Synthesis, X-ray structure and electrochemical characterization of palladium(II) bearing ferrocenyldiphenylphosphine complexes

Four new complexes, [PdX(κ2-2-C6R4PPh2)(PPh2Fc)] [X = Br, R = H (1), R = F (2); X = I, R = H (3), R = F (4)], containing ferrocenyldiphenylphosphine (PPh2Fc) have been prepared and fully characterised. The X-ray structures of complexes trans-1, cis-2 and cis-4, and that of a decomposition product of 4, [Pd(κ2-2-C6F4PPh2)(μ-I)(μ-2-C6F4PPh2)PdI(PPh2Fc)] (5), have been determined. These complexes show a distorted square planar geometry about the metal atom, the bite angles of the chelate ligands being about 69°, as expected. The cis/trans ratio of 1–4 in solution is strongly dependent on solvent. The new complexes and the uncoordinated PPh2Fc ligand were electrochemically characterised by cyclic and rotating disk voltammetry, UV-visible spectroelectrochemistry, and bulk electrolysis in dichloromethane and acetonitrile. In both cases, oxidation occurs at both the ferrocene and phosphine centres, but the complexes oxidise at more positive potentials than uncoordinated PPh2Fc; subsequently, the metal–phosphorus bond is cleaved, leading to free PPh2Fc+, which undergoes further chemical and electrochemical reactions.

Prevalence of the thioamide {···H-N-C=S}2 synthon-solid-state (X-ray crystallography), solution (NMR) and gas-phase (theoretical) structures of O-methyl-N-aryl-thiocarbamides

Structural investigations, i.e. solid-state (X-ray), solution (¹H NMR) and gas-phase (theoretical), on molecules with the general formula MeOC(S)N(H)C₆H₄-4-Y: Y = H (1), NO₂ (2), C(O)Me (3), Cl (4) have shown a general preference for the adoption of an E-conformation about the central C–N bond. Such a conformation allows for the formation of a dimeric hydrogen-bonded {H–N–C=S}₂ synthon as the building block. In the cases of 1–3, additional C–H^...O interactions give rise to the formation of tapes of varying topology. A theoretical analysis shows that the preference for the E-conformation is about the same as the crystal packing stabilisation energy and consistent with this, the compound with Y = C(O)OMe, (5), adopts a Z-conformation in the solid-state that facilitates the formation of N–H^...O, C–H^...O and C–H^...S interactions, leading to a layer structure. Global crystal packing considerations are shown to be imperative in dictating the conformational form of molecules 1–5.

X-ray crystallography : applications in the biotechnology research

X-ray crystallography is essentially a form of very high resolution microscopy. It enables us to visualize protein structures at the atomic level and enhances our understanding of protein function. Specifically we can study how proteins interact with other molecules, how they undergo conformational changes, and how they perform catalysis in the case of enzymes. Armed with this information we can design novel drugs that target a particular protein, or rationally engineer an enzyme for a specific industrial process.