Paul S. Braterman

Heteronuclear transition metal complexes : II. Chelating diphosphine and diarsine palladium and platinum di-μ-organothiotetracarbonyls of group VI, L—LM′(SR)2M(CO)4☆

Abstract Members of the series L—LM′(SR) 2 M(CO) 4 [L—L=1,2 bis(diphenylphosphino)ethane, o -phenylenebis(diethylarsine); M′=Pd, Pt; R=Me, Ph; M=Cr, Mo, W] have been prepared by ligand replacement reactions. The complexes, although highly stable as solids, decompose rapidly in solution. From their IR and diffuse reflectance elecrronic spectra there is evidence that the complexes L—LM′(SR) 2 behave simply as chelating disuophide ligands; in contrast to the complexes (π-C 5 H 5 ) 2 Ti(SR) 2 M(CO) 4 1 there is no evidence for any metalmetal bonding.

Magnesium hydroxide precipitation as studied by gel growth methods

Abstract The precipitation of magnesium hydroxide from aqueous solutions by reaction with calcium hydroxide has been studied in agarose gel by electron microscopy and diffraction. The first stage, which dominates at very low Mg 2+ concentrations, is the formation of thin single crystals of magnesium hydroxide, some 500 nm or less in diameter. At higher concentrations, these are overgrown to produce larger particles, thicker towards the outside, and generally consisting of several crystallites, with a common c -axis, but imperfectly aligned in the ab plane. The implications for growth mechanisms, and for the production of magnesium hydroxide from seawater, are discussed.

Photoisomerism and steric stability in a five-coordinate photolytic fragment, MO(CO)4 P(C6 H11)3

Summary MO(CO)4 PCx3 (Cx = cyclohexyl), generated by photolysis of Mo(CO)5PCx3 in hydrocarbon glass, exists as two isomers with the phosphine and the vacancy in the coordination octahedron mutually cis and trans and the trans isomer may be converted into cis, using visible light, by a truly photochemical, non-thermal process.

Photoprecipitation and the banded iron-formations — Some quantitative aspects

The oxidative deposition of iron in the Banded iron-Formations can be quantitatively accounted for by direct abiotic photo-oxidation, by extrapolating from laboratory conditions and making reasonable assumptions about the early Earth and its oceans. Within this model, iron supply was the limiting factor, the Precambrian ocean surfaces were iron-depleted, and hydrogen would have been released into the atmosphere at a rate controlled by Fe(II) mixing. Other mechanisms operating in parallel are not excluded, and the Fe(II) budget suggests that recirculation by reaction with reduced carbon was important by ca. 2.5 b.y.b.p.

Photolytic generation of Fe(CO)4MeTHF, Fe(CO)3(MeTHF)2, (2 isomers), and Fe(CO)4NEt3; Relevance to reactions of Fe2(CO)9

The title compounds have been prepared from Fe(CO)5 by glassy matrix photolysis; there is evidence for pre-photolytic ligand Fe(CO)5 interaction.

Strong interactions between [Co(CO)4]− and Li+ or Na+ in diethyl ether; the system LiBr/Co2(CO)3/diethyl ether

Summary Infrared spectra show [Co(CO) 4 ] − to be strongly distorted by Na + and especially Li + in dry diethyl ether. Lithium bromide with dicobalt octacarbonyl in dry diethyl ether gives Li + [Co 3 (CO) 10 ] − and Li + [Co(CO) 4 ] − .

Combining two or more techniques: Gel growth, gel feedstock, and precipitation from homogeneous solution

Abstract By combining the technique of gel growth with that of homogeneous precipitation, it is possible to study the morphology of inorganic precipitates with minimum disturbance by bulk diffusion or aggregation.

Direct observation of hydrated electrons in the u.v. photo-oxidation of [Fe(H2O)6]2+

Hydrated electrons are involved as intermediates in the photo-oxidation of [Fe(H2O)6]2+ to FeIII species in water at 265 nm.

Some observations on the systems Co2(CO)8/sodium amalgam and Hg[Co(CO)4]2/sodium amalgam, and the effect of added LiBr

Co2(CO)8 and Hg[Co(CO)4]2 react sodium amalgam and/or mercury in ethereal solvents to give a variety of products. On treatment with aqueous M(o-phen)3Cl2(M  Fe, Ni), the anions [Co(CO)4−, [Co3(CO)10]−, {Hg[Co(CO)4]3}− and {Hg[Co(CO)4]2Cl}− could be isolated as their [M(o-phen)3]2+ salts. The effect of LiBr on the reacting systems was also investigated and the anion {Hg[Co(CO)4]2Br}− isolated.

An Electron Microscopy Study of the Alkaline Hydrolysis Products of Tetraethoxysilane

The hydrolysis of tetraethoxysilane was studied in an ethanol-water system with ammonium hydroxide catalyst. Reactions were carried out with water concentrations of 5M and 10M and ammonia concentrations up to 1.7M, and the products examined by electron optical methods. Variation of reagent concentrations lead to changes in the product morphology from small irregular particles, through roughly spherical and spherical particles to large fused particles. Within the range of particulate material the variations in size can be related to the effect of reagent concentrations by consideration of the reactions occurring. The effect on morphology of replacing ammonia with ethylamine was investigated and resembles that of the use of much higher ammonia concentrations.