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The synthesis and crystal structures of two new rhenium(I) complexes obtained utilizing benzhydroxamic acid (BHAH) and 3-hydroxyflavone (2-phenylchromen-4-one, FlavH) as bidentate ligands, namely tetraethylammonium fac-(benzhydroxamato-κ 2 O,O')bromidotricarbonylrhenate(I), (C 8 H 20 N)[ReBr(C 7 H 6 NO 2 )(CO) 3 ], 1, and fac-aquatricarbonyl(4-oxo-2-phenylchromen-3-olato-κ 2 O,O')rhenium(I)-3-hydroxyflavone (1/1), [Re(C 15 H 9 O 3 )(CO) 3 (H 2 O)]·C 15 H 10 O 3 , 3, are reported. Furthermore, the crystal structure of free 3-hydroxyflavone, C 15 H 10 O 3 , 4, was redetermined at 100 K in order to compare the packing trends and solid-state NMR spectroscopy with that of the solvate flavone molecule in 3. The compounds were characterized in solution by 1 H and 13 C NMR spectroscopy, and in the solid state by 13 C NMR spectroscopy using the cross-polarization magic angle spinning (CP/MAS) technique. Compounds 1 and 3 both crystallize in the triclinic space group P-1 with one molecule in the asymmetric unit, while 4 crystallizes in the orthorhombic space group P2 1 2 1 2 1 . Molecules of 1 and 3 generate one-dimensional chains formed through intermolecular interactions. A comparison of the coordinated 3-hydroxyflavone ligand with the uncoordinated solvate molecule and free molecule 4 shows that the last two are virtually completely planar due to hydrogen-bonding interactions, as opposed to the former, which is able to rotate more freely. The differences between the solid- and solution-state 13 C NMR spectra of 3 and 4 are ascribed to inter- and intramolecular interactions. The study also investigated the potential labelling of both bidentate ligands with the corresponding fac- 99m Tc-tricarbonyl synthon. All attempts were unsuccessful and reasons for this are provided.

The title compound, C(7)H(10)F(6)O(4), was isolated as an unexpected product from a reaction of tantalum(V) methoxide with hexa-fluoro-acetyl-acetone in a methanol solution. The asymmetric unit consists of one half-mol-ecule with the middle C atom lying on a twofold axis. The crystal structure is stabilized by O-H⋯O and an array of C-H⋯F hydrogen-bonding inter-actions. These inter-actions link the mol-ecules into a stable supra-molecular three-dimensional network. The mol-ecules pack in a ribbon-like form in the ac plane as a result of these inter-actions.

In the title compound, [RhCl(C(21)H(21)P)(2)(CO)], the coordination geometry around the Rh(I) atom is slightly distorted square-planar with the phosphane ligands in trans positions with respect to each other. The chloride and carbonyl ligands show positional disorder, and the Rh(I) atom lies on a center of inversion. The effective cone angle Θ(E) for the title compound is 169.0 (3)°. There are no significant inter-molecular inter-actions.

In the title compound, [Nb(CH(3)O)(3)(C(5)H(7)O(2))Cl], the Nb(V) atom is coordinated by two O atoms from the chelating acetyl-acetonate ligand, three O atoms from the methano-late groups and one chloride ligand. The octa-hedral environment around niobium is slightly distorted with Nb-O distances in the range 1.8603 (15)-2.1083 (15) Å and an Nb-Cl distance of 2.4693 (9) Å. The O-Nb-O angles vary between 80.74 (6) and 100.82 (7)°, while the trans Cl-Nb-O angle is 167.60 (5)°. There are no hydrogen bonds observed, only an inter-molecular C-H⋯O inter-action.