R-allyl)M(arene)] + complexes (M ) Pd, Ni; R ) H, CH 3 , Cl; arene ) mesitylene, hexamethylbenzene) have been synthesized via halide abstraction from the corresponding allyl halide dimers, [(allyl)MX] 2 , using either AgSbF 6 in the case of M ) Pd or NaB(Ar f ) 4 (Ar f ) 3,5-(CF 3 ) 2 C 6 H 3 ) in the case of M ) Ni. The [(allyl)Ni(mesitylene)] + and [(2-methallyl)Ni(hexamethylbenzene)] + salts have been characterized by single-crystal X-ray diffraction. The arene ligands in the Pd species are highly labile. The mesitylene ligand in the [(2-R-allyl)Pd(mesitylene)] + complexes is rapidly displaced at temperatures as low as -120 °C by olefins and alkynes (ethylene, tert-butylethylene, cyclopentene, cyclohexene, cyclooctene, 2-butyne) to yield the bis-olefin or bis-alkyne complexes, which have been characterized by NMR spectroscopy. [(allyl)Pd(mesitylene)] + undergoes rapid degenerate exchange with free mesitylene at low temperatures (∆G q ) 10.2 kcal/mol). The arene ligand of the Ni complexes is less labile. Displacement of mesitylene from [(allyl)Ni(mesitylene)] + by excess diethyl ether at 25 °C yields [(allyl)Ni(Et 2 O) 2 ] + . Reaction of the [(2-R-allyl)Ni(mesitylene)] + complexes (R ) H, CH 3 ) with R-olefins at 25 °C yields new allyl complexes plus propene (when R ) H) or isobutylene (when R ) CH 3 ). A mechanism involving intramolecular hydrogen migration is proposed to account for these transformations.

Several cationic (allyl)Pd(II) complexes were synthesized and shown to be highly active for (2,3)-vinyl addition polymerization of norbornene (NB) to yield polymers with low molecular weight distributions (MWDs) ranging from 1.2-1.4. Despite the low MWDs, slow initiation was followed by rapid propagation preventing molecular weight control of the poly(norbornene). Several intermediates in these polymerizations initiated with [(2-R-allyl)Pd(mesitylene)](+) complexes were fully characterized (NMR and X-ray diffraction). Consistent with previous observations the allyl and NB units couple in cis-exo fashion to yield a sigma,pi-complex capped by mesitylene. Mesitylene is readily displaced by NB to form an agostic intermediate in which NB acts as a bidentate ligand and binds to the cationic Pd center via the pi-system and a gamma-agostic interaction with the syn hydrogen at C7. The identity of this complex was established by NMR spectroscopy and single-crystal X-ray diffraction. It is significant since it suggests bidentate binding of NB in the propagating species, which cannot be observed by NMR spectroscopy. The NMR studies suggest that the second insertion, i.e., insertion of NB in the agostic intermediate, is the slow initiation step and the subsequent insertions are extremely fast. Therefore, slow chelate opening is the major limitation preventing a living polymerization. This hypothesis was explored using a series of cationic substituted pi-allyl complexes; significantly increased reactivity was observed when electron-withdrawing groups were introduced into the allyl moiety. However, despite these modifications initiation remained slow relative to chain propagation.

Alkali metals absorbed into silica gel yield three stages of unique loose black powders (M-SG) that are strong reducing agents. All react nearly quantitatively with water to form hydrogen. Liquid Na-K alloys form air-sensitive powders at room temperature that can be converted at 150 degrees C to a form that is sensitive to moisture but not to dry air. Slowly heating sodium and silica gel to 400 degrees C yields a third type that can be handled in ambient air with only slow degradation by atmospheric moisture. These materials eliminate many hazards associated with pure alkali metals and provide easily handled reducing agents and hydrogen sources. They could be used in continuous-flow reactors to reduce and protonate aromatics, dechlorinate alkyl and aryl halides, and desulfurize various compounds.

Reliable and rapid analysis remains a high priority for quality control in biodiesel production. Quantifying biodiesel with alternative analytical tools such as proton nuclear magnetic resonance ( 1 H NMR) can provide total methyl esters distributions without significant sample pretreatment. Using unique spectra of individual methyl esters, we investigate the feasibility of using 1 H NMR spectroscopy to identify and quantify relative and absolute concentrations of methyl esters in a biodiesel.

Liquid Na-K alloys are readily absorbed by silica gel (SG) to form shiny black stage 0 powders, which form stage I powders upon heating to about 150°C. Uniform black powders of stage I Na-SG are prepared by heating Na with SG to about 165°C. Na metal and SG react to form uniform powders of stage II Na-SG by slow heating to 400°C. Stage II powders of Na-SG are easily handled in an open ambient environment and do not change with time when kept in a closed container. The powerful reducing properties of alkali metal-silica gel adducts should permit the use of continuous-flow columns for the reduction of organic and inorganic compounds. In addition, they have the ability to provide hydrogen gas on demand from air-stable, easily handled sources that can be stored indefinitely. -(DYE*, J. L.; CRAM, K. D.; URBIN, S. A.; REDKO, M. Y.; JACKSON, J. E.; LEFENFELD, M.; J. Am. Chem. Soc. 127 (2005) 26, 9338-9339; Dep. Chem., Mich. State Univ., East Lansing, MI 48824, USA; Eng.) -W. Pewestorf 41-212

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2003 Zeolites Zeolites V 1350 Inorganic Electrides Formed by Alkali Metal Addition to Pure Silica Zeolites. -Up to four Cs or Rb atoms per 32 Si atoms can be incorporated into the channels of the zeolites ITQ-4 and beta with effective oxidation states of zero. The metals ionize to form cations and delocalized electrons, as confirmed by diffusive reflectance, 133 Cs, and 29Si MAS NMR spectroscopy. K and Na can also be absorbed at higher temperature, but their final spectra show no evidence of delocalized electrons. -(WERNETTE, D. P.; ICHIMURA, A. S.; URBIN, S. A.; DYE*, J. L.; Chem. Mater. 15 (2003) 7, 1441-1448; Dep. Chem., Mich. State Univ., East Lansing, MI 48824, USA; Eng.) -W. Pewestorf 26-242