Application of technetium and rhenium carbonyl chemistry to nuclear medicine. Preparation of [NEt4](2)[TcCl3(CO)(3)] from [NBu4][TcO4] and structure of [NEt4][Tc-2(mu-Cl)(3)(CO)(6)]; structures of the model complexes [NEt4][Re-2(mu-OEt)(2)(mu-OAc)(CO)(6)] and [ReBr({-CH2S(CH2)(2)Cl}(2))(CO)(3)]

A detailed investigation of the one-pot synthesis of [NEt4](2)[MX3(CO)(3)] [M = Tc (1a) or Re (1b); X = Cl-, Br-] is presented. The intermediates [NEt4][Tc-2-(mu-Cl)(3)(CO)(6)] (2a), [NBu4][Tc-3(mu(3)-H)(mu-H)(3)(CO)(9)] (3) and [Tc-3(mu-H)(3)(CO)(12)] (4) have been isolated and characterized. The X-ray structure of (2a) is described. Complex (2a) crystallizes in the monoclinic space group P2(1)/c with a = 19.491(6), b = 18.323(2) and c = 17.497(9) Angstrom, and beta = 97.59(2)degrees. Quantitative conversion of (2a), (3) and (4) into the aqua-ion [M(OH2)(3)(CO)(3)](+) [M = Tc (5a) or Re (5b)] is described. To evaluate an optimal and simple chelating group for the ''fac-M(CO)(3)'' moiety, the reaction with the bidentate thioether ligand Cl(CH2)(2)S(CH2)(2)S(CH2)(2)-Cl (qyp) has been investigated and the structure of the neutral complex [ReBr(qyp)(CO)(3)] (6) is described. Complex (6) crystallizes in the monoclinic space group P2(1)/c with a = 15.935(6), b = 2.788(4) and c = 7.955(10) Angstrom, and beta = 98.57(1)degrees. To extend the knowledge about substitution chemistry of organometallic complexes in aqueous solution, the acetato ligand [OOCCH3](-) has been reacted with (1b), resulting in the formation of the dinuclear, acetato-bridged complex [NEt4][Re-2(mu-OH)(2)(mu-OAc)(CO)(6)], which converted into [Re-2(mu-OEt)(2)(mu-OAc)(CO)(6)](-) (7) after recrystallization from EtOH. The X-ray structure of (7) has been determined. Complex (7) crystallizes in the monoclinic space group P2(1)/c with a = 16.288(3), b = 12.4272(10) and c = 13.620(3) Angstrom, and beta = 76.63(1)degrees. For a future application of the small ''fac-M(CO)(3)'' moiety, it seems thus advantageous to combine these two ligand groups in one simple chelating function.