A Suzuki Coupling Based Route to 2,2'-Bis(2-indenyl)biphenyl Derivatives

Because of the promising performance in olefin polymerization of 2,2'-bis(2-indenyldiyl)biphenyl zirconium dichloride, we developed a new and broadly applicable route to 2,2'-bis(2-indenyl)biphenyl derivatives. Reaction of the known 2,2'-diiodobiphenyl with the new 2-indenyl boronic acid did not result in the desired 2,2'-bis(2-indenyl)biphenyl (10); instead an isomer thereof, (spiro-1,1-(2,2'-biphenyl)-2-(2-indenyl)indane), was obtained. It was found that compound 10 could be made via a palladium-catalyzed reaction of 2,2-biphenyldiboronic acid with 2-bromoindene under standard Suzuki reaction conditions. However, the yield of this reaction was low at low palladium catalyst loadings, due to a competitive hydrolysis reaction of 2,2-biphenyldiboronic acid. HTE techniques were used to find an economically viable protocol. Thus, use of the commercially available 1.0 molar solution of (n-Bu)4NOH in methanol with cosolvent toluene led to precipitation of the pure product in a fast and clean reaction, using only 0.7 mol % (0.35 mol % per C-C) of the expensive palladium catalyst.

Methyl Complexes of the Transition Metals

Organometallic chemistry can be considered as a wide area of knowledge that combines concepts of classic organic chemistry, that is, based essentially on carbon, with molecular inorganic chemistry, especially with coordination compounds. Transition-metal methyl complexes probably represent the simplest and most fundamental way to view how these two major areas of chemistry combine and merge into novel species with intriguing features in terms of reactivity, structure, and bonding. Citing more than 500 bibliographic references, this review aims to offer a concise view of recent advances in the field of transition-metal complexes containing M-CH fragments. Taking into account the impressive amount of data that are continuously provided by organometallic chemists in this area, this review is mainly focused on results of the last five years. After a panoramic overview on M-CH compounds of Groups 3 to 11, which includes the most recent landmark findings in this area, two further sections are dedicated to methyl-bridged complexes and reactivity.Ministerio de Ciencia e Innovación Projects CTQ2010–15833, CTQ2013-45011 - P and Consolider - Ingenio 2010 CSD2007 - 00006Junta de Andalucía FQM - 119, Projects P09 - FQM - 5117 and FQM - 2126EU 7th Framework Program, Marie Skłodowska - Curie actions C OFUND – Agreement nº 26722

Taalkundige aanmerkingen over verouderde en minverstaanbaare woorden in de staaten overzetting des bijbels /

Europeana-GoogleBook

Muscle length and neuromuscular transmission in the frog

The effect of muscle length on the probability of neuromuscular transfer for whole frog muscle was studied in vivo at different stimulus frequencies. First the relationship between the steady state amplitude of the compound muscle action potential and stimulus frequency was measured at standard muscle lenght, l1/2, which is the mean of maximal and minimal muscle length in situ. The result shows that the collection of nerve muscle junctions acts as a "low pass filter" for neuromuscular spike transmission with a 50% "pass through" at about 1 Hz for the standard length. At a given stimulus frequency in the range of 0.125 to 8 Hz, a stepwise increase of muscle length from l1/2, within the physiological range, was found to cause an increase of the compound muscle action potential amplitude with an initial overshoot, while a decrease of length caused a decrease of the amplitude with an initial undershoot. The relation between the amplitude of the initial response and muscle length depends on stimulus frequency, and on the degree of curarization. Its shape is sigmoidal at about 50% spike transmission. The results suggest that the maximal physiological change of muscle length can change the difference between the average endplate potential peak amplitude and the average threshold potential up to a value, which is equal to two times the standard deviation of the endplate peak potential distribution of the junctions. For the steady state response to changes in muscle length this effect is smaller. We suggest that the observed effect of muscle length on neuromuscular transmission plays an important role in the control of whole muscle contraction

Synthesis, solid state and DFT structure and olefin polymerization capability of a unique base-free dimeric methyl titanium dication

Reaction of Cp*Ti{NC(ArF2)NiPr2}Me2 (1, ArF2 = 2,6-C6H3F2) with [Ph3C][B(C6F5)4] gave the base-free structurally authenticated dication [Cp*2Ti2{NC(ArF2)NiPr2}2(μ-Me)2][B(C6F5)4]2 (3-[BF20]2) containing two doubly α-agostic bridging methyl groups. 3-[BF20]2 is a highly effective ethylene–propylene polymerization catalyst at 90 °C, and its performance is identical to the catalyst generated in situ from 1 and [Ph3C][B(C6F5)4]

Methylaluminoxane as an Alternative for BArF in the Iridium-Catalyzed Asymmetric Hydrogenation of Imines

BArF has been the anion of choice for iridium-catalyzed imine hydrogenation; however, for large-scale production its use may be too costly. Methylaluminoxane (MAO) can be used instead in conjunction with [{Ir(COD)Cl}2], although enantioselectivities are somewhat lower than with BArF if 50–500 eq. of MAO are used.