Supramolecular recognition forces: an examination of weak metal-metal interactions in host-guest formation

Molecular receptors consisting of two parallel-disposed terpy-M-Cl units (M = Pd2+, Pt2+) are used to form host-guest adducts with aromatic molecules and with neutral square-planar Pt2+ complexes. Host-guest formation is controlled by several factors including pi-pi interactions and, in some cases, weak Pt-Pt interactions between the host and the guest. This latter interaction was examined by comparing the host-guest stability of adducts formed by isoelectronic Pt2+ and Au3+ complexes with the Pt2+ receptor. Consistently, the former is more stable.     

An investigation into the use of platinum ware for silicate analysis

The amount of platinum dissolved from platinum apparatus used for dissolving silicate materials to obtain solutions for analysis has been determined. The study included apparatus made from an alloy containing 95 % platinum and 5 % gold. The affinity of iron and platinum was investigated, together with the problem of removing iron from platinum after the latter has been contaminated during fusions. The behaviour of platinum in a classical scheme for the analysis of silicate materials was investigated and the distribution of the platinum in various precipitates established. Platinum has been found to interfere in commonly used methods for the determination of silica, aluminium, iron, titanium, calcium and magnesium.     

Insertion reactions of dimethylsilylene: relative reactivity towards oxygenz.sbnd;hydrogen,siliconhydrogen,and siliconz.sbnd;alkoxy bonds

Photochemically-generated dimethylsilylene is found in competition experiments to insert preferentially into oxygenhydrogen bonds of alcohols compared to either siliconhydrogen bonds of silanes or siliconoxygen bonds of alkoxysilanes. This selectivity for OH bonds compared to SiH bonds is quite high in tetrahydrofuran and in dilute hydrocarbon solutions. However, it decreases in more concentrated hydrocarbon solutions. These effects are discussed in terms of aggregation of alcohols, hydrogen bonding, and solvent-mediated dimethylsilylene reactivity.     

Structural studies of immobilized ethylenediamine as a preconcentrating agent for molybdate and tungstate

The structure of the complex formed between molybdate and the diamine functional group of N-β-aminoethyl-γ-aminopropylsilane (Dow Corning 2-6020) immobilized on a silica substrate is determined and compared with the analogous complex precipitated from solution. Infrared spectroscopy and photoacoustic spectroscopy were applied to establish the nature of the complex. The precipitate formed with ethylenediamine contains a polymeric molybdate species, whereas the molybdate retained by the immobilized ethylenediamine group is monomeric. Trace levels of tungstate and molybdate can be extracted from aqueous concentrated sodium chloride solutions on a column packed with controlled-pore glass beads treated with Z-6020.     

Synthesis and properties of 1-bromo-2,3,5,6-tetrakis(3-pentyl)benzene: a highly sterically hindered aryl bromide

The preparation of 1-bromo-2,3,5,6-tetrakis(3-pentyl)benzene is reported. The ¹H and ¹³C NMR spectra indicate the presence of rotational isomers at room temperature which interconvert on heating. Coalescence of the NMR peaks for the methine and methylene aliphatic protons is observed at 100–120 °C. The conversion of this aryl bromide to the corresponding aryllithium is reported. Similar but less bulky aryl bromides have also been synthesised.