Molekülsruktur und abs. konfiguration von (+)-p-menthadien-(1,8)-on-(2)-rhodium(I)-h5-cyclopentadienid, (+)-(4S-Carvon) RhI(C5H5)

The title compound crystallizes in the orthorhombic space group P2₁2₁2₁ with 4 molecules in the unit cell (cell dimensions: a 9.778(2), b 10.639(2) and c 12.423(4) Å). The structure was solved by means of the heavy atom method. The rhodium atom is linked to both olefinic double bonds. The terpene carbonyl group does not participate in coordination to rhodium. Unlike the endocyclic olefinic group, which is approximately perpendicular to the coordination plane of rhodium, the exocyclic Cz.sbnd;C double bound shows a considerable deviation from this arrangement. The π-complexation of carvone with rhodium proceeds diastereospecifically. The absolute configuration of (+)-carvone is 4S in agreement with the assignment derived by indirect chemical correlation.     

Vinylidene complexes of transition metals : II. A new method of synthesis of vinylidene complexes. Cymantrene derivatives containing phenylvinylidene ligands

A rearrangement of transition metal acetylenic π-complexes into compounds with vinylidene n-ligands has been established. Compounds CpMn(CCHPh)-(CO)₂ and Cp₂Mn₂(μ-CCHPh)(CO)₄ with terminal and bridging phenylvinylidene (benzylidenecarbene) ligands respectively were obtained from the π-complexes CpMn(CO)₂(PhCCR) where R  H, Ph₃Ge or Ph₃Sn. Reactions leading to conversion of the terminal CCHPh group into a bridging ligand and vice versa were studied. Under the action of L  Ph₃P, (EtO)₃P or (PhO)₃P, substitution of CO groups in vinylidene complexes takes place and compounds CpMn(CCHPh)-(CO)L are formed. IR, ¹H and ¹³C NMR spectra of the novel complexes are discussed. The data obtained indicate an electron-withdrawing property of the CCHPh ligand and stronger bonding of this ligand to the metal as compared with a CO group.     

A new solid-phase polymerization—metal phthalocyanine sheet polymers

The thermal reactions of pure metal(11) 4,4′,4″,4′″-phthalocyanine-tetracarboxylic acids of copper, cobalt, and nickel at 350–400°C in vacuum have been studied using Fourier transform infrared spectrometry, gas chromatography, and mass spectrometry. Based on these observations, novel in situ reactions for the synthesis of heat-resistant phthalocyanine “sheet” polymers are described. The poly(metal phthalocyanine) polymers of copper, cobalt, and nickel so synthesized have been characterized by elemental analysis, infrared spectroscopy, and dynamic thermogravimetric analysis. The most noteworthy property of these polymers is their extreme resistance to heat in an anaerobic atmosphere and their high char yields (89–93%) at 800°C in a nitrogen atmosphere.     

Diffusion-controlled vinyl polymerization. I. The gel effect

It is well known that the reaction rate and molecular weight of vinyl polymers can change markedly during the course of polymerization and that these changes are due to the influence of diffusion on the termination reaction. The chain length dependence of the termination rate constant has been considered in this work and has resulted in a general method of treating the polymerization kinetics and molecular weight distribution. This method is independent of the form of the chain length dependency and is capable of dealing with both disproportionation and recombination modes of termination. A specific model for the termination rate constant with chain length dependence is proposed and is based on free volume theory and entanglement coupling. Master curves for the characteristics of the reaction rate and molecular weight distribution are presented with the application of this model.     

Double-layer effects on simple electrode reactions III. The reduction of Eu3+ and Cr3+ in the presence of thiocyanate anions. Evidence for ligand bridging

The rates of reduction of Eu³⁺ and Cr³⁺ have been measured in mixed perchlorate + thiocyanate electrolytes at constant ionic strength, using low concentrations of thiocyanate to minimize its association with the cationic reactants. The effect of adsorbed thiocyanate anions on the reduction kinetics of Cr³⁺ resembled those produced by iodide and bromide on both Cr³⁺ and Eu³⁺. However, thiocyanate exhibited an unusual catalytic effect on the reduction of Eu³⁺ which was identified as arising from a reaction pathway involving thiocyanate-bridging between the mercury surface and the Eu³⁺. The diagnostic criteria used to support the proposed mechanism included analysis of the rate—potential behavior and of the effects of competitively adsorbed iodide ions upon the reduction rates.     

Comparison of the structural and chemical composition of giant T-even phage heads.

A study has been made of the structure of the capsids of T4D giant phage produced from mutants in gene 23 and temperature-sensitive mutants in gene 24, and T4D and T2L giant phage formed by the addition of L-canavanine followed by an Larginine chase in the growth medium. All the giant phage capsids have been shown to be built according to the same geometrical architecture. This consists of a near-hexagonal surface net, lattice constant 129.5 A, folded into a left-handed T = 13 prolate icosahedron elongated along one of its fivefold symmetry axes. Their only apparent difference from wild-type T-even phage capsids is their abnormally elongated tubular part. A comparison of the capsomere morphologies and protein compositions of the giant phage capsids showed that all T4D giants are identical but differ from T2L: The T4D capsomere has a complex (6 + 6 + 1)-type morphology, whereas the T2L has a simple 6-type. T2L phage, however, lack two capsid proteins, "soc" and "hoc", present in T4D. The difference in capsomere morphology can therefore be related to the difference in the protein compositions of these two phage. Possible differences between the initiation and means of length regulation of giant phage heads and the aberrant polyheads are discussed.     

Etude de la chloration du polychlorure de vinyle en fonction de sa tacticite

Polyvinyl chloride samples of various tacticity have been prepared and photochlorinated in CCl₄ for 4 hr. The chlorination degree correlates directly with the degree of syndiotacticity. Initial PVC with syndiotacticity about 56 per cent, which can be regarded as alternate sequences of syndiotactic and isotactic diads, is quickly chlorinated. The mechanism of chlorine attack on the macromolecula is directly connected with the stereoregularity.     

Spectrophotometric determination of germanium with Catechol Violet and cetyltrimethylammonium bromide

A ternary complex between germanium, Catechol Violet (CV) and cetyltrimethylanunoniuni bromide is proposed for the determination of germanium. The stoichiometric ratio Ge:CV is 1:2. Beer's law is obeyed from 0.1 to 1.0 ppm of Ge. The method is highly selective. Interference from Sn(IV), Fe(III), Bi(III), Cr(VI), Mo(VI), V(V) and Sb(III) in mg amounts is eliminated by extracting the germanium into carbon tetrachloride from 9M HC1 and then stripping into water before the photometric determination.     

Cyclobutane polymers from acrylonitrile dimer

A wide variety of polyesters and polyamides was prepared from 1,2- and 1,3-disubstituted cyclobutane derivatives. In general, polyamides containing the trans-disubstituted cyclobutane ring were crystalline. Polyesters containing predominantly the trans-isomer tended to be crystalline but those containing mixtures of cis-trans isomers were amorphous. Mechanical properties have been determined wherever possible. Appreciable yields of cyclic dimers were isolated during the preparation of certain polyesters. These cyclic dimers readily polymerized when treated with dibutylzinc. Examination of acrylonitrile dimer (1,2-dicyanocyclobutane) by gas chromatography failed to reveal the presence of any 1,3-dicyanocyclobutanes.