A stable silicon(0) compound with a Si=Si double bond

Dative, or nonoxidative, ligand coordination is common in transition metal complexes; however, this bonding motif is rare in compounds of main group elements in the formal oxidation state of zero. Here, we report that the potassium graphite reduction of the neutral hypervalent silicon-carbene complex L:SiCl4 {where L: is:C[N(2,6-Pri2-C6H3)CH]2 and Pri is isopropyl} produces L:(Cl)Si-Si(Cl):L, a carbene-stabilized bis-silylene, and L:Si=Si:L, a carbene-stabilized diatomic silicon molecule with the Si atoms in the formal oxidation state of zero. The Si-Si bond distance of 2.2294 +/- 0.0011 (standard deviation) angstroms in L:Si=Si:L is consistent with a Si=Si double bond. Complementary computational studies confirm the nature of the bonding in L:(Cl)Si-Si(Cl):L and L:Si=Si:L.     

Anglicisms in the German medical vocabulary

In view of an ever-increasing infiltration of the German medical vocabulary by Britishisms and Americanisms, a linguistic attempt was made to categorize this phraseology as follows: more or less incorporated terminology, "internationalized" terms, identical translations, unnecessary use of English expressions instead of German synonyms, borrowing from the English with an alteration of the original meaning, and German neologisms on the basis of English vocabular material. Specimens from all these categories are enumerated.     

Reefs and islands of the Chagos Archipelago,Indian Ocean: why it is the world's largest no‐take marine protected area

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Establishing tradable water rights: implementation of the Mexican water law

Mexico passed a new water law in 1992 that shifted from state-managed water policy to a regulated market-oriented policy with tradable water rights. Water trading will initially be closely supervised by government agencies, but the law includes a number of provisions that will allow liberalization of water markets as water users become more involved in operation and management of water and gain experience in water trading. Incentives for the Mexican water policy reforms include the growing economic value of increasingly scarce water; the rising budgetary costs from highly subsidized capital development and operations and maintenance for irrigation and water supply systems; and general liberalization of the Mexican economy, which has raised the cost of maintaining relatively inflexible water allocation systems that cannot respond to changing incentives.     

Planar hexacoordinate carbon: a viable possibility

The viability of molecules with planar hexacoordinate carbon atoms is demonstrated by density-functional theory (DFT) calculations for CB6(2-), a CB6H2 isomer, and three C3B4 minima. All of these species have six pi electrons and are aromatic. Although other C3B4 isomers are lower in energy, the activation barriers for the rearrangements of the three planar carbon C3B4 minima into more stable isomers are appreciable, and experimental observation should be possible. High-level ab initio calculations confirm the DFT results. The planar hexacoordination in these species does not violate the octet rule because six partial bonds to the central carbons are involved.     

A carbon-free sandwich complex [(P5)2Ti]2-

Reactions of highly reduced titanium complexes with white phosphorus, P4, at or below 25 degrees C yielded brown to deep red-brown salts of the first entirely inorganic metallocene, [(eta5-P5)2Ti](2-)(1). Like ferrocene and other carbon-based metallocenes, the structure of 1 has parallel and planar five-membered rings symmetrically positioned about the central metal atom. Despite its electron-deficient (16 electron) and formally zerovalent titanium character, salts of 1 are highly stable toward heat and air, both in solution and in the solid state. Computational studies show that the pentaphosphacyclopentadienyl unit, P5, functions as an unusually effective acceptor ligand, and this results in substantial stabilization of 1.     

Stomach contents of some shore-caught teleosts of Natal,South Africa

Stomach contents of shore-caught teleosts feeding on the Natal nearshore substratum were visually analysed for percentage composition. Commonly caught fish, namely Rhabdosargus sarta, R. holubi, Pomadasys commersonni, Trachinotus africanus and T. botta, were opportunistic omnivorous predators and fed largely on sand mussels and benthic crustacea. Less frequently caught predatory fish (15 species) fed mainly on benthic crustacea and other teleosts. The results are discussed briefly and will provide an input to a current ecosystem study on the environment in which these fish feed.