å] is significantly shorter than the average for Tc–N single bond lengths.