Structural and 99Tc NMR investigations of complexes with fac-[Tc(CO)3]+ moieties and macrocyclic thioethers of various ring sizes:: Synthesis and X-ray structure of the complexes fac-[Tc(9-ane-S3)(CO)3]Br, fac-[Tc2(tosylate)2(18-ane-S6)(CO)6], and fac-[Tc2(20-ane-S6-OH)(CO)6][tosylate]2

Starting originally from the organometallic precursor [NEt4](2)[TcBr3(CO)(3)] (1b), substitution reactions were performed with the macrocyclic thioethers 1,4,7-trithiacyclononane (9-ane-S-3), 1,4,7,10,13,16-hexathiacyclooctadecane (18-ane-S-6), and 3,6,9,13,16,1 9-hexathiacycloicosanol (20-ane-S-6-OH). The corresponding complexes fac- [Tc(9-ane-S-3)(CO)(3)] Br (2), fac- [Tc-2(tosylate)(2)(18-ane-S-6)(CO)(6)] (3), and fac-[Tc-2(20-ane-S-6-OH)(CO)(6)] -[tosylate](2) (5) were isolated in good yields and characterized spectroscopically by IR,H-1, Tc-99 NMR, and X-ray diffraction methods. In the case of 18-ane-S-6 and 20-ane-S-6-OH the formation of the 1:2 as well as the 1:1 complex could be observed in the Tc-99 NMR experiment, depending on the ligand to metal ratio. Complex 2 crystallizes in the monoclinic space group P2(1)/c, a = 14.79(2) Angstrom, b = 11.691(2) Angstrom, c = 16.94(2) Angstrom, beta = 94.88(6)degrees, Z = 8. The tripodal ligand is coordinated through the sulfur atoms to the metal center, forming three favorable five-membered chelate rings. Complex 3 crystallizes in the monoclinic space group C2/c, a = 26.073(4) Angstrom, b = 9.288(1) Angstrom, c 17.898(3) Angstrom, beta = 99.84(1)degrees, Z = 4. The binuclear unit is formed by two fac-[Tc(tosylate)(CO)3(]) moieties which are trans, bidentate coordinated to the macrocyclic ligand. Compound 5 crystallizes in the monoclinic space group Pc, a = 25.737(4) Angstrom, b = 14.009(1) Angstrom, c = 26.479(3) Angstrom, beta = 149.56(2)degrees, Z = 4. In the case of the dicationic compound 5, the two Tc(I) centers are tripodal, cis coordinated toward the thia crown ether. A detailed analysis of the ring conformation in the solid state structure explained to a certain extent the formation of only one isomer (trans in the case of 3 and cis in the case of 5, respectively) during the substitution reaction.