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Zirconium complexes {L}ZrClx(THF)n [L = 2-(C4H3N-2′-CH=N)C2H4NHPh, x = 3, n = 1, 2a; L = 2-(C4H3N-2′-CH=N)C6H4-2-OPh, x = 3, n = 0, 2b; L = 2-(C4H3N-2′-CH=N)C6H4-2-SPh, x = 3, n = 1, 2c; L = 2-(C4H3N-2′-CH=N)CH2C6H4-2-OMe, x = 3, n = 0, 2d; L = 2-(C4H3N-2′-CH=N)C2H4NPh, x = 2, n = 0, 4a] were prepared and characterized by elemental analysis, NMR spectroscopy, and by X-ray crystallography for 2a and 4a. In the solid state, 2a and 4a are monomeric with the pyrrolide-imino-amine adopting a mer-configuration. Upon activation with methylaluminoxane (MAO), all Zr(iv) precatalysts were active in ethylene polymerization and exhibited high thermal stability operating effectively at 100 °C with activities up to 453 kg(PE) mol[Zr]−1 h−1. The high-density polyethylenes produced are strictly linear with melting temperatures in the range of 134–136 °C, and crystallinities varying from 56% to 70%. [ABSTRACT FROM AUTHOR]

Application of CO2 as a renewable feedstock and C1 building block for production of commodity and fine chemicals is a highly challenging but obvious industry-relevant task. Of particular interest is the catalytic coupling of CO2 with inexpensive unsaturated hydrocarbons (olefins, dienes, styrenes, alkynes), providing direct access to carboxylic acids and their derivatives. Although not brand new for the scientific community, it is still a complete challenge, as no truly effective catalytic system has been reported to date. In this Perspective, we discuss the available experimental, theoretical and mechanistic data for such homogeneously catalyzed carboxylation processes. A special focus is placed on the understanding of the key elementary steps and of some thermodynamic and kinetic constraints. [ABSTRACT FROM AUTHOR]

Chromium(iii) complexes [CrCl2(L)(THF)] based on monoanionic tridentate ligands [2a, L = {2-(C4H3N-2′-CH=N)C2H4NHPh}; 2b, L = {5-tert-butyl-2-(C4H2N-2′-CH=N)C2H3NHPh}; 2c, L = {2-(C4H3N-2′-CH=N)C2H4OPh}] have been prepared. Complexes 2a and b were converted into the monomeric acetonitrile adducts [CrCl2(L)(NCMe)] [3a, L = {2-(C4H3N-2′-CH=N)C2H4NHPh}; 3b, L = {5-tert-butyl-2-(C4H2N-2′-CH=N)C2H3NHPh}] by reaction with acetonitrile at room temperature. All Cr complexes were characterized by IR spectroscopy, elemental analysis, magnetochemistry for 2a–c, and by X-ray crystallography for 3a and 3b. Upon activation with methylaluminoxane (MAO), chromium precatalysts 2a and 2c showed good activity in ethylene oligomerization (TOF = 47.0–57.0 × 103 (mol ethylene)(mol Cr)−1 h−1 at 80 °C), producing mostly oligomers (93.0–95.6 wt% of total products). On the other hand, under identical oligomerization conditions, 2b/MAO behaved as a polymerization catalyst generating predominantly polyethylene (73.0 wt%). However, the catalytic behavior of the precatalyst 2b can be adjusted by varying the MAO-to-Cr ratio. Thus, the use of 500 equiv. causes a dramatic shift from polymerization to ethylene oligomerization, eventually producing mainly lighter α-olefin fractions [α-C4 (68.7 wt%) and α-C6 (19.2 wt%)]. A further increase in the amount of MAO (1000 equiv.) leads to a more balanced distribution of oligomers, with a drastic decrease in the α-C4 and increase in the α-C8 fractions. [ABSTRACT FROM AUTHOR]

This article presented the design of two band reject filters in the BAW technology. The two designs show different benefits. The ladder T topology has a better rejection bandwidth than the ladder topology because the bandwidth is controlled by resonance and antiresonance frequencies, which are selected by the loading layer. Moreover, the bandwidth is adjustable by the design. This setup presents a steeper rejection slope. The insertion loss can be reduced by increasing the bottom electrode's thickness. However, the fabrication process and the control of resonance frequency are more difficult since antiresonance frequencies of series resonators depend on the thickness of the loading layers. [ABSTRACT FROM PUBLISHER]

The capacitive coupling between two microstrip lines crossing diagonally above a ground plane in a multilayered dielectric substrate is analyzed through a quasistatic approach based on the space-domain integral equation method, The typical evolutions of the normalized lumped excessive capacitances for nonorthogonal crossover configurations are presented. [ABSTRACT FROM AUTHOR]

A clever way to simulate Numerically Matched Loads is presented and applied in the mathematical framework of 3-D spectral domain analysis. The numerically matched loads already have been developed in the particular case of the spectral domain approach using a set of subsectional rooftop expansion and testing functions in the moment method. In order to properly model more complicated structures, we propose in this letter an extension of the NML simulation where triangular subdomain functions are used as both expansion and testing functions in the moment method. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 15: 373–377, 1997. [ABSTRACT FROM AUTHOR]

This article presents a full-wave analysis of coplanar waveguide, discontinuities using a spectral-domain approach. Based on a magnetic field integral formulation, the equivalent magnetic current distribution on the apertures is solved by a moment method. The scattering parameters are numerically measured with the help of numerically matched loads placed at each port of the discontinuities. [ABSTRACT FROM AUTHOR]

Dinuclear complexes of aluminum and indium with a bis(phenoxy-imine) platform have been synthesized and used in the polymerization of lactide. Kinetic studies demonstrate that the dialuminum precursor provides a more favorable reaction pathway in terms of activation free energy than that of directly related monoaluminum systems. No similar trend is observed with the corresponding diindium–monoindium systems, which is attributed to a dissimilar ROP mechanism. [ABSTRACT FROM AUTHOR]

Lamb wave devices have recently gained an interest for providing narrow bandpass filters in wireless transmission systems. Their cointegration with film bulk acoustic wave resonators is a major advantage, enabling the possibility to provide simultaneously several radio frequency and intermediate-frequency filters in a single fabrication. Similarly, in this work, we report the fabrication of resonators using waves guided in a piezoelectric layer deposited atop a Bragg mirror. Such waves exhibit a behavior close to Lamb waves, thanks to the acoustic isolation provided by the mirror, while being cointegrated along with solidly mounted resonator structures. [ABSTRACT FROM AUTHOR]

Application of CO2 as a renewable feedstock and C1 building block for production of commodity and fine chemicals is a highly challenging but obvious industry-relevant task. Of particular interest is the catalytic coupling of CO2 with inexpensive unsaturated hydrocarbons (olefins, dienes, styrenes, alkynes), providing direct access to carboxylic acids and their derivatives. Although not brand new for the scientific community, it is still a complete challenge, as no truly effective catalytic system has been reported to date. In this Perspective, we discuss the available experimental, theoretical and mechanistic data for such homogeneously catalyzed carboxylation processes. A special focus is placed on the understanding of the key elementary steps and of some thermodynamic and kinetic constraints.

Chromium(iii) complexes [CrCl2(L)(THF)] based on monoanionic tridentate ligands [, L = {2-(C4H3N-2'-CH[double bond, length as m-dash]N)C2H4NHPh}; , L = {5-tert-butyl-2-(C4H2N-2'-CH[double bond, length as m-dash]N)C2H3NHPh}; , L = {2-(C4H3N-2'-CH[double bond, length as m-dash]N)C2H4OPh}] have been prepared. Complexes and were converted into the monomeric acetonitrile adducts [CrCl2(L)(NCMe)] [, L = {2-(C4H3N-2'-CH[double bond, length as m-dash]N)C2H4NHPh}; , L = {5-tert-butyl-2-(C4H2N-2'-CH[double bond, length as m-dash]N)C2H3NHPh}] by reaction with acetonitrile at room temperature. All Cr complexes were characterized by IR spectroscopy, elemental analysis, magnetochemistry for , and by X-ray crystallography for and . Upon activation with methylaluminoxane (MAO), chromium precatalysts and showed good activity in ethylene oligomerization (TOF = 47.0-57.0 × 10(3) (mol ethylene)(mol Cr)(-1) h(-1) at 80 °C), producing mostly oligomers (93.0-95.6 wt% of total products). On the other hand, under identical oligomerization conditions, /MAO behaved as a polymerization catalyst generating predominantly polyethylene (73.0 wt%). However, the catalytic behavior of the precatalyst can be adjusted by varying the MAO-to-Cr ratio. Thus, the use of 500 equiv. causes a dramatic shift from polymerization to ethylene oligomerization, eventually producing mainly lighter α-olefin fractions [α-C4 (68.7 wt%) and α-C6 (19.2 wt%)]. A further increase in the amount of MAO (1000 equiv.) leads to a more balanced distribution of oligomers, with a drastic decrease in the α-C4 and increase in the α-C8 fractions.

To model the Ti-olefin interaction in the putative [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(R')(olefin)(+) intermediates in "constrained geometry" Ti-catalyzed olefin polymerization, chelated alkoxide olefin complexes [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))(+) have been investigated. The reaction of [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(2) (1a,b; R = H, Me) with HOCMe(2)CH(2)CH(2)CH=CH(2) yields mixtures of [eta(5)-C(5)R(4)SiMe(2)NH(t)Bu]TiMe(2)(OCMe(2)CH(2)CH(2)CH=CH(2)) (2a,b) and [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(OCMe(2)CH(2)CH(2)CH=CH(2)) (3a,b). The reaction of 2a/3a and 2b/3b mixtures with B(C(6)F(5))(3) yields the chelated olefin complexes [[eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][MeB(C(6)F(5))(3)] (4a,b; 71 and 89% NMR yield). The reaction of 2b/3b with [Ph(3)C][B(C(6)F(5))(4)] yields [[eta(5): eta(1)-C(5)Me(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][B(C(6)F(5))(4)] (5b, 88% NMR yield). NMR studies establish that 4a,b and 5b exist as mixtures of diastereomers (isomer ratios: 4a/4a', 62/38; 4b/4b', 75/25; 5b/5b', 75/25), which differ in the enantioface of the olefin that is coordinated. NMR data for these d(0) metal olefin complexes show that the olefin coordinates to Ti in an unsymmetrical fashion primarily through C(term) such that the C=C pi bond is polarized with positive charge buildup on C(int). Dynamic NMR studies show that 4b/4b' undergoes olefin face exchange by a dissociative mechanism which is accompanied by fast inversion of configuration at Ti ("O-shift") in the olefin-dissociated intermediate. The activation parameters for the conversion of 4b to 4b' (i.e., 4b/4b' face exchange) are: DeltaH = 17.2(8) kcal/mol; DeltaS = 8(1) eu. 4a/4a' also undergoes olefin face exchange but with a lower barrier (DeltaH = 12.2(9) kcal/mol; DeltaS = -2(3) eu), for the conversion of 4a to 4a'.