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Hexacarbonyltechnetium(I) cation undergoes rapid hydrolysis in aqueous solutions at pH ≥ 7 with the formation of an unidentified carbonyl compound or mixture of compounds in the form of a pale yellow precipitate. Two crystalline fractions were isolated in the course of vacuum sublimation of the precipitate and were identified by single crystal X-ray diffraction as Tc2(CO)10 and Tc3H3(CO)12. The crystal and molecular structures of these compounds were described. The mechanism of their formation in the course of hydrolysis of [Tc(CO)6]+ cation is discussed.

The crystal and molecular structure of cesium tris(pivaloyltrifluoroacetonato)uranylate prepared in the form of a crystal solvate Cs[UO2(Bu t COCHCOCF3)3]·1.5C6H6·H2O was studied by single crystal X-ray diffraction. The compound crystallizes in the monoclinic system, a = 26.9099(9), b = 13.1549(4), c = 24.4586(8) A, β = 90.418(2)°, V = 8658.0(5) A3 (at 100 K), Z = 8, space group C2/c. Of the three β-diketonate ligands, two are coordinated to the uranyl ion in the bidentate fashion, and the third ligand, in the monodentate fashion, so that the equatorial coordination number of the uranyl ion is 5. The crystal structure is built of sandwich-type dimers in which two cesium cations are arranged between two tris(pivaloyltrifluoroacetonato)uranylate anions. The coordination sphere of the cesium cation is built of oxygen atoms of the β-diketone and uranyl groups, fluorine atom of the CF3 group, and π-coordinated benzene molecule. In addition, 0.5 benzene molecule and one water molecule (per formula unit) occupy structural voids.

The crystal and molecular structures of tricarbonyltechnetium acetylacetonate and its adduct with diethylamine were studied by single crystal X-ray diffraction. Tricarbonyltechnetium acetylacetonate crystallizes in the triclinic system, space group \( P\bar 1 \), a = 8.1154(1), b = 8.1961(2), c = 8.2695(1) A, α = 64.5618(9)°, β = 69.7899(8)°, γ = 83.6925(9)°, V = 465.652(14) A3 (at 100 K); Z = 2. The adduct also crystallizes in the triclinic system, space group P{ie145-2}, a = 7.9338(3), b = 8.5421(3), c = 12.1506(7) A, α = 96.961(3)°, β = 99.952(3)°, γ = 112.001(2)°, V = 736.25(6) A3 (at 100 K); Z = 2. Tricarbonyltechnetium acetylacetonate has a centrosymmetrical dimeric structure. The dimerization occurs through the formation of a bridging bond with the methine carbon atom of the acetylacetonate ligand which is thus coordinated in the tridentate chelating-bridging fashion. The adduct has a monomeric structure with chelating coordination of the acetylacetonate ligand and coordination of diethylamine to the technetium atom via N atom. In both complexes, the carbonyl groups are in the fac position. Differences between the structures of tricarbonyltechnetium acetylacetonate in the crystal and in solution are discussed.

Crystal and molecular structures of adducts of uranyl pivaloyltrifluoroacetonate with hexamethylphosphoramide [UO2(PTFA)2(HMPA)] (I) and of uranyl trifluoroacetylacetonate with trimethyl phosphate [UO2(TFA)2(TMP)] (II) were determined. Compound I crystallizes in the monoclinic system, space group P21/n; a = 16.9384(3), b = 9.1090(2), c = 20.9844(4) A, β = 101.5337(10)°, V = 3172.34(11) A3 (at 100 K); Z = 4. Compound II crystallizes in the rhombic system, space group Pbca; a = 17.8214(4), b = 7.7786(2), c = 30.9176(7) A, V = 4285.97(18) A3 (at 100 K); Z = 8. In both cases, the cis isomer in which the neutral ligand is located between the trifluoromethyl groups is realized. Compound I differing from II by the stronger branching of ligand periphery is characterized by stronger structural deformations in the crystal.

The crystal and molecular structure of uranyl acetylacetonate dimer was determined by single crystal X-ray diffraction. The compound crystallizes in the tetragonal system, a = 7.9420(2), c = 40.1240(13) A (at 100 K), Z = 4, space group P41212. Dimeric uranyl acetylacetonate molecules in the crystal are formed by bridging bonding of one of O atoms of the acetylacetonate ligands with U atoms, so that the coordination polyhedra of U atoms (distorted pentagonal bipyramids) share a common equatorial edge. The dimer has a nonplanar structure, being significantly bent along the conventional line connecting the bridging O atoms.

The crystal and molecular structures of [TcCl(CO)5] and [TcBr(CO)5] were determined. The compounds crystallize in the rhombic system, space group Pnma; a = 11.6757(18) and 11.9564(18) A, b = 11.7365(14) and 11.7250(18) A, c = 6.0407(7) and 6.2020(15) A, V = 827.77(19) and 869.5(3) A3, respectively; Z = 4. The structural data for pentacarbonyl halides were compared in the series Mn-Tc-Re and Cl-Br-I. Quantum-chemical calculations of the compounds [TcX(CO)5] (X = F, Cl, Br, I) and of the anion [TcCl3(CO)3]2− were made. A correlation between the geometry, electronic structure, and reactivity of the complexes is considered.