The cationic technetium-99 complex trans-[99TC(dmpe)2Cl2]+, where dmpe is bis(1,2-dimethylphosphino)ethane or (CH3)2P-CH2-P(CH3)2, has been prepared and characterized by single-crystal, x-ray structural analysis. The technetium-99m analog, trans-(99mTc(dmpe) 2Cl2]+, has also been prepared and shown to yield excellent gamma-ray images of the heart. The purposeful design, characterization, and synthesis of this technetium-99m radiopharmaceutical represents a striking application of fundamental inorganic chemistry to a problem in applied nuclear medicine.

Abstract.trans- [TcClz(diars) The six-coordinate Tc complex has trans chloride ligands and four As atoms from two nearly coplanar o-phenylenebis(dimethylarsine) ligands, giving ideal D2h symmetry in each case (C1-salt, site symmetry 1; C102 salt, site symmetry 2). The mean Tc-As distance is 2.512 (2) A (four independent distances, range 0.011 A), whereas those for Tc-C1 are 2.348 (8), 2.288 (7), and 2.329 (1) A. The C10 4 salt is yelloworange, whereas the C1-salt is dark red.

Communications to the Editor 2103 HCIO» and either ~2 M 2-propanol (to scavenge -Cl) or 0.1 M Fe(CI04)3 [to scavenge CoM(N4)]. Photochemical techniques are described elsewhere.15,22 (24) If we take K0 ~0.1 M-1 for the association of the two +2 complexes in solutions 0.1 M in ionic strength, then = ( ß0 + "*) ~(1,4 + 5) kcal mol-1. In this estimate we have used98,12 kw = (KT/h)e~A6w IRT ~109 s-1 as the rate constant for water loss from Co(N4)(OH2)22+.(25) This definition neglects a small entropy change due to solvent compressions on going from the unbound state to the transition state.(26) Electron affinities are 0.08 eV for • 327 compared with 3.56 and ~3.3

The positive ion fast atom bombardment mass spectra of a series of monovalent Technetium(III) cation complexes yield intense [C]+ ions and distinctive fragmentation information.

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