A comparative study of the structures and reactivity of cyclometallated platinum compounds of N-benzylidenebenzylamines and cycloplatination of a primary amine

The reaction of cis-[PtCl(2)(dmso)2] with ligands 4-ClC(6)H(4)CHNCH(2)C(6)H(5) (1a) and 4-ClC(6)H(4)CHNCH(2)(4-ClC(6)H(4)) (1b) in the presence of sodium acetate and using either methanol or toluene as solvent produced the corresponding five-membered endo-metallacycles [PtCl{(4-ClC(6)H(3))CHNCH(2)C(6)H(5)}{SOMe(2)}] (2a) and [PtCl{(4-ClC(6)H(3))CHNCH(2)(4'-ClC(6)H(4))}{SOMe(2)}] (2b). An analogous reaction for ligands 2,6-Cl(2)C(6)H(3)CHNCH(2)C(6)H(5) (1c) and 2,6-Cl(2)C(6)H(3)CHNCH(2)(4-ClC(6)H(4)) (1d) produced five-membered exo-metallacycles [PtCl{(2,6-Cl(2)C(6)H(3))CHNCH(2)C(6)H(4)}{SOMe(2)}] (2c) and [PtCl{(2,6-Cl(2)C(6)H(3))CHNCH(2)(4'-ClC(6)H(3))}{SOMe(2)}] (2d) when the reaction was carried out in methanol and seven-membered endo-platinacycles [PtCl{(MeC(6)H(3))ClC(6)H(3)CHNCH(2)C(6)H(4)}{SOMe(2)}] (3c) and [PtCl{(MeC(6)H(3))ClC(6)H(3)CHNCH(2)(4'-ClC(6)H(3))}{SOMe(2)}] (3d) when toluene was used as a solvent. The reaction of 2,4,6-(CH(3))(3)C(6)H(2)CHNCH(2)(4-ClC(6)H(4)) (1e) produced in both solvents an exo-platinacycle [PtCl{(2,4,6-(CH(3))(3)C(6)H(2))CHNCH(2)(4'-ClC(6)H(3))}{SO(CH(3))(2)}] (2e). Cyclometallation of 4-chlorobenzylamine was also achieved to produce compound [PtCl{(4-ClC(6)H(3))CH(2)NH(2)}{SOMe(2)}] (2g). The reactions of endo- and exo-metallacycles with phosphines evidenced the higher lability of the Pt-N bond in exo-metallacycles while a comparative analysis of the crystal structures points out a certain degree of aromaticity in the endo-metallacycle.     

Origin of the magnetic bistability in molecule-based magnets: a first-principles bottom-up study of the TTTA crystal

The magnetic bistability present in some molecule-based magnets is investigated theoretically at the microscopic level using the purely organic system TTTA (1,3,5-trithia-2,4,6-triazapentalenyl). The TTTA crystal is selected for being one of the best-studied molecule-based systems presenting magnetic bistability. The magnetic properties of the high- and low-temperature structures (HT and LT phases, respectively) are accurately characterized by performing a First-Principles Bottom-Up study of each phase. The changes that the magnetic exchange coupling constants (J(AB)) undergo when the temperature is raised (LT → HT) or lowered (HT → LT) are also fully explored in order to unravel the reasons behind the presence of these two different pathways. The triclinic LT phase is diamagnetic due to the fact that the nearly eclipsed π dimer is effectively magnetically silent and not to formation of a covalent bond between two TTTA molecules. It is also shown that bistability in TTTA results from the coexistence of the monoclinic HT and triclinic LT phases in the temperature range studied.     

Directed assembly of nanoscale Co(ii)-substituted {Co(9)[P(2)W(15)](3)} and {Co(14)[P(2)W(15)](4)} polyoxometalates

Herein we report two structurally intriguing Co(ii)-substituted polyoxometalates, a {Co(9)[P(2)W(15)](3)} and {Co(14)[P(2)W(15)](4)} (compounds 1 and 2) that are formed from the same building blocks under subtly different conditions. Compound 1 displays a structure previously predicted but never before realised, whilst compound 2 is the first Co-containing Dawson-based single-molecule magnet and has a unique cruciform structure.     

Structure and bonding of ethoxy species adsorbed on transition metal surfaces

The interaction of the ethoxy radical with Cu(111), Ag(111), Pd(111) and Au(111) has been studied using a periodic density functional approach. The most stable adsorption site is the fcc with adsorption energies in the 1.1–2.2 eV interval. All analyses consistently indicate that ethoxy becomes negatively charged, that the presence of ethoxy slightly perturbs the electronic structure of the metallic surface, that the interaction is essentially of electrostatic character and not directional predicting a rather mobile species. The calculated adsorption energies are found to correlate almost linearly with the total net charge on the ethoxy moiety thus confirming that the electrostatic interactions dominate the bonding between this organic species and the underlying metallic surfaces.     

Identification of triterpenoid compounds of Centella asiatica by thin-layer chromatography and mass spectrometry

The identification of the four principal triterpenoid components of Centella asiatica has been achieved by TLC on silica gel plates and mass spectrometry, as a modification of the method described in the European Pharmacopoeia (5th edn). A combination of ethyl acetate and methanol as the mobile phase was found to be successful in separating these compounds from the rest of the main components of the extract. The spots were detected with anisaldehyde solution. The separated compounds were confirmed by MALDI -TOF mass spectrometry.     

Synthesis and structure of an unexpected platinum pi complex formed from substituted 1,4-diamino ligands through an elimination process

An unusual reactivity of cis-1,2-bis[(N,N-dimethylamino)methyl] cyclohexane with PtCl(2) was observed, resulting in the formation of a platinum(II) pi-olefin complex instead of the conventional square-planar cis Pt(II) coordination complex with the diamino ligand. This behavior was interpreted on the basis of the steric hindrance of the dimethylamino groups whose electron lone pairs are barely accessible to a platinum atom, which can make it difficult for both dimethylamino groups to bind platinum at the same time. This complex has been physically and spectroscopically characterized and its structure has been confirmed by using X-ray diffraction analyses on single crystals.     

Synthesis of novel palladium OCN-pincer complexes: unprecedented sequential C(sp3)-H activation and aerobic oxidation in the reaction of N,N-dialkyl-3-[(N,N-dimethylamino)methyl]-2-iodoanilines with Pd2(dba)3

The reaction of N,N-dialkyl-3-[(N,N-dimethylamino)methyl]-2-iodoanilines with Pd2(dba)3 under O2 gives palladium OCN-pincer complexes by means of an unprecedented process that involves the formal aerobic oxidation of C(sp3)-H bonds at the alpha position of the aniline N atom.