Structures of rhenium(I) complexes with 3-hydroxyflavone and benzhydroxamic acid as O,O'-bidentate ligands and confirmation of π-stacking by solid-state NMR spectroscopy.

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-κO,O')bromidotricarbonylrhenate(I), (CHN)[ReBr(CHNO)(CO)], 1, and fac-aquatricarbonyl(4-oxo-2-phenylchromen-3-olato-κO,O')rhenium(I)-3-hydroxyflavone (1/1), [Re(CHO)(CO)(HO)]·CHO, 3, are reported. Furthermore, the crystal structure of free 3-hydroxyflavone, CHO, 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 H and C NMR spectroscopy, and in the solid state by C NMR spectroscopy using the cross-polarization magic angle spinning (CP/MAS) technique.

1,1,1,5,5,5-Hexafluoro-2,4-dimeth-oxy-pentane-2,4-diol.

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.

trans-Carbonyl-chloridobis(tri-o-tolyl-phosphane-κP)rhodium(I).

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.

(Acetyl-acetonato-κO,O')chlorido-trimethano-latoniobium(V).

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.