Synthesis and Coordination Chemistry of Main Group Pyridyl Ligands

The bis(2-pyridyl) ligands [Me2Al(6-Me-2-py)2Li·2THF] (40) and [Me2Al(5-Me-2-py)2Li·2THF] (44) were synthesized by reacting 2-bromo-6-methylpyridine and 2-bromo-5-methylpyridine, respectively, with nBuLi at ─78 °C (1:1 equiv), followed by reaction with Me2AlCl (2:1 equiv). Reaction with 2-bromo-3-methylpyridine was attempted (45), but the crystalline material [BrLi(6-Me-py)3] was obtained. Further experiments were tried, with different R-bridgehead groups (R = Et (41), Ph (42), tBu (43)) trying to be introduced. Although some of the reactions were believed to be successful, the isolation of the products was extremely difficult, given the oily nature of most of the obtained compounds, presumably by the presence of hydrolysed material. Substitution of the Li+ cation in 40 by Na+ (46) and K+ (47) by the reaction of 40 with NaOtBu or KOtBu (1:1 equiv), respectively, was also attempted, although neither of the reactions showed successful results. Transmetallation reactions between 40 and various metals (Fe, Ca, Mn, Nb, Eu, Yb or Sm) did not yield any crystal structures. However, the reaction between the in situ ligand 41 and FeCl2 appeared to be successful. Unfortunately, no characterization analysis could be performed on it.The synthesis of the already reported [Bi(4-py)3] ligand (48) by reaction of 4-bromopyridine with nBuLi (1:1 equiv), followed by reaction with BiCl3 (3:1 equiv) is described. Further reactions with Ni(BF4)2, NiBr2, Co(BF4)2 and CoBr2 are also mentioned, although the layering of the 48 solution and the different metal solutions did not yield any crystalline material that could be observed.The NMR-scale reaction of 48 with [Bi(6-Me-2-py)3] (1:2 equiv) in d6-benzene and d8-THF was also attempted, although no change in the 1H NMR spectra could be observed, indicating that both reactions were unsuccessful. <br /

Steric Effects on the Structures, Reactivity, and Coordination Chemistry of Tris(2-pyridyl)aluminates.

Introducing substituents in the 6-position of the 2-pyridyl rings of tris(pyridyl)aluminate anions, of the type [EtAl(2-py')3 ](-) (py'=a substituted 2-pyridyl group), has a large impact on their metal coordination characteristics. This is seen most remarkably in the desolvation of the THF solvate [EtAl(6-Me-2-py)3 Li⋅THF] to give the monomer [EtAl(6-Me-2-py)3 Li] (1), containing a pyramidal, three-coordinate Li(+) cation. Similar monomeric complexes are observed for [EtAl(6-CF3 -2-py)3 Li] (2) and [EtAl(6-Br-2-py)3 Li] (3), which contain CF3 and Br substituents (R). This steric influence can be exploited in the synthesis of a new class of terminal Al-OH complexes, as is seen in the controlled hydrolysis of 2 and 3 to give [EtAl(OH)(6-R-2-py)2 ](-) anions, as in the dimer [EtAl(OH)(6-Br-2-py)2 Li]2 (5). Attempts to deprotonate the Al-OH group of 5 using Et2 Zn led only to the formation of the zincate complex [LiZn(6-Br-py)3 ]2 (6), while reactions of the 6-Br substituted 3 and the unsubstituted complex [EtAl(2-py)3 Li] with MeOH give [EtAl(OMe)(6-Br-2-py)2 Li]2 (7) and [EtAl(OMe)(2-py)2 Li]2 (8), respectively, having similar dimeric arrangements to 5. The combined studies presented provide key synthetic methods for the functionalization and elaboration of tris(pyridyl)aluminate ligands.We thank the EU for a Marie Curie Intra European Fellowship within the seventh European Community Framework Programme for R.G.-R. and an Advanced Investigator Award for D.S.W.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/chem.20150215

Wistar Kyoto Rats display anhedonia in consumption but retain some sensitivity to the anticipation of palatable solutions

The Wistar Kyoto (WKY) rat has been proposed as a model of depression-like symptoms. However, anhedonia—a reduction in the response to normatively rewarding events—as a central depression symptom has yet to be fully assessed in this model. We compared WKY rats and Wistar controls, with stress-susceptibility examined by applying mild unpredictable stress to a subset of each group. Anhedonia-like behavior was assessed using microstructural analysis of licking behavior, where mean lick cluster size reflects hedonic responses. This was combined with tests of anticipatory contrast, where the consumption of a moderately palatable solution (4% sucrose) is suppressed in anticipation of a more palatable solution (32% sucrose). WKY rats displayed greatly attenuated hedonic reactions to sucrose overall, although their reactions retained some sensitivity to differences in sucrose concentration. They displayed normal reductions in consumption in anticipatory contrast, although the effect of contrast on hedonic reactions was greatly blunted. Mild stress produced overall reductions in sucrose consumption, but this was not exacerbated in WKY rats. Moreover, mild stress did not affect hedonic reactions or the effects of contrast. These results confirm that the WKY substrain expresses a direct behavioral analog of anhedonia, which may have utility for increasing mechanistic understanding of depression symptoms

Performance of a second order electrostatic particle-in-cell algorithm on modern many-core architectures

In this paper we present the outline of a novel electrostatic, second order Particle-in-Cell (PIC) algorithm, that makes use of 'ghost particles' located around true particle positions in order to represent a charge distribution. We implement our algorithm within EMPIRE-PIC, a PIC code developed at Sandia National Laboratories. We test the performance of our algorithm on a variety of many-core architectures including NVIDIA GPUs, conventional CPUs, and Intel's Knights Landing. Our preliminary results show the viability of second order methods for PIC applications on these architectures when compared to previous generations of many-core hardware. Specifically, we see an order of magnitude improvement in performance for second order methods between the Tesla K20 and Tesla P100 GPU devices, despite only a 4× improvement in the theoretical peak performance between the devices. Although these initial results show a large increase in runtime over first order methods, we hope to be able to show improved scaling behaviour and increased simulation accuracy in the future

Stoichiometric and catalytic Si-N bond formation using the p-block base Al(NMe2)3.

The aluminium amide Al(NMe2)3 acts as a stoichiometric or catalytic reagent in dehydrogenic Si-N bond formation using amines and silanes. Although of limited substrate scope, this represents the first p-block metal catalytic system for N-H/Si-H dehydrocoupling. The observed catalytic rate law for the formation of aminosilane products in a model study of one of the catalytic reactions suggests a mechanism involving the silane component in the deprotonation of the amine (possibly in the form of a hypervalent silicon hydride).We thank The EU (ERC Advanced Investigator Grant for D.S.W., studentship for L.K.A.) and The EU (Marie Curie Intra European Fellowship for R.G.-R).This is the author accepted manuscript. The final published version is available from the Royal Society of Chemistry at http://pubs.rsc.org/en/Content/ArticleLanding/2015/DT/c5dt00662g#!divAbstract

The Coordination Chemistry of the N-Donor-Substituted Phosphazanes.

Phosph(III)azanes, featuring the heterocyclobutane P2 N2 ring, have now been established as building blocks in main-group coordination and supramolecular compounds. Previous studies have largely involved their use as neutral P-donor ligands or as anionic N-donor ligands, derived from deprotonation of amido-phosphazanes [RNHP(μ-NR)]2 . The use of neutral amido-phosphazanes themselves as chelating, H-bond donors in anion receptors has also been an area of recent interest because of the ease by which the proton acidity and anion binding constants can be modulated, by the incorporation of electron-withdrawing exo- and endo-cyclic groups (R) and by the coordination of transition metals to the ring P atoms. We observed recently that the effect of P,N-chelation of metal atoms to the P atoms of cis-[(2-py)NHP(μ-Nt Bu)]2 (2-py=2-pyridyl) not only pre-organises the N-H functionality for optimum H-bonding to anions but also results in a large increase in anion binding constants, well above those for traditional organic receptors like squaramides and ureas. Here, we report a broader investigation of ligand chemistry of [(2-py)NHP(μ-t NBu)]2 (and of the new quinolyl derivative [(8-Qu)NHP(μ-Nt Bu)]2 (8-Qu=8-quinolyl). The additional N-donor functionality of the heterocyclic substituents and its position has a marked effect on the anion and metal coordination chemistry of both species, leading to novel structural behaviour and reactivity compared to unfunctionalized counterparts.Cambridge Trus

Effects of intergroup contact and relative gratification vs. deprivation on prejudice on both sides of the U.S./Mexico status divide

A study in the U.S.–Mexican intergroup context examined how collective relative gratification (RG) versus deprivation affects the relationship between intergroup contact and interpersonal closeness and subtle prejudice towards an out‐group. Participants were Mexican university students in Mexico (N = 239) and non‐Mexican students in California (N = 90). As predicted, Mexicans experienced less gratification/higher relative deprivation (RD), and low quality intergroup contact and expressed lower interpersonal closeness and higher subtle prejudice than U.S. Americans. Differences between countries were larger amongst participants reporting higher RD. Second‐stage moderated mediation analysis showed that the mediating effects of contact between country and interpersonal closeness and subtle prejudice, respectively, were larger amongst participants who felt relatively gratified than those who felt relatively deprived. These findings underline the importance of recognizing the moderating effect of differences in the RG versus RD levels of minority and majority groups when anticipating the potential benefits of intergroup contact for prejudice reduction

Multiple deprotonation of primary aromatic diamines by LiAlH4.

Reaction of LiAlH4 with 1,2-phenylenediamine (1H4) in THF results in formation of the metallocyclic amido-/imido complex [{Al(1H2)}2{Al(1H)2}2][Li(THF)2]4 (3), while in the presence of various Lewis base ligands 1,8-diaminonaphthalene (2H4) gives the amido-('ate') complexes [Al(2H2)2](-)[Li(LL')](+) [L = THF, L' = PMDETA (N,N,N',N',N''-pentamethyldiethylenetriamine) (4); L = L' = TMEDA (N,N,N',N'-tetramethylethylenediamine) (5)]. The latter complexes provide evidence of intermediates in the proposed reaction pathway for formation of the cyclic framework of the tetraanion [{Al(1H2)}2{Al(1H)2}2](4-) of 3.We thank the EU (ERC Advanced Investigator Grant for D.S.W.), the EU (R.J.L. and L.K.A.). We also thank Dr. J. E. Davies for collecting X-ray data on 3, 4 and 5.This is the author accepted manuscript. The final version is available via RSC at http://pubs.rsc.org/en/Content/ArticleLanding/2015/DT/c4dt03802a#!divAbstract