ChemInform Abstract: Conformations and Thermodynamic Properties of Sulfur Homocycles. Part 1. The S5, S6, S7, and S8 Molecules.

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La8Br7Ni4: ribbons of Ni hexagons in condensed La6 trigonal prisms

A ternary lanthanum bromide La 8Br 7Ni 4 was synthesized from La, LaBr 3, and Ni under an Ar atmosphere at 830 degrees C. It crystallizes in space group C2/ m (No. 12) with lattice constants a = 29.528(4) A, b = 4.0249(6), c = 8.708(1) A, and beta = 94.515(2) degrees . The structure features condensed Ni-centered La 6 trigonal prisms. The Ni atoms are bonded to each other to form ribbons of Ni hexagons. Band structure, bonding, and physical properties of the compound have been investigated.     

Total synthesis of (-)-(6S,7S,8S,9R,10S,2'S)-membrenone-A and (-)-(6S,7S,8S,9R,10S)- membrenone-B and structural assignment of membrenone-C

[reaction: see text] (-)-(6S,7S,8S,9R,10S,2'S)-Membrenone-A and (-)-(6S,7S,8S,9R,10S)-membrenone-B were prepared in 11 steps (3% and 2.4% overall yield, respectively). Key steps included a tin(II)-mediated aldol followed by a syn selective reduction, giving the C7-C9 stereocenters, a second chain extending aldol coupling, and a p-TsOH-promoted cyclization/dehydration giving the common gamma-dihydropyrone precursor. We have thus established that synthetic (-)-(6S,7S,8S,9R,10S,2'S)-membrenone-A, (-)-(6S,7S,8S,9R,10S)-membrenone-B, and (-)-(6S,7S,8S,9R,10S)-membrenone-C are the enantiomers of the natural products.     

Thermodynamic Characteristics of Ni3S2 Compound Formation

Published data on thermodynamic properties of the Ni₃S₂ compound in the liquid and solid states are compared and discussed.     

High nuclearity in azido/oximate chemistry: Ni14 and Ni13 clusters with S = 6 and 9 ground states

In the present work, we report a family of Ni(14) and unprecedented Ni(13) clusters linked by end-on azido and oximato bridges. Ferrimagnetic response gives S = 6 and 9 ground states, resulting in the largest nuclearities and spins in nickel oximato chemistry.     

Synthesis of 11-hydroxydrim-8(9)-en-7-one and 11,12-dihydroxydrim-8(9)-en-7-one from drim-8(9)-en-7-one

A synthetic route to 11-hydroxydrim-8(9)-en-7-one and 11,12-hydroxydrim-8(9)-en-7-one, valuable key intermediates for the preparation of naturally occurring biologically active drimanic sesquiterpenoids, starting from easily available drim-8(9)-en-7-one was developed. 11-Hydroxydrim-8(9)-en-7-one was obtained by peracidic oxidation of the enol acetate of drim-8(9)-en-7-one. 11,12-Dihydroxydrim-8(9)-en-7-one was synthesized from drim-8(9)-en-7-one by two routes, namely, by a five-step procedurevia 11-hydroxydrim-8(9)-en-7-one and by bromination of drim-8(9)-en-7-one with NBS to give 11,12-dibromodrim-8(9)-en-7-one followed by its acetoxylation and deacetylation. Deceased Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 95–98, January, 2000.     

Synthesis of 11-hydroxydrim-8(9)-en-7-one and 11,12-dihydroxydrim-8(9)-en-7-one from drim-8(9)-en-7-one

A synthetic route to 11-hydroxydrim-8(9)-en-7-one and 11,12-hydroxydrim-8(9)-en-7-one, valuable key intermediates for the preparation of naturally occurring biologically active drimanic sesquiterpenoids, starting from easily available drim-8(9)-en-7-one was developed. 11-Hydroxydrim-8(9)-en-7-one was obtained by peracidic oxidation of the enol acetate of drim-8(9)-en-7-one. 11,12-Dihydroxydrim-8(9)-en-7-one was synthesized from drim-8(9)-en-7-one by two routes, namely, by a five-step procedurevia 11-hydroxydrim-8(9)-en-7-one and by bromination of drim-8(9)-en-7-one with NBS to give 11,12-dibromodrim-8(9)-en-7-one followed by its acetoxylation and deacetylation. Deceased Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 95–98, January, 2000.     

Calculation of electron densities for EuI 4f 7(8 S)6s7s

Using the non-relativistic Hartree-Fock computer code of Froese Fischer, calculations have been performed for all terms of the configuration 4f ⁷(⁸ S)6s7s of EuI. The results are compared with recent isotope shift and hyperfine structure measurements. The calculated electron charge densities reproduce, up to a scaling factor, the experimental field shifts.     

Quasi-1D cations 1 infinity [Ni8Bi8S]n + of variable charge: infinite columns 1 infinity [Ni8Bi8S]2+ in the novel compound Ni8Bi8SI2

The new compound Ni(8)Bi(8)SI(2) has been synthesized and its crystal structure determined by X-ray crystallography. The structure contains one-dimensional (1D) cations (1)( infinity )[Ni(8)Bi(8)S](2+) separated by iodine anions. The geometry of the columns is similar to that of the recently reported (1)( infinity )[Ni(8)Bi(8)S](+), and the main difference between them is only their formal charge. Electronic structure calculations and physical properties measurements were performed to analyze the influence of the number of valence electrons on the bonding and properties of compounds containing these 1D cations. It was shown that the removal of one electron (i.e., (1)( infinity )[Ni(8)Bi(8)S](+) --> (1)( infinity )[Ni(8)Bi(8)S](2+)) mainly affects the Ni-S bonding within the cation and essentially has no influence on the intermetallic Ni-Bi bonding. It was found that Ni(8)Bi(8)SI(2) containing double-charged columns has conductivity properties more similar to a pure 1D metal than the congener Ni(8)Bi(8)SI containing mono-charged columns.     

Isomery of [Re6S6Br8] and [Re6S5Br9] Units in a Rhenium Cluster Thiobromide: Experimental and Theoretical Approaches

The rhenium cluster thiobromide Cs_1.95(1)Re₆S_5.82(3)Br_8.19(3), belonging to the solid solution Cs₂Re₆S₆Br₈–CsRe₆S₅Br₉, crystallizes in the trigonal system (P31c, a = 10.001(5) Å and c = 14.676(5) Å). It is built up from [Re₆L ₈ ⁱ ]Br ₆ ^a cluster units in which sulphur and bromine are randomly distributed on inner position (Lⁱ). From the structural refinement performed using single-crystal X-ray diffraction data, the isomers of the [Re₆Sⁱ ₆Br ₂ ⁱ ] and [Re₆S ₅ ⁱ Br ₃ ⁱ ] cluster cores present in the structure have been unambiguously determined, due to the non-centro symmetry of the structure. Density functional theory calculations have been performed for all possible di- and tri-substituted isomers in order to confirm experimental analyses. Slight differences between the stability of di-substituted and tri-substituted cluster unit isomers built from Mo₆ cluster and Re₆ clusters are evidenced.     

Systematic synthesis of heterometallic Ni/Fe/S and Cu/Fe/S clusters with a pentlandite-like M8S6 core

The systematic synthesis of heterometallic Ni/Fe/S and Cu/Fe/S clusters with a M8S6 core structure that resembles that of pentlandite minerals is described. The chemical properties and electronic structures of the new clusters have been investigated and are reported in this communication.