Chelating diphos ligands with inorganic backbones. Crystal structure of [PtCl2{(PPh2O)2SiPh2}]

The metallo-phosphaalkenes (η⁵-C₅Me₅)(CO)₂FeP=C(R)(SiMe₃) (Ia: R = SiMe₃, Ib: R = Ph) and MeO₂C---CC---CO₂Me undergo a dipolar [3+2]-cycloaddition to afford the metallo-heterocycles [(η⁵-C₅Me₅)(CO)

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=C(R)SiMe₃] (IIIa,b) with exocyclic P=C double bonds.     

2,2′-Bis((di-tert-butylphosphino)methyl)-1,1′-biphenyl (ditbi): a bulky analogue of bisbi. The crystal structure of [Rh2Cl2(1,5-cod)2(μ-ditbi)]

Diphosphine 2,2′-bis(di-tert-butylphosphino)methyl)-1,1′-biphenyl (ditbi) is synthesised by the addition of to 2,2′-bis(bromomethyl)-1,1′-biphenyl, followed by deprotection with diethylamine. Treatment of [Rh₂Cl₂(1,5-cod)₂], with ditbi gives [Rh₂Cl₂(1,5-cod)₂(μ-ditbi)] (2) as confirmed by its X-ray crystal structure determination. Hydroformylation of 1-hexene using [Rh(acac)(CO)₂]/ditbi as catalyst gave n- and iso-heptanal in a ratio of 1:1.     

The temperature dependence of the Mössbauer hyperfine parameters in Nd2Fe14B

We have determined the temperature dependence of the internal hyperfine field, isomer shift, and quadrupole shift at each of the six iron sites in Nd₂Fe₁₄B. The hyperfine parameters are consistent with the local iron site environments. The quadrupole and isomer shifts and their temperature dependences support our assignments of the relative ordering of the internal hyperfine fields as j₂>k₂>ck₁>j₁>c. We obtain a Mössbauer temperature of 390 K for Nd₂Fe₁₄B, which compares well with the Debye temperature of 420K for pure iron.     

Pyrrolidines and Piperidines by Ligand‐Enabled Aza‐Heck Cyclizations and Cascades of N‐(Pentafluorobenzoyloxy)carbamates

Ligand‐enabled aza‐Heck cyclizations and cascades of N‐(pentafluorobenzoyloxy)carbamates are described. These studies encompass the first examples of efficient non‐biased 6‐exo aza‐Heck cyclizations. The methodology provides direct and flexible access to carbamate protected pyrrolidines and piperidines.     

Structure and transport properties of a plastic crystal ion conductor: diethyl(methyl)(isobutyl)phosphonium hexafluorophosphate

Understanding the ion transport behavior of organic ionic plastic crystals (OIPCs) is crucial for their potential application as solid electrolytes in various electrochemical devices such as lithium batteries. In the present work, the ion transport mechanism is elucidated by analyzing experimental data (single-crystal XRD, multinuclear solid-state NMR, DSC, ionic conductivity, and SEM) as well as the theoretical simulations (second moment-based solid static NMR line width simulations) for the OIPC diethyl(methyl)(isobutyl)phosphonium hexafluorophosphate ([P(1,2,2,4)][PF(6)]). This material displays rich phase behavior and advantageous ionic conductivities, with three solid-solid phase transitions and a highly "plastic" and conductive final solid phase in which the conductivity reaches 10(-3) S cm(-1). The crystal structure shows unique channel-like packing of the cations, which may allow the anions to diffuse more easily than the cations at lower temperatures. The strongly phase-dependent static NMR line widths of the (1)H, (19)F, and (31)P nuclei in this material have been well simulated by different levels of molecular motions in different phases. Thus, drawing together of the analytical and computational techniques has allowed the construction of a transport mechanism for [P(1,2,2,4)][PF(6)]. It is also anticipated that utilization of these techniques will allow a more detailed understanding of the transport mechanisms of other plastic crystal electrolyte materials.     

Factors Influencing Elementary Teachers' Positioning of African American Girls as Science and Mathematics Learners

Despite recent progress toward gender equity in science and mathematics education, the underachievement of low‐income African American girls remains a challenge when compared with their white counterparts. Furthermore, the causes of this persistent underachievement have not been explored thoroughly. We have initiated a three‐year longitudinal study of how African American girls position themselves in relation to science and mathematics learning from fifth to seventh grade, including the impact, if any, of the positioning of teachers, counselors, and parents on this process. In this article, we share findings examining science and mathematics teachers' actions and perceptions and their positioning of African American girls. This qualitative study used an interpretive design with multiple data sources including classroom observations, interviews, and field notes. Findings reveal that school‐wide policies and teachers' autonomous decisions impact the regularity of science and mathematics instruction, and that teachers do not always conceptualize the girls as science and mathematics achievers, positioning them in negative ways.     

Bis-trifluoromethyl Effect: Doubled Transitions in the Rotational Spectra of Hexafluoroisobutene, (CF(3))(2)C═CH(2)

Rotational spectra for hexafluoroisobutene, and its (13)C isotopologues, have been recorded between 8 and 16 GHz using a chirped pulse, Fourier transform microwave spectrometer. Notably, all spectra observed are doubled with separations between the doublets being between 1 and 60 MHz. We propose that the bis-trifluoromethyl groups of the target molecule are staggered in the equilibrium configuration, and that a novel, out-of-phase rotation through a F-CCC-F planar configuration with low barrier (<100 cm(-1)), leads to the observed doubled rotational spectra.     

Lewis base ionic liquids

Ionic liquids which are (weak) Lewis bases have a number of interesting and useful properties different to those of traditional ionic liquids, including volatility and the possibility of being distillable in some cases, a base catalysis effect in others and enhancement of the acidity of dissolved acids.     

Chiral palladium bis(phosphite)PCP-pincer complexes via ligand C-H activation

The synthesis of a range of chiral palladium bis(phosphite) pincer complexes has been achieved via C-H activation of the parent ligands and one of the complexes formed shows good activity in the catalytic allylation of aldehydes.     

Using nonlinear transient growth to construct the minimal seed for shear flow turbulence

Linear transient growth analysis is commonly used to suggest the structure of disturbances which are particularly efficient in triggering transition to turbulence in shear flows. We demonstrate that the addition of nonlinearity to the analysis can substantially change the prediction made in pipe flow from simple two-dimensional streamwise rolls to a spanwise and cross-stream localized three-dimensional state. This new nonlinear optimal is demonstrably more efficient in triggering turbulence than the linear optimal indicating that there are better ways to design perturbations to achieve transition.