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Triene 6π electrocyclization, wherein a conjugated triene undergoes a concerted stereospecific cycloisomerization to a cyclohexadiene, is a reaction of great historical and practical significance. In order to circumvent limitations imposed by the normally harsh reaction conditions, chemists have long sought to develop catalytic variants based upon the activating power of metal-alkene coordination. Herein, we demonstrate the first successful implementation of such a strategy by utilizing [(C5 H5 )Ru(NCMe)3 ]PF6 as a precatalyst for the disrotatory 6π electrocyclization of highly substituted trienes that are resistant to thermal cyclization. Mechanistic and computational studies implicate hexahapto transition-metal coordination as responsible for lowering the energetic barrier to ring closure. This work establishes a foundation for the development of new catalysts for stereoselective electrocyclizations.

Relative to other cyclic poly-phosphorus species (that is, cyclo-Pn ), the planar cyclo-P4 group is unique in its requirement of two additional electrons to achieve aromaticity. These electrons are supplied from one or more metal centers. However, the degree of charge transfer is dependent on the nature of the metal fragment. Unique examples of dianionic mononuclear η4 -P4 complexes are presented that can be viewed as the simple coordination of the [cyclo-P4 ]2- dianion to a neutral metal fragment. Treatment of the neutral, molybdenum cyclo-P4 complexes Mo(η4 -P4 )I2 (CO)(CNArDipp2 )2 and Mo(η4 -P4 )(CO)2 (CNArDipp2 )2 with KC8 produces the dianionic, three-legged piano stool complexes, [Mo(η4 -P4 )(CO)(CNArDipp2 )2 ]2- and [Mo(η4 -P4 )(CO)2 (CNArDipp2 )]2- , respectively. Structural, spectroscopic, and computational studies reveal a similarity to the classic η6 -benzene complex (η6 -C6 H6 )Mo(CO)3 regarding the metal-center valence state and electronic population of the planar-cyclic ligand π system.

Elemental white phosphorus (P4 ) is well recognized as a critical precursor to organophosphorus compounds. However, regulatory constraints stemming from the toxic and pyrophoric nature of white phosphorus have significantly limited its accessibility. Herein is described a new approach to white phosphorus storage and release based on a unique example of photolytic reductive elimination of the tetrahedral P4 molecule from a mononuclear cyclo-P4 molybdenum complex. The latter functions as an air-stable, chemically-deactivated source of white phosphorus. The system features efficient photo-release of white phosphorus using inexpensive violet LED sources. Additionally, high-yield recapture of unspent white phosphorus by the molybdenum center can be achieved by post-photolysis heating at convenient temperatures.

The encumbered tetraisocyanide dianion Na2 [Fe(CNArMes2 )4 ] reacts with two molecules of CO2 to effect reductive disproportionation to CO and carbonate ([CO3 ]2- ). When the reaction is performed in the presence of silyl triflates, reductive disproportionation is arrested by silylative esterification of a mono-CO2 adduct. This results in the formation of four-coordinate terminal iron carbynes possessing an aryl carbamate substituent owing to the direct attachment of an C(O)OSiR3 group to an isocyanide nitrogen atom. Crystallographic, spectroscopic, and computational analyses of these iron-carbon multiply bonded species reveal electronic structure properties indicative of a conformationally locked iron carbyne unit.

The functionalized catecholate, tetraethyl (2,3-dihy- droxy-1,4-phenylene)bis(phosphonate) (H2-DPC), has been used to prepare a series of lithium salts Li(B(DPC)(oxalato)), Li(B(DPC)2), Li(B(DPC)F2), and Li(P(DPC)3). The phos- phoryl-rich character of these anions was designed to impart flame-retardant properties for their use as potential flame- retardant ions (FRIONs), additives, or replacements for other lithium salts for safer lithium-ion batteries. The new materials were fully characterized, and the single-crystal structures of Li(B(DPC)(oxalato)) and Li(P(DPC)3) have been deter- mined. Thermogravimetric analysis of the four lithium salts show that they are thermally stable up to around 2008C. Pyrolysis combustion flow calorimetry reveals that these salts produce high char yields upon combustion. Lithium-ion batteries (LIBs) have become the battery of choice for portable electronics and mobile communication devices because of their high energy density and their lack of a memory effect. As their size scales towards transportation applications there have been concerns surrounding their safety in light of an increasing number of well-publicized battery fires. High energy density LIBs present unique challenges, for a fully charged battery contains reactive and hazardous materials in the presence of flammable organic solvents. Catastrophic failures of a lithium-ion battery often include thermal runaway combined with fire and toxic fumes. It is thus unsurprising that a number of strategies are actively being pursued to manage the risks associated with LIBs. (1) One of the primary components of LIBs is the electrolyte, which in most commercial LIBs is a solution of LiPF6 in mixtures of organic carbonates, including ethylene carbonate, dimethyl carbonate, and diethyl carbonate. (2, 3) Of note is the novel salt lithium bis(oxalato)borate (LiBOB), (4) which has been shown to improve certain aspects of the solid electrolyte

Eine Acyl-Radikalcyclisierung zur Bildung des bicyclischen Gerustes von (−)-Kumausallen 1 war der Schlusselschritt in dessen 14stufiger, enantioselektiver Synthese. Es zeigte sich, das die Bromalleneinheit robust genug ist, um in einer Vielzahl von Syntheseschritten den Reaktionsbedingungen standzuhalten. Die absolute Konfiguration der Bromalleneinheit konnte durch diese Synthese zweifelsfrei bestatigt werden.

Ein Disauerstoffaddukt ist das spektroskopisch beobachtbare Intermediat bei der Reaktion des koordinativ ungesattigten Chromphenylkomplexes 1 mit O2 [Gl. (1)]. Durch intramolekulare Insertion von O2 in die Cr-C(Ph)-Bindung wird der Titelkomplex 2 erhalten, der strukturell charakterisiert wurde.

Wie bei einem Schaufelrad sind die Arylreste um eines der beiden Caesiumionen in CsP(H)Dmp (Dmp = 2,6-Dimesitylphenyl) angeordnet (siehe Bild), das jetzt synthetisiert wurde und in dem Cs+{Cs2[P(H)Dmp]3}−-Kontaktionenpaare vorliegen. Die analoge Rubidiumverbindung weist dagegen einen Rb4P4-Kubus als zentrales Strukturmotiv auf.

A binding pocket for water is created in 1 by the imidazolyl phosphane ligands and the RuII center. Compound 1 proves to be an excellent catalyst for a highly selective anti-Markovnikov hydration of terminal alkynes to give aldehydes rather than isomeric ketones under near-neutral conditions (aldehyde-to-ketone ratio up to 1000:1).

Obtention d'un bicycle MS 7 a partir des complexes de Ru et Os (Me 3 P) 3 MH PMe 2 CH 2 . Structure moleculaire