A high-spin square-planar Fe(ii) complex stabilized by a trianionic pincer-type ligand and conclusive evidence for retention of geometry and spin state in solution

Square-planar high-spin Fe(ii) molecular compounds are rare and the only three non-macrocyclic or sterically-driven examples reported share a common FeO₄ core. Using an easily modifiable pincer-type ligand, the successful synthesis of the first compound of this type that breaks the FeO₄ motif was achieved. In addition, we present the first evidence that geometry and spin state persist in solution. Extensive characterization includes the first high-field EPR and variable field/temperature Mössbauer spectra for this class of compounds. Analysis of the spectroscopic data indicates this complex exhibits a large and positive zero-field splitting tensor. Furthermore, the unusually small ΔE _Q value determined for this compound is rationalized on the basis of DFT calculations.     

An OCO3- trianionic pincer tungsten(VI) alkylidyne: rational design of a highly active alkyne polymerization catalyst

Synthesis, characterization, and catalytic alkyne polymerization results for the first trianionic pincer alkylidyne complex, [(t)BuOCO]W≡CC(CH(3))(3)(THF)(2) (6), are described. Complex 6 is a highly active catalyst for the polymerization of acetylenes and exhibits a high turnover number (4371), activity (1.05 × 10(6) g(PPA) mol(cat)(-1) h(-1)),and yield (87%) for the polymerization of 1-ethynyl-4-fluorobenzene.     

A new method for generating organosilanones

A new method for the generation of organosilanones by the reaction of betaines, R₃P⁺-CR¹R²-SiR³R⁴-S^–, with (Et₃Sn)₂O was suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2246–2247, December, 1994.This study was financially supported by the Russian Foundation for Basic Research, Project No. 94-03-09710.     

A highly effective bifunctional ligand for radioimmunotherapy applications

A novel bifunctional ligand (3p-C-NETA) for antibody-targeted radioimmunotherapy (RIT) of β-emitting radioisotopes (90)Y and (177)Lu was efficiently synthesized via an unexpected regiospecific ring opening of an aziridinium ion. 3p-C-NETA instantly formed a very stable complex with (90)Y or (177)Lu. 3p-C-NETA is an excellent bifunctional ligand for RIT.     

A hybrid phosphorus ligand for highly enantioselective asymmetric hydroformylation

A new hybrid phosphorus ligand has been prepared starting from chiral NOBIN (2-amino-2'-hydroxy-1,1'-binaphthyl). Excellent enantioselectivities (up to 99% ee) have been achieved in the Rh-catalyzed asymmetric hydroformylations of styrene derivatives and vinyl acetate.     

A new method for the conversion of allyl alcohol into pi-allyl species promoted by nucleophilic interaction with a CO ligand

Upon treatment with an iridium carbonyl complex, [(PN)Ir(CO)2]+, allyl alcohol can be smoothly converted into pi-allyliridium species at ambient temperature via nucleophilic interaction of the alcohol with a CO ligand followed by C(allyl)-O bond cleavage in the resultant protonated allyloxycarbonyl intermediate.     

Dichloromethane as an unusual methylene equivalent. A new entry of highly nucleophilic and selective titanium-methylene complexes for ester methylenation

[reaction: see text] The successful application of CH2Cl2-Mg-TiCl4-system mediated methylenation of various esters such as tert-butyl ester and 2,5-cyclohexadiene-1-carboxylate highlights the extraordinary reactivity, selectivity, and the nonbasic nature of this new methylene-carbenoid, which serves as a practical reagent applicable to large-scale synthesis.     

A tetraphosphorus ligand for highly regioselective isomerization-hydroformylation of internal olefins

A new pyrrole-based tetraphosphorus ligand capable of forming multiple chelating modes has been prepared. Higher regioselectivity has been achieved in the rhodium-catalyzed isomerization-hydroformylations of internal olefins compared with its bisphosphorus analogue.     

A highly selective catalytic method for the oxidative functionalization of C-H bonds

This communication describes a new and highly practical Pd(II)-catalyzed method for the regio- and chemoselective oxidative functionalization of arenes and alkanes. Carbon-hydrogen bonds of substrates that contain a variety of directing groups (e.g., pyridine, azobenzene, pyrazole, and imine derivatives) are selectively transformed into esters, ethers, and aryl-halides under mild conditions. The scope of this reaction in terms of substrate, directing group, and oxidant is described, and a preliminary catalytic cycle is proposed.     

Catalytic asymmetric cleavage of sp3 C-N bonds for access to highly enantioenriched N-benzylic sulfonamides

In the presence of 10 mol% of a chiral phosphoric acid, a variety of racemic N-benzylic sulfonamides having N-(3-indolyl)methyl groups smoothly undergo kinetic resolution with benzyl thiol at 0 °C or at room temperature and the remaining sulfonamides are recovered in moderate to excellent yields and with excellent ee.     

A new nucleophilic addition/ring-closure sequence. Enantioselective synthesis of 3-deoxy-8-oxatropanes

[reaction: see text] A study of new nucleophilic addition/ring-closure (NARC) sequences has resulted in the development of a stereoselective synthetic route to 3-deoxy-8-oxatropanes. The new sequences consisted of either a syn or anti aldol addition, employing an omega-alkenoyl sultam, followed by two-step bicyclic ring construction involving, consecutively, ring-closing metathesis and intramolecular oxymercuration.     

Me-AnilaPhos: a new chiral phosphine-phosphoramidite ligand for a highly efficient Rh-catalyzed asymmetric olefin hydrogenation

A cationic rhodium(I) complex with a novel chiral phosphine-phosphoramidite ligand based on 2-diphenylphosphino-N-methylaniline and R-BINOL moieties has been synthesized. The complex provided remarkably high activity and enantioselectivity in the asymmetric hydrogenation of methyl (Z)-α-acetamidocinnamate (100% conversion after 10 min, 98% ee) and dimethyl itaconate (100% conversion after 26 min, 96% ee) under ambient conditions (1 bar hydrogen pressure, room temperature) using 1 mol % of the catalyst in dichloromethane as solvent. On the other hand, when hydrogenation was performed in methanol, both conversion and enantioselectivity were significantly diminished, due to the partial decomposition of the rhodium/phosphine-phosphoramidite complex.     

CuCl-K(2)CO(3)-catalyzed highly selective borylcupration of internal alkynes - ligand effect

An efficient and practical copper-catalyzed highly regio- and stereoselective borylcupration of internal alkynes with bis(pinacolato)diboron using a catalytic amount of K(2)CO(3) as base producing Z-alkenylboron compounds has been demonstrated by applying the ligand effect: commercially available electron-rich tris(p-methoxyphenyl) phosphine ensures a smooth and efficient reaction. Functionalized alkynes, such as propargylic alcohols and derivatives as well as N-propargyl tosylamide, may also be used with excellent selectivity.     

A new pyrrolidine-derived atropisomeric amino alcohol as a highly efficient chiral ligand for the asymmetric addition of diethylzinc to aldehydes

A highly efficient pyrrolidine-derived atropisomeric amino alcohol, (S_a)-1-[2-diphenylhydroxymethyl-6-(trifluoromethyl)phenyl]-2-(1-pyrrolido)methyl-1H-pyrrole, has been synthesized as a chiral ligand for the enantioselective addition of diethylzinc to some prochiral aldehydes to afford (S)-alcohols. The conversion rates were close to quantitative with good to excellent enantiomeric excesses (up to 95% ee).     

A new mechanism for nucleophilic substitution at a thiophosphoryl centre revealed by the reaction of diisopropylamine with PSCl3

The reaction of PSCl3 with Pr(i)2NH at 60 degrees C affords the disubstitution product (Pr(i)2N)2P(S)Cl without first forming the monosubstitution product Pr(i)2NP(S)Cl2; a P(III) compound (possibly PCl3) generated in situ seems to be a crucial intermediate.     

A new tetradentate ligand for atom transfer radical polymerization

The properties of a ligand, including molecular structure and substituents, strongly affect the catalyst activity and control of the polymerization in atom transfer radical polymerization (ATRP). A new tetradentate ligand, N,N′‐bis(pyridin‐2‐ylmethyl‐3‐hexoxo‐3‐oxopropyl)ethane‐1,2‐diamine (BPED) was synthesized and examined as the ligand of copper halide for ATRP of styrene (St), methyl acrylate (MA), and methyl methacrylate (MMA), and compared with other analogous linear tetrdendate ligands. The BPED ligand was found to significantly promote the activation reaction: the CuBr/BPED complex reacted with the initiators so fast that a large amount of Cu(II)Br₂/BPED was produced and thus the polymerizations were slow for all the monomers. The reaction of CuCl/BPED with the initiator was also fast, but by reducing the catalyst concentration or adding CuCl₂, the activation reaction could be slowed to establish the equilibrium of ATRP for a well‐controlled living polymerization of MA. CuCl/BPED was found very active for the polymerization of MA. For example, 10 mol% of the catalyst relatively to the initiator was sufficient to mediate a living polymerization of MA. The CuCl/BPED, however, could not catalyze a living polymerization of MMA because the resulting CuCl₂/BPED could not deactivate the growing radicals. The effects of the ligand structures on the catalysis of ATRP are also discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3553–3562, 2004     

BINAS - synthesis and use of a new ligand for propylene hydroformylation

BINAS is a new, very efficient ligand for propylene hydroformylation. BINAS is made by the sulfonation of NAPHOS. Different synthetic routes to NAPHOS are discussed. A new two step synthesis starting from 2,2′-bis(bromomethyl)-1,1′-binaphthyl is described.