A Tl-205 NMR study to probe the solution structure and dynamics of a series of thallium-containing metal complexes has been conducted. The following compounds were examined : Tl{Co(CO)(4)}(3) (Ia), [BnMe3N](3)[Tl{Fe(CO)(4)}(3)] ([BnMe3N](3)[Ib]), Tl{M(CO)(3)Cp}(3) (Ic, M = Cr; Id, M = Mo; Ie, M = W), TlFp(3) (If; Fp = CpFe(CO)(2)), [PPN](2)[Tl2Fe6(CO)(24)] ([PPN](2)[II]), [Et4N](2)[Tl2Fe4(CO)(16)] ([Et4N](2)[III]), [Et4N][L2Tl{Fe(CO)(4)}(2)] ([Et4N][IV] : [IVa](-), L-2 = bipy; [IVb](-), L-2 = en; [IVc](-), L-2 = phen; [IVd](-), L-2 = tmeda; [IVe](-), L-2 = dien), [Et4N](4)[Tl4Fe8(CO)(30)] ([Et4N](4)[V]), and TlCo(CO)(4) (VI). The Tl-205 NMR technique was used to probe the dynamic behavior of the Tl-metal cluster complexes [II](2-), [III](2-), and [V](4-) in solution and the formation of Lewis base adducts of [III](-), as well as the possibility of formation of carbonylate anion adducts of Ia, Ic, Id, and If. [IVb](-) reacted with acetone and formed, after fortuitous oxidation, [{(CO)(4)FeL2’Tl}(2)Fe(CO)(4)] (L-2’ = Me2C=NCH2CH2N=CMe2) (VII). The initially formed complex [L-2’Tl{Fe(CO)(4)}(2)](-) ([Et4N][IVf]) was spectroscopically characterized. Additionally, the two known but structurally uncharacterized complexes Ia and If as well as the new complexes [BnMe3N](3)[Ib] and VII were characterized by single-crystal X-ray diffraction. Compound Ia crystallizes in the monoclinic space group P2(1)/n with a = 16.855(3) Angstrom, b = 6.7790(10) Angstrom, c = 19.049(4) Angstrom, beta = 113.84(3)degrees, V = 1990.8(6) Angstrom(3), Z = 4, R-1(F) = 0.0221, and wR(2)(F-2) = 0.0542 [I > 2 sigma(I)]. Compound If was synthesized from K[Fp] and TlCl3 . 4H(2)O and crystallizes in the triclinic space group with a = 10.789(2) Angstrom, b = 14.239(3) Angstrom, c = 16.703(3) Angstrom, alpha = 69.39(3)degrees, beta = 89.50(3)degrees, gamma = 69.07(3)degrees, V = 2223.1(7) Angstrom(3), Z = 4, R-1(F) = 0.0350, and wR(2)(F-2) = 0.0877 [I > 2 sigma(I)]. Compound [BnMe3N](3)[Ib] was synthesized from Na2Fe(CO)(4) . 3/2diox and Tl(OAc)(3) in MeCN and crystallizes in the hexagonal space group P6(3)/m with a = 18.290(3) Angstrom, c = 8.479(2) Angstrom, V = 2456.4(8) Angstrom(3), Z = 2, R-1(F) = 0.0235, and wR(2)(F-2) = 0.0494 [I > 2 sigma(I)]. Compound VII crystallizes in the triclinic space group with a = 13.597(3) Angstrom, b = 15.040(3) Angstrom, c = 10.536(2) Angstrom, alpha = 92.75(3)degrees, beta = 95.07(3)degrees, gamma = 114.40(3)degrees, V = 1946.0(7) Angstrom(3), Z = 2, R-1(F) = 0.0461, and wR(2)(F-2) = 0.1295 [I > 2 sigma(I)].