Technetium V Complexes

Tc(gluconate) and Tc(glucoheptonate) have been the earliest products of Tc(V) used as radiotracers for renal imaging (De Kieviet 1981 Johannsen and Spies 1988). The compounds were shown to contain a Tc=0 core, but their structures are not completely defined, probably because of more than one stable species at carrier-added level (De Kieviet 1981). However, the x-ray structure of similar Tc complexes with similar ligands (Davison et al. 1987 DePamphilis et al. 1974 Fig. 2.1.2), indirectly supports the formulation as TcO(G1u)2, even though the structure of TcO(Ox)(OxH) demonstrates the possibility of another species with a Tc=0 core (Abrams et al. 1991). 

These compounds are easily obtained in high yields at no carrier-added level, and they are suitable precursors in the synthesis of new Tc complexes by ligand exchange (or transchelation) (Spies et al. 1980). Other polyhydroxy or hydroxyl acids have been under investigation, such as glycolate, glucarate, tartrate, or citrate, which have been used in transchelation procedures. 

Compound Oxidation state core Geometry Coordinated number Charge Reference 

DMSA dimercaptosuccinic acid, EDTA ethylenediaminetetraacetic acid, HMPAO hexamethyl propyl-eneamine oxime, DADS J yM-bis(mercaptoacetyl)ethylenediamine, DADT diaminodithiol, ECD ethylcysteinate dimer, MAG3 mercaptoacetyltriglycine, NOEt Et(OEt)NCS2, DTPA diethylene triamine pentaacetate, MDP methylenediphosphonate, HIDA N-(2,6-dimethylphenylcarbamoylmethyl) iminodiacetic acid, DMPE l,2-bis(dimethylphosphino) ethane, BATO boronic acid technetium oxime, MIBI methoxyisobutyl isocyanide 

Two different Tc-dimercaptosuccinic acid (DMSA) complexes are in clinical use, Tc(III)-DMSA with high binding affinity for renal tubuli and Tc(V)-DMSA with tumor affinity. 

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Although technetium(V) complexes have been studied extensively in order to design new radiotracers, investigations of in vivo reactive complexes are still in the formative stages and their potential for mimicking biological substrates is not yet predictable. It is the intention of this review to give an introduction into... 

Technetium(V) complexes with exclusively phosphorus donors and the [Tc=0] core are obviously not stable. The lack of charge compensation leads to Tc " compounds by further reduction, or to hydrolysis. Pure phosphorus coordination is then possible only if the [0=Tc=0]" core is present, as described in the following section (Scheme 36). 

Technetium(V) complexes with terminal main groups other than oxo are very rare. The terminal [M=S] group is isoelectronic with [M=0], but as expected is much more sensitive towards hydrolysis. The Tc sulfido complexes [TcS(edt)2] (224) and [TcSCl2(HB(pz)3)] are prepared by methods known from Mo or Re chemistry. Blood-red (224) is made from the Tc complex [TcCle] (69) in the presence of a tenfold excess of (83), while the sulphido complex... 

Tetradentate S N N S aminothiolato ligands found considerable interest since their complexes represent structural analogues of the neutral technetium(V) complex [TcO(ECD)] (H3ECD = A, A -l,2-ethylenediylbis-L-cysteine diethylester, (160) with R = = H,... 

Technetium(V) complexes with /u,v(ohydroxyphenyl)phenylphosphine and (o-hydroxyphenyl)diphenylphosphine ligands were prepared by metathesis reactions with the appropriate Tc(V) precursor and/or by reduction/ligand-exchange reactions with ammonium pertechnetate [530]. It was expected that the combination of one soft phosphine P-donor and two hard phenolate O-donors in the chelate should stabilize Tc centers in intermediate oxidation states. 

Structural Properties of Five-Coordinate Nitrido Technetium(V) Complexes. . 91... 

Epps LA, Burns HD, Lever SZ et al (1978) Brain imaging agents synthesis and characterization of (N-piperidinylethyl)hexamethyl diaminodithiolate oxo-technetium(V) complexes. Int J Appl Radial Isot 38 661-664... 

Morgan G, Deblaton M, Hussein W, Thornback J, Evrard G, Durant F, Stach J, Abram U, Abram S (1991) Rhenium(V) and technetium(V) complexes with N-(2(lH-pyrolmethyl))-N -(4-pentene-... 

Recently, the preparation and crystal structure of [(C6Hs)3PNP(C6Hs)3]-[TcOCU], a five-coordinate technetium(V) complex have been achieved. The tetrabutylammonium salt, (Bu4N)[TcOCl]4, can be easily prepared and isolated from the reduction of pertechnetate(VII) ion in 12IV hydrochloric acid in nearly quantitative yield. It is soluble in a variety of polar organic solvents and reacts easily with a variety of ligands to form 0x0 technetium(V) complexes. ... 

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