Chloro(η6‐p‐cymene)(phosphoramidite)ruthenium(II), a 16‐Electron Fragment Stabilized by an η2‐Aryl–Metal Interaction,and Its Use in Asymmetric Cyclopropanation

Chloride abstraction from the half‐sandwich complexes [RuCl₂(η⁶‐p‐cymene)(P*‐κP)] ( 2a : P* = (S_a,R,R)‐ 1a = (1S_a)‐[1,1′‐binaphthalene]‐2,2′‐diyl bis[(1R)‐1‐phenylethyl)]phosphoramidite; 2b : P* = (S_a,R,R)‐ 1b = (1S_a)‐[1,1′‐binaphthalene]‐2,2′‐diyl bis[(1R)‐(1‐(1‐naphthalen‐1‐yl)ethyl]phosphoramidite) with (Et₃O)[PF₆] or Tl[PF₆] gives the cationic, 18‐electron complexes dichloro(η⁶‐p‐cymene){(1S_a)‐[1,1′‐binaphthalene]‐2,2′‐diyl {(1R)‐1‐[(1,2‐η)‐phenyl]ethyl}[(1R)‐1‐phenylethyl]phosphoramidite‐κP}ruthenium(II) hexafluorophosphate ( 3a ) and [Ru(S)]‐dichloro(η⁶‐p‐cymene){(1S_a)‐[1,1′‐binaphthalene]‐2,2′‐diyl {(1R)‐1‐[(1,2‐η)‐naphthalen‐1‐yl]ethyl}[(1R)‐1‐(naphthalen‐1‐yl)ethyl]phosphoramidite‐κP)ruthenium(II) hexafluorophosphate ( 3b ), which feature the η²‐coordination of one aryl substituent of the phosphoramidite ligand, as indicated by ¹H‐, ¹³C‐, and ³¹P‐NMR spectroscopy and confirmed by an X‐ray study of 3b . Additionally, the dissociation of p‐cymene from 2a and 3a gives dichloro{(1S_a)‐[1,1′‐binaphthalene]‐2,2′‐diyl [(1R)‐(1‐(η⁶‐phenyl)ethyl][(1R)‐1‐phenylethyl]phosphoramidite‐κP)ruthenium(II) ( 4a ) and di‐μ‐chlorobis{(1S_a)‐[1,1′‐binaphthalene]‐2,2′‐diyl [(1R)‐1‐(η⁶‐phenyl)ethyl][(1R)‐1‐phenylethyl]phosphoramidite‐κP}diruthenium(II) bis(hexafluorophosphate) ( 5a ), respectively, in which one phenyl group of the N‐substituents is η⁶‐coordinated to the Ru‐center. Complexes 3a and 3b catalyze the asymmetric cyclopropanation of α‐methylstyrene with ethyl diazoacetate with up to 86 and 87% ee for the cis‐ and the trans‐isomers, respectively.     

Synthesis, complexation behavior and application of a new diphosphite ligand in rhodium-catalyzed hydroformylation

Oxidative coupling of 3-(3-tert-butyl-4-hydroxyphenyl)propionic acid methyl ester (2) gave dimethyl 3,3′-(5,5′-di-tert-butyl-6,6′-dihydroxybiphenyl-3,3′-diyl)-dipropionate (1c), which upon phosphorylation/transesterification with a phosphochloridite derived from (R)-binaphthol, formed the new unsymmetrical binaphthol-bridged diphosphite 4. A rhodium catalyst based on 4 as ligand gave predominantly iso-selectivity in the hydroformylation of selected styrenes but opposite regioselectivity with 2,6-disubstituted derivatives. New chelate metal complexes (acac)RhL, PdCl₂L and PtCl₂L have been synthesized by reacting 4 with (acac)Rh(CO)₂, PdCl₂(MeCN)₂ and PtCl₂(COD), respectively. The structure of obtained compounds is determined based on ¹H, ¹³C, ³¹P and ¹⁹⁵Pt NMR spectroscopy and mass spectrometry data.     

Electrochemical sensors based on ionophores: Current state, trends, and prospects

The review considers ionophore-based electrochemical sensors (ion-selective electrodes). In general the progress in the field is subdivided in two distinctly different trends: (1) an extensive development (enhancing of the list of ions whose concentration can be selectively measured with the corresponding new sensors) and (2) an intensive development (improvement of the analytical capabilities of already known sensors). Recent articles (mostly published after the year 2000) describing the ionophore-based ion-selective electrodes are classified and briefly characterized from this viewpoint.     

Asymmetric Ir-catalyzed hydrogenation of 1,3-dihydro-2<Emphasis Type="Italic">H</Emphasis>-1,5-benzodiazepin-2-ones using phosphoramidites

A series of phosphoramidite ligands was tested in the asymmetric hydrogenation of 4-arylsubstituted 1,3-dihydro-2H-benzodiazepine-2-ones and up to 52% ee was achieved. The effects of various factors (solvents, hydrogen pressure, and addition of phosphine ligands) on the hydrogenation were studied.     

Reactions of chiral phosphoramidites with complexes Pd(COD)Cl2 and Pt(COD)Cl2

Reactions of phosphoramidites based on (−)-ephedrine and [(1S)-endo]-(−)-borneol with the complexes M(COD)Cl₂ (M is Pd or Pt, and COD is cycloocta-1,5-diene) were studied. The formation ofcis andtrans complexes of the general formulas MCl₂L₂ and M₂Cl₂(μ-Cl)₂L₂ was observed. The structures of the resulting compounds were established by³¹P,¹³C, and¹⁹⁵Pt NMR and IR spectroscopy and by plasma desorption mass spectrometry. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1627–1630, August, 1998.     

Ion-selective electrodes under galvanostatic polarization conditions

The application of ion-selective electrodes (ISE) with ionophore-based membranes under galvanostatic polarization conditions is briefly reviewed. The possibilities offered by polarization for expanding the working range of ISE and for varying their selectivity and the type of electrode response (cationic or anionic) are discussed.     

Platinum and rhodium complexes with isoleucinol-based bi- and tricyclic hydrophosphoranes

The complex formation of bi- and tricyclic hydrophosphorane derivatives of isoleucinol with [Pt(COD)Cl₂], [Rh(CO)₂Cl]₂, and [Rh(THF)₂(COD)]⁺BF₄ ^– (COD is cycloocta-1,5-diene) was investigated. In all cases, bicyclic hydrospirophosphorane selectively forms the metal chelates [M(²-PN)(X)Cl] (M = Pt, X = Cl; M = Rh, X = CO) and [Rh(²-PN)(COD)]⁺BF₄ ^–. («» denotes the residue of the hydrospirophosphorane ligand, which does not contain the P and N atoms). In addition, tricyclic hydrophosphorane (L) generates the phosphoranide complexes [Pt(¹-L)(COD)Cl]⁺Y^– (Y = Cl or BF₄). The structures of the new compounds were established by IR spectroscopy, ³¹P, ¹³C, ¹H, ²H, ¹¹B, ¹⁹F, and ¹⁹⁵Pt NMR spectroscopy, and plasma-desorption and electrospray ionization mass spectrometry. The possible mechanism of coordination of hydrophosphoranes is discussed.     

Chiral amido- and diamidophosphites with a peripheral pyridine ring in Pd-catalyzed asymmetric allylation

New chiral amidophosphite and diamidophosphite ligands with exocyclic pyridyl-containing substituents were obtained. Their efficiency in the Pd-catalyzed enantioselective allylic substitution was compared: in the sulfonylation of (E)-1,3-diphenylallyl acetate with sodium p-toluenesulfinate, the ee can reach 77%; its alkylation with dimethyl malonate and amination with pyrrolidine gave up to 80% and 74% ee, respectively. The asymmetric alkylation of cinnamyl acetate with ethyl 2-oxocyclohexanecarboxylate can provide to 68% ee. The complexation of zinc(ii) 5,10,15,20-tetraphenylporphyrinate with diamidophosphite ligand and its influence on conversion and enantioselectivity of the process were studied.