Structural and (99)Tc 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-S(3))(CO)(3)]Br, fac-[Tc(2)(tosylate)(2)(18-ane-S(6))(CO)(6)], and fac-[Tc(2)(20-ane-S(6)-OH)(CO)(6)][tosylate](2).

Abstract

Starting originally from the organometallic precursor [NEt(4)](2)[TcBr(3)(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 3,6,9,13,16,19-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, (1)H, (99)Tc 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 (99)Tc NMR experiment, depending on the ligand to metal ratio. Complex 2crystallizes in the monoclinic space group P2(1)/c, a = 14.79(2) Å, b = 11.691(2) Å, c = 16.94(2) Å, 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) Å, b = 9.288(1) Å, c = 17.898(3) Å, 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) Å, b = 14.009(1) Å, c = 26.479(3) Å, 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.