The structure of hexamethyltungsten, W(CH3)6, was determined by x-ray single-crystal diffraction at −163°C. The molecule has a strongly distorted trigonal prismatic structure with C3v symmetry. This irregular structure is not a result of intermolecular forces, but rather represents its true molecular structure. A similar structure, which deviates less from the ideal trigonal prismatic structure, was determined for hexamethylrhenium, Re(CH3)6. Although these structures violate the simplistic models used to predict the geometry of molecules, they are at least in part explainable by the molecular orbital model.

https://science.sciencemag.org/content/sci/271/5249/626.full.pdf

Crystal and Molecular Structures of Hexamethyltungsten and Hexamethylrhenium

The literature concerning cluster complexes which contain both main group element and transition metal vertices is reviewed. Synthetic methods and general reactivity patterns are summarized. Emphasis is placed on structural. Comparisons of cluster geometries for a wide variety of element combinations. Relationships between these mixed clusters and the main group element clusters known as Zintl ions are discussed.

The Interface of Main Group and Transition Metal Cluster Chemistry

https://meteoritegallery.com/wp-content/uploads/2014/04/Evidence-for-aqueous-activity-on-comet-81PWild-2-from-sulﬁde-mineral-assemblages-in-Stardust-samples-and-CI-chondrites.pdf

Evidence for aqueous activity on comet 81P/Wild 2 from sulfide mineral assemblages in Stardust samples and CI chondrites

http://zolotov.faculty.asu.edu/publ/Zolotov-fluids-2012.pdf

Aqueous fluid composition in CI chondritic materials: Chemical equilibrium assessments in closed systems

Publisher Summary This chapter discusses the chemistry of carbidocarbonyl clusters. The rapid expansion in carbidocarbonyl cluster chemistry has enabled the chemistry of these compounds to be addressed in its own right rather than as a subgroup of cluster chemistry as a whole. The first carbidocarbonyl transition metal cluster to be recognized was Fe 5 C(CO) 15 ,which was isolated in very low yield from the reaction of tri-iron dodecacarbonyl with methylphenylacetylene and characterized by X-ray diffraction by Dahl and coworkers. The lowest nuclearity carbidocarbonyl clusters of ruthenium and osmium are Ru 5 C(CO) 15 and Os 5 C(CO) 15 . The chemistry of the carbidocarbonyl clusters of cobalt and rhodium is predominantly the work of Italian school of the late Paolo Chini and colleagues. Pyrolysis of Et 4 N[ReH 2 (CO)] at 250°C in n-tetradecane yields a mixture of polynuclear products from which two carbidocarbonyl clusters of rhenium have been isolated. The application of spectroscopic techniques familiar in organometallic chemistry to the unique features of carbidocarbonyl clusters has become more evident since the previous review of this field. Since the completion of this review (mid 1982), the chemistry of carbidocarbonyl clusters has continued to expand rapidly.

The Chemistry of Carbidocarbonyl Clusters

We have used synchrotron Fe-XANES, XRS, micro Raman, and SEM-TEM analyses of Stardust track 41 slice and track 121 terminal area slices to identify Fe oxide (magnetite-hematite and amorphous oxide). Fe-Ti oxide, and V-rich chromite (Fe-Cr-V-Ti-Mn oxide) grains ranging in size from 200 nm to similar to ~10 μm. They co-exist with relict FeNi metal. Both Fe-XANES and microRaman analyses suggest that the FeNi metal and magnetite(Fe2O3FeO) also contain some hematite (Fe2O3). The FeNi has been partially oxidized (probably during capture), but on the basis of our experimental work with a light-gas gun and microRaman analyses, we believe that some of the magnetite-hematite mixtures may have originated on Wild 2. The terminal samples from track 121 also contain traces of sulfide and Mg-rich silicate minerals. Our results show an unequilibrated mixture of reduced and oxidized Fe-bearing minerals in the Wild 2 samples in an analogous way to mineral assemblages seen in carbonaceous chondrites and interplanetary dust particles. The samples contain some evidence for terrestrial contamination, for example, occasional Zn-bearing grains and amorphous Fe oxide in track 121 for which evidence of a cometary origin is lacking.

Iron oxides in comet 81P/Wild 2

The reactions between titanium(IV) chloride and tetra-alkylammonium chlorides and between titanium(IV) bromide and tetra-alkylammonium bromides, in solution in dichloromethane, have been studied by Raman and i.r. spectroscopy. The five-co-ordinate ions [TiCl5]– and [TiBr5]– have been clearly identified for the first time. These ions and the other singly charged species [Ti2Cl9]– and [Ti2Br9]– are the only anions detected by Raman spectroscopy in the dichloromethane solutions. The preparations of the tetrabutylammonium salts [Bu4N][TiCl5] and [Bu4N][TiBr5] and of tetraphenylarsonium pentachlorotitanate are described, but the corresponding salts of the smaller tetraethyl- and tetrapropyl-ammonium cations are shown to be [Et4N]2[Ti2Cl10], [Et4N]2[Ti2Br10], and [Pr4N]2[Ti2Cl10] with binuclear halogen-bridged anions.

Pentachloro- and pentabromo-titanate(IV) ions

5-Coordinate halogeno-complexes and related ions: Halogeno-complexes of Fe(III) and Ti(IV)

A simplified synthesis of the hexamethylplatinate(IV) ion

The metal–metal stretching region of the i.r. and Raman spectra of [Rh4(CO)12] is reported and analysed. The hitherto unpublished solution and 13CO-enriched spectra suggest that the metal–metal region should be reassigned, and these results are compared with those for [Ir4(CO)12].

J. Alan Creighton

Papers

Iron oxides in comet 81P/Wild 2

Pentachloro- and pentabromo-titanate(IV) ions

5-Coordinate halogeno-complexes and related ions: Halogeno-complexes of Fe(III) and Ti(IV)

A simplified synthesis of the hexamethylplatinate(IV) ion

A vibrational spectroscopic study of [Rh4(CO)12]