Dioximes, technetium complexes

Dioxazolines, synthesis, 30 271 Dioximes, technetium(III) complexes, 41 33-36 Dioxocyclam, 45 96 Dioxohexakis(trimethylsilylmethyl)-... 

Dioxime type ligands can be considered as Schiff base bischelates (Deutsch et al. 1978 Bandoli et al. 1986). The first complexes with oxime ligands were described as mono-capped Tc(dioxime)3(//OH)SnCl3 (dioxime = dimethylglyoxime) complexes (Treher et al. 1989). The boronic adducts of technetium oximes - (BATOs) (Fig. 2.1.19) - were well characterized, and some could be used both as myocardial and cerebral perfusion agents. The complexes are neutral technetium is coordinated to three N-bonded dioxime molecules and to one Cl or Br atom in an axial position (seven covalent bonds). 

Tris(dioxime) complexes that are capped with a boryl group BR at only one end of the molecule are also known, e.g., with technetium(III) [227, 228] and rhenium(III) [229]. 

An alternative approach to cationic myocardial imaging agents has been the development of neutral seven-coordinate Tc(III) complexes based on 1,2-dioxime ligands (dioximeH2) with one end capped by a boronic acid derivative (19, 253). These complexes are generally referred to as BATOs (boronic acid adducts of technetium dioximes) and have the general structure [TcX(dioximeH)2(dioxime)BR ] (X = Cl, Br R = alkyl) shown in 18. 

Attempts to isolate clathrochelate technetium (III) tris-dioxi-mates via template cross-linking three dioxime molecules with alkylboronic acid have not been successful. Only semiclathrochelate TcNx(HNx)2(BR2)Hal and TcDm(HDm)2(BR2)Hal complexes (where HaF is Cr, Br R is CH3 and A1-C4H9) were prepared [87, 88],... 

Complexes with Dioximes, Schiff Bases, and Other Nitrogen Ligands Complexes with Monodentate Phosphines and Related Ligands Complexes with Bidentate Phosphine, Arsine, and Related Ligands Complexes with Sulfur Ligands Nitrosyl and Thionitrosyl Complexes VII. Technetium(IV)... 

Treher EN, Francesconi LG, Gougoutas JZ, Malley M, Nunn A (1989) Mono-capped tris dioxime complexes of technetium (III) synthesis and structural characterization of TCX (dioxime)3, B-R (X=C1, Br dioximedimethylglyoxime cyclohexanedioxime R=CFl3, C4FI9). Inorg Chem 28 3411-3416... 

Half-lives for hydrolysis of Tc—Cl to Tc—OH have been determined for four so-called BATO complexes. These contain a semiencapsulating tris-dioxime ligand with a borate cap and the chloride ligand the technetium is seven-coordinate, (21), with Y = OH or Me and either R = Me or pairs of R comprise cyclohexyl rings. Rate constants lie in the range 19 to 1.2 x lO s" for the four complexes examined, at 20 to 37 There is also some very qualitative kinetic information on base hydrolysis and ligand exchange (Cl for Br and vice versa) in this type of complex. These reactions have half-lives of minutes in media such as aqueous acetonitrile. ... 

An improved synthesis of MeB(OH)2 was described via the reaction of B(OCHM 3 with MeLi and subsequent hydrolysis the compounds are useful intermediates for the preparation of technetium-99m dioxime complexes. PhB(OCH2CF3)2 was... 

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