Chiral phosphites as ligands in asymmetric metal complex catalysis and synthesis of coordination compounds

Abstract

AlGaN/GaN/Si metal-insulator-semiconductor heterostructure field-effect transistors (MISHFETs) with SiN and Al 2 O 3 gate insulators are characterized by static and high-frequency measurements, and their performance is compared with nonpassivated and SiN-passivated heterostructure field-effect transistors (HFETs). The saturation drain current increased from ∼500 mA mm −1 for the HFETs to ∼770 mA mm −1 for the MISHFETs. The peak extrinsic transconductance of the MISHFETs (147 mS mm −1 for 8 nm SiN and 220 mS mm −1 for 4 nm Al 2 O 3 ) is higher than expected due to the increased gate-to-channel separation. Similarly, small signal microwave characterization yielded an increase in the current gain cut-off frequency (from 3.2 to 7.2 GHz) and the maximum frequency of oscillation (from 12.3 to 20.4 GHz) for the MISHFETs with 2 μm gate length compared to the HFET counterparts. Finally, the density of trap states, evaluated from the frequency-dependent conductance measurements, was ∼ =3 × 10 12 cm −2 eV −1 for the HFETs but only ∼ =1.8 × 10 12 cm −2 eV −1 for the MISHFETs. All of these demonstrate the capability of AlGaN/GaN MISHFETs of preparing high-performance and cost-effective devices for high-power microwave applications on a Si substrate.

MOP‐Type Binaphthyl Phosphite and Diamidophosphite Ligands and Their Application in Catalytic Asymmetric Transformations

“…[1,2,8] In general, the main advantages of phosphites include high p-acidity of the phosphorus atom, high resistance to oxidative destruction, synthetic availability and their low cost. For example, BINOL-based monophosphites, which are very efficient in asymmetric hydrogenation, are only 2 % of the price of the wellknown diphosphine BINAP.…”

“…In contrast, phosphites provide broad opportunities for fine tuning of their donor-acceptor and steric properties by incorporation of oxygen and nitrogen into the first coordination sphere of phosphorus and wide variation of the Oand N-containing building blocks. [1] This approach is now considered most practical in developing one universal ligand for different types of asymmetric catalytic reactions. As an original framework for the new ligands, we chose phosphite and diamidophosphite derivatives of rigid, axially chiral, monomethylated BINOL.…”

“…Such compounds showed excellent results in enantioselective rhodium-catalysed hydrogenation and addition of arylboronic acids, copper-catalysed addition of organozinc and organoaluminium reagents, iridiumcatalysed allylic substitution, palladium-catalysed hydrosilylation-oxidation and diboration-allylation, nickel-catalysed hydrovinylation and cycloisomerisation, ruthenium-catalysed hydrogenation of ketones and cyclopropanation. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Nevertheless, the number of chiral P monodentate phosphites that have been studied in Pd-catalysed asymmetric allylic transformations is rather limited. Meanwhile, catalytic asymmetric allylic substitution serves as one of the most powerful methods for the regio-and stereoselective formation of C À C, C À N, C À O and C À S bonds.…”

Imino‐ and Oxazolino‐Functionalised Pyrrolylphosphanes and Pyrrolylphosphinites: An Unexploited Class of Chiral P,N‐Bidentate Ligands with Unusual Electronic Properties

“…[15][16][17] It should be noted that the -P(NC 4 H 4 ) 2 building block and the common chiral ligand -PPh 2 fragment are practically the same size, according to their Tolman's cone angle values. [1,4] One could expect that such unusual electronic and steric properties of ligands with -P(NC 4 H 4 ) 2 fragments make these compounds promising for asymmetric catalysis, but to the best of our knowledge no examples of their catalytic application are known.…”

Application of Hydroxyporphyrins-based Phosphite-type Ligands to Asymmetric Pd-Catalyzed Allylic Substitution Reactions

“…Also, they can be easily prepared from readily available starting materials via simple condensation processes, including those involving parallel and solidphase synthetic procedures. [5,7,11,12,[18][19][20][21][22][23][24][25][26][27][28][29][30][31] In the case of P*-chiral phosphite-type ligands the presence of a stereogenic donor of phosphorus atom significantly promotes successful asymmetric induction in the key step of the catalytic cycle. [2,17,18,32,33] Catalytic systems based on chiral supramolecular ligands with phosphite moiety have recently attracted increasing attention.…”