A study has been carried out on rhodium catalyst preforming when modified with the bulky tris(2,4-di-tert-butylphenyl) phosphite, P(Obtbp)(3). X-Ray crystal structure determinations of a tropolone-type precursor complex [Rh(TropBr(3))(CO){P(Obtbp)(3)}].P(Obtbp)(3).CH(3)COCH(3)(TropBr(3)= 3,5,7-tribromotropolonate) and the free P(Obtbp)(3) ligand are reported. Systematic in situ IR and NMR studies of the particular rhodium phosphite modified catalyst and its precursors have led to the identification of two distinct rhodium hydride species. A {(1)H,(31)P} HMBC NMR experiment afforded clarity on the (31)P NMR spectra observed under hydroformylation conditions. The species were identified as [HRh(CO)(3){P(Obtbp)(3)}] and [HRh(CO)(2){P(Obtbp)(3)}(2)]. Attention was also given to the rate of catalyst formation when starting from different rhodium precursors.

The centrosymmetric title compound, [PdCl2(C19H17P)2], crystallizes with a square-planar geometry about the PdII metal centre. The most important bond distances include Pd—P (trans P) of 2.3404 (9) Å and Pd—Cl (trans Cl) of 2.2977 (12) Å. Weak intra- and intermolecular hydrogen bonding is observed in the solid-state structure between the chloro and phenyl H atoms. This weak intermolecular hydrogen-bonding pattern forms a one-dimensional chain along the b axis.

The title compound, [RhCl(C19H17P)2(CO)], can be characterized as a Vaska-type complex containing a diphenyl(4-tolyl)phosphine ligand. The rhodium(I) metal centre has a square-planar coordination. The molecule is disordered, with the Rh atom lying on an inversion centre. The most important bond lengths and angles include Rh—P = 2.3315 (9) Å, Rh—Cl(trans CO) = 2.405 (2) Å, Rh—C(carbonyl) = 1.724 (11) Å and Rh—C—O = 178.0 (6)°.

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-κ2 O,O′)bromidotricarbonylrhenate(I), (C8H20N)[ReBr(C7H6NO2)(CO)3], 1, and fac-aquatricarbonyl(4-oxo-2-phenylchromen-3-olato-κ2 O,O′)rhenium(I)–3-hydroxyflavone (1/1), [Re(C15H9O3)(CO)3(H2O)]·C15H10O3, 3, are reported. Furthermore, the crystal structure of free 3-hydroxyflavone, C15H10O3, 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 1H and 13C NMR spectroscopy, and in the solid state by 13C NMR spectroscopy using the cross-polarization magic angle spinning (CP/MAS) technique. Compounds 1 and 3 both crystallize in the triclinic space group P\overline{1} with one molecule in the asymmetric unit, while 4 crystallizes in the orthorhombic space group P212121. 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 13C 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-99mTc-tricarbonyl synthon. All attempts were unsuccessful and reasons for this are provided.

Key indicatorsSingle-crystal X-ray study T = 100 K Mean (C-C) = 0.002 Å Disorder in main residue R factor = 0.018 wR factor = 0.047 Data-to-parameter ratio = 19.5For details of how these key indicators were automatically derived from the article, see