93427-02-2Relevant articles and documents
Synthesis, characterization, and electrochemical properties of technetium complexes containing both tetradentate schiff base and monodentate tertiary phosphine ligands: Single-crystal structure of trans-(N,N′-ethylenebis(acetylacetone iminato))bis(triphenylphosphine)technetium(III) hexafluorophosphate
Jurisson, Silvia S.,Dancey, Keith,McPartlin, Mary,Tasker, Peter A.,Deutsch, Edward
, p. 4743 - 4749 (2008/10/08)
A series of nine technetium(III) complexes of the type trans-[TcIIILY2]+, where L represents a tetradentate Schiff base ligand and Y represents a monodentate tertiary phosphine ligand, has been synthesized and characterized. This series includes the five Schiff base ligands N,N′-ethylenebis(acetylacetone iminato) ((acac)2en), N,N′-ethylenebis(tert-butyl acetoacetate iminato), N,N′-ethylenebis(benzoylacetone iminato), N,N′-ethylenebis(3-bromoacetylacetone iminato), and N,N′-ethylenebis(salicylideneaminato). These complexes are prepared by reaction of the corresponding technetium(V) Schiff base complex, trasn[TcVL(O)OH2]+, with excess phosphine, which concomitantly reduces and coordinates to the technetium center. The hexafluorophosphate salt of the title complex, with L = (acac)2en and Y = PPh3 (molecular formula TcP3F6N2O2C48H 48, formula weight 990.83), has been characterized by single-crystal X-ray structural analysis refined to a conventional R factor of 0.109. Further refinement was precluded by severe disorder in the PF6- anions. Rectangular crystals of this salt crystallize in the triclinic space group P1, with a = 19.037 (5) ?, b = 16.339 (3) ?, c = 15.454 (4) ?, α = 95.37 (2)°, β = 96.47 (2)°, γ = 91.32 (2)°, and Z = 4. The technetium(III) center is approximately octahedrally coordinated with the two N and two O donor atoms of the tetradentate Schiff base ligand in the equatorial plane and the two phosphine P atoms in the trans apical positions with an average Tc-P bond length of 2.51 (2) ?. Other complexes in this series have been characterized by some combination of elemental analyses, IR and visible-UV spectrophotometry, thin-layer and column chromatography, and cyclic voltammetry (CV). All complexes exhibit characteristic charge-transfer bands in the visible region of the spectrum. The position of the lowest energy metal-to-ligand charge-transfer (MTLCT) band is a function of both the nature of the Schiff base ligand and the nature of the substituents bonded to the donor P atoms. CV shows that in acetonitrile, with use of a glassy-carbon electrode, every technetium(III) complex in this series exhibits a reduction to Tc(II) and an oxidation to Tc(IV). The E°′ values of these Tc(IV)/Tc(III) and Tc(III)/Tc(II) redox couples also depend upon the nature of the Schiff base ligand and on the nature of the substituents bonded to the donor P atoms. For both couples the values of E°′ are linearly related to the energies of the MTLCT bands.
