Solvent,ligand and temperature effects on the rates of reactions of cis-[PdCl2(CNR)(L)] with secondary amines

The kinetics of the reaction of cis-[PdCl₂(CN-p-C₆H₄Cl)(PPh₃)] with N-methylaniline yielding the carbene derivative cis-[PdCl₂ {C(NH-p-C₆H₄Cl)NMePh} (PPh₃)] have been studied in various solvents such as acetone, 1, 4-dioxane, 1,2-dichloroethane, and benzene. Overall rates for the stepwise process increase with decreasing ability of the solvent to form hydrogen bonds with the attacking amine. A kinetic study is also reported for the reactions of N-methylaniline with cis- [PdCl₂(CN-p-C₆H₄Me)(L)] in 1,2-dichloroethane (L = P(OMe)₃, P(OMe)₂Ph, PPh₃. PMePh₂, PMe₂Ph, PEt₃, PCy₃). The cis ligand L affects reaction rates through both steric and electronic factors. The nucleophilic attack of the amine on the CN carbon atom of coordinated isocyanide is favoured by low steric requirements and high π-acceptor ability of L. The activation parameters for the bimolecular nucleophilic attack when L = PPh₃ are △H^≠₂ = 9.8 ± 0.7 kcal/mol and △S^≠₂ = — 30 ± 2 e.u.     

Phosphin-stabilisierte carbonylnitrosylvanadium-verbindungen: Darstellung und spektroskopische eigenschaften

Numerous new complexes of the type V(CO)₅_n(NO)L_n, have been prepared either by nitrosylation of [V(CO)₆_nL_n]^?(n  2, 3) with NOX (X  Cl, BF₄) and [Co(NO)₂Br]₂, resp., or by reaction of L with “V(CO)₅NO” generated in situ. The compounds comprise n  1: L  PPh₃, PMe₂H, P(OMe)₃ and Ph₂PCH_2?PPh₂ (dppm); n  2: L₂2  2 PMe₂H, 2 PMe₃, 2 P(OMe)₃, dppm, Ph₂P(CH₂)_2?PPh₂, Ph₂P(CH₂)₃,PPh₂, Me₂P(CH₂)₂PMe₂, Ph₂As(CH₂)₂AsPh₂, o_?C₆H₄(AsMe₂)₂ (diars) and o_?C₆H₄(AsPh₂)PPh₂; n  3: L₃  1.5 diars and CH₃C(CH₂PPh₂)₃. IR (CO and NO stretching region) and ⁵¹V NMR spectra are discussed; for n  2 and 3, the positions of the arsine and phosphine ligands relative to NO are either cis for all the ligand functions (arsines) or cis/trans.     

Cumulated double bond systems as ligands : IV. 1H and 13C NMR studies of the intra- and inter-molecular exchange processes of cationic dialkylsulfurdiimine compounds of RhI,IrI and PtII

The preparation and properties are described of trans-[(Ph₃P)₂(CO)M(RNSNR)] [ClO₄] (M  Rh^I, Ir^I; R  Me, Et, i-Pr, t-Bu) and of cis- or trans-[L₂Pt(RNSNR)X] [ClO₄] (X  Cl^?, L  Et₂S, PhMe₂As, PhMe₂P, R  Me, t-Bu; X  CH₃, L  PhMe₂P, R  Me).¹H and ¹³C NMR data show the existence of various isomers in solution which may interconvert via intra- and inter-molecular exchange processes. A general reaction scheme for the intramolecular exchange processes is discussed.     

Synthesis and structural properties of a series of pentacoordinate rhodium nitrosyl complexes: Crystal and molecular structures of cis-dibromonitrosylbis(methoxydiphenylphosphine)rhodium and trans-dibromonitrosylbis(iso-propoxydiphenylphosphine)rhodium

The pentacoordinate rhodium nitrosyl complexes [RhBr₂(NO)L₂ [L = P(OPh)₂Ph, P(OMe)Ph₂ or P(OPrⁱ)Ph₂] have been synthesized and the structures of [RhBr₂(NO){P(OMe)Ph₂}₂] and [RhBr₂(NO){P(OPrⁱ)Ph₂}₂] have been determined X-ray crystallographically. Both of these latter compounds are tetragonal pyramidal with the nitrosyl group apical. The methoxydiphenylphosphine ligands in [RhBr₂(NO){P(OMe)Ph₂}₂] are cis-disposed whereas the larger cis-propoxydiphenylphosphine ligands in [RhBr₂(NO){P(OPrⁱ)Ph₂}₂] are mutually trans. The nitrosyl group in trans-[RhBr₂(NO){P(OPrⁱ)Ph₂}₂] eclipses an Rh-P axis but in cis-[RhBr₂(NO){P(OMe)Ph₂}₂] it is staggered with respect to the P-Rh-P linkage. The isomeric behaviour of nitrosyl complexes of type [RhX₂(NO)L₂] (X = halogen, L = phosphorus donor ligand) is rationalized in terms of the size of the ligand L.     

Substituted cyclopentadienyl complexes: II. 13C NMR spectra of some [(η5-C5H4Me)Fe(CO)(L)I] complexes

The ¹³C {¹H} NMR spectra of a series of complexes [(η⁵-C₅H₄Me)Fe(CO)(L)I] (L  t-BuNC, P(OMe)₃, PMe₃, PMe₂Ph, PMePh₃, PPh₃ and P(C₆H₁₁)₃) have been recorded and the five cyclopentadienyl resonances assigned to ring carbon atoms by means of CH correlated spectra. It has been observed that the C atoms ortho to the ring methyl group (C(2) and C(5)) as well as the quaternary C atom are always coupled to the ligand P atom. A correlation between the chemical shift difference Δ(C(2) – C(5)) and the Tolman cone angle, θ, has also been established.     

Binuclear organometallic compounds VIII. Oxidative addition of Si-H or Si-Cl compounds to low valent Fe, Co, or Ni complexes stabilised by mono- or bi-dentate phosphines

The reactions of [(Ph₃P)₄Ni], [(Ph₃P)₃CoN₂], [(dp)₂Ni], [(dp)₂CoH], [(dp)₂Fe(C₂H₄)] or [(dp)₂FeH₂] (dp = Ph₂PCH₂CH₂Ph₂P) with Ph_nSiCl_4-n (n = 1, 2, or 3), Ph_nSiH_4-n, X₃SiH (X = Cl or Et), or R₂ClSiH (R = Ph or Me) have been investigated. Solid complexes were isolated which, for the most part, were insoluble in non-polar solvents. Assignments of structures are therefore incomplete, and are based on microanalysis, IR spectra, analogies with established reactions, and (in some cases) chemical degradation. Evidence is presented for the following: (i) for Ni^II, products from [(Ph₃P)₄Ni] and HSiXX′X″ (XX′X″ = Ph₃, Ph₂H or PhH₂), the cyclic [(Ph₃P)₂NiSiCl₂]₂, and the five-coordinate [(dp)₂-NiX]⁺[SiCl₃]^- (X = H or Cl₃Si); (ii) for Co^III, the six-coordinate cis-octahedral [(dp)₂CoH₂]⁺ [SiXX′X″]^- (XX′X″ = Cl₃, Cl₂Me, ClMe₂, or ClPh₂); and for Fe^II, the four-coordinate [(dp)FeH(SiCl₃)] and the six-coordinate [(dp)₂Fe(X)SiCl₃] (X = H, Cl, or Cl₃Si).     

Complexes containing phosphorus lignads—161: New phosphinite,phosphonite and phosphite derivatives of ruthenium,osmium and iridium

The complexes [MHCl(CO)(PPh₃)₃] (M = Ru or Os) readily undergo substitution at the site trans to the hydride ligand to afford phosphinite-, phosphonite-, or phosphite-containing products [MHCI(CO)(PPh₃)₂L] [L = P(OR)Ph₂, P(OR)₂Ph or P(OR)₃ respectively; R = Me or Et]. The ruthenium complexes alone undergo further substitution to afford complex cations [RuH(CO)(PPh₃)_nL_4?n]⁺ [n = 2, L = P(OMe)₃; n = 1, L = P(OR)₃; n = 0, L = P(OR)₂Ph or P(OR)Ph₂] which were isolated and characterised as their tetraphenylborate salts. Synthesis of the cationic complexes [IrHL₅][BPh₄]₂ [L = P(OR)₃, R = Me or Et] is also reported. Stereochemical assignments based on NMR data are given, and second order ³¹P and high field ¹H NMR patterns are analysed.     

Syntheses and spectra of triphenyltin heteroarenethiolates: Crystal structures of triphenyltin 1-methyltetrazole-5-thiolate and triphenyltin benzoxazole-2-thiolate

Reactions between Ph₃SnCl and the sodium salts of 5-mercapto-1-methyltetrazole (MTS-H), 2-mercaptobenzoxazole (MBZ-H), 2-mercaptobenzothiazole (MBT-H) and 2-mercapto-1-methylimidazole (MMI-H) gave Ph₃Sn(MTS) (5: R=Ph, R′=Me), Ph₃Sn(MBZ) 6, Ph₃Sn(MBT) 7 and Ph₃Sn(MMI) 8, respectively. Characterisation has been carried out for all compounds by IR, Mössbauer, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy as well as by X-ray crystallography for (5: R=Ph, R′=Me) and 6. Both (5: R=Ph, R′=Me) and 6, in the solid state, have cis-trigonal bipyramidal geometries due to intramolecular Sn–N(2) interactions. Mössbauer data for 7 was interpreted as indicating a similar cis-trigonal bipyramid geometry. The chelating ability of nitrogen-containing heteroarenethiolato groups, based on the strength of Sn–N inter-molecular bonds in Ph₃SnS-heteroarenes, decreases in the sequence: pyridine-2-thiolato>pyrimidine-2-thiolato>1-methylimidazole-2-thiolato>benzoxazole-2-thiolato>1-methyltetrazole-5-thiolato>1-phenyltetrazole-5-thiolato. On dissolution, the Sn–N interactions in 5–8 undergo at least partial breakage.     

Cyclopentadienylcobalt Complexes Containing Two Phosphine Ligands

The ionic complexes [C₅H₅Co(L)(Ph₂PMe)I]⁺ [I]^- (L = Ph₃P and Ph₂PMe) were prepared by the reactions of cyclopentadienyl(triphenylphosphine)cobalt and cyclopentadienyl(methyldiphenylphosphine)cobalt diiodides with methyldiphenylphosphine. The treatment of these complexes with sodium tetraphenylborate results in the formation of [C₅H₅Co(L)(Ph₂PMe)I]⁺[BPh₄]^- compounds.     

Zur reaktion von metall-koordiniertem kohlenmonoxid mit yliden: XI. Einige neuartige η1-vinyl-komplexe des eisens durch deprotonierung kationischer carbenkomplexe mit trimethyl(methylen)phosphoran

Novel η¹-vinyl complexes of the type Cp(CO)(L)FeC(OMe)C(R)R′ (R = R′ = H, Me; R = H, R′ = Me; L = Me₃P, Ph₃P) are obtainied via methylation of the acyl complexes Cp(CO)(L)FeC(O)R (R = Me, Et, i-Pr) with MeOSO₂F and subsequent deprotonation of the resulting carbene complexes [Cp(CO)(L)FeC(OMe)R]SO₃F with the phosphorus ylide Me₃PCH₂. The same procedure can be applied for the synthesis of the pentamethylcyclopentadienyl derivative C₅Me₅(CO)(Me₃P)FeC(OMe)CH₂, while treatment of the hydroxy or siloxy carbene complexes [Cp(CO)(L)FeC(OR)Me]X (R = H, Me₃Si; X = SO₃CF₃) with Me₃CH₂ results in the transfer of the oxygen bound electrophile to the ylidic carbon. Some remarkable spectroscopic properties of the new complexes are reported.     

Addition des O'Donnell Reagenzes [Ph2C=NCHCO2Me]– an π-koordinierte,ungesättigte Kohlenwasserstoffe in [(C6H7)Fe(CO)3]+, [(C7H9)Fe(CO)3]+, [(C7H7)M(CO)3]+ (M = Cr,Mo) und [(C2H4)Re(CO)5]+. α-Aminosäuren mit metallorganischen Seitenketten

Metal Complexes of Biologically Important Ligands. CXVII [1] Addition of the O'Donnell Reagent [Ph₂C=NCHCO₂Me]^– to Coordinated, Unsaturated Hydrocarbons of [(C₆H₇)Fe(CO)₃]⁺, [C₇H₉Fe(CO)₃]⁺, [(C₇H₇)M(CO)₃]⁺ (M = Cr, Mo), and [(C₂H₄)Re(CO)₅]⁺. α-Amino Acids with Organometallic Side Chains The addition of [Ph₂C=NCHCO₂Me]^– to [(C₆H₇)Fe(CO)₃]⁺, [(C₇H₉)Fe(CO)₃]⁺, [(C₇H₇)M(CO)₃]⁺ (M = Cr, Mo) and [(C₂H₄)Re(CO)₅]⁺ gives derivatives of α-amino acids with organometallic side chains. The structure of [(η⁴-C₆H₇)CH(N=CPh₂)CO₂Me]Fe(CO)₃ was determined by X-ray diffraction. From the adduct of [Ph₂C=NCHCO₂Me]^– and [(C₇H₇)Mo(CO)₃]⁺ the Schiff base of a new unnatural α-amino acid, Ph₂C=NCH(C₇H₇)CO₂Me, was obtained.     

Synthetic,Mechanistic, and Theoretical Studies on the Generation of Iridium Hydride Alkylidene and Iridium Hydride Alkene Isomers

Experimental and theoretical studies on equilibria between iridium hydride alkylidene structures, [(Tp^Me2)Ir(H){?C(CH₂R)ArO }] (Tp^Me2=hydrotris(3,5‐dimethylpyrazolyl)borate; R=H, Me; Ar=substituted C₆H₄ group), and their corresponding hydride olefin isomers, [(Tp^Me2)Ir(H){R(H)C? C(H)OAr}], have been carried out. Compounds of these types are obtained either by reaction of the unsaturated fragment [(Tp^Me2)Ir(C₆H₅)₂] with o‐C₆H₄(OH)CH₂R, or with the substituted anisoles 2,6‐Me₂C₆H₃OMe, 2,4,6‐Me₃C₆H₂OMe, and 4‐Br‐2,6‐Me₂C₆H₂OMe. The reactions with the substituted anisoles require not only multiple C? H bond activation but also cleavage of the Me? OAr bond and the reversible formation of a C? C bond (as revealed by ¹³C labeling studies). Equilibria between the two tautomeric structures of these complexes were achieved by prolonged heating at temperatures between 100 and 140 °C, with interconversion of isomeric complexes requiring inversion of the metal configuration, as well as the expected migratory insertion and hydrogen‐elimination reactions. This proposal is supported by a detailed computational exploration of the mechanism at the quantum mechanics (QM) level in the real system. For all compounds investigated, the equilibria favor the alkylidene structure over the olefinic isomer by a factor of between approximately 1 and 25. Calculations demonstrate that the main reason for this preference is the strong Ir–carbene interactions in the carbene isomers, rather than steric destabilization of the olefinic tautomers.     

Metal dimers as catalysts : III. The reaction between Fe(CO)5, and group V donor ligands in the presence of [(η5-C5H4R)Fe(CO)222]2 (R  H,Me) and [(η5-C5Me5)Fe(CO)2]2 as catalyst

The reaction between Fe(CO)₅, and group V donor ligands L, (L  PPh₃, AsPh₃, SbPh₃, PMePh₂, PMe₂Ph, Asme₂Ph, P(C₆H₁₁)₃, P(n-Bu)₃, P(i-Bu)₃, P(OPh)₃, P(OEt)₃, P(OMe)₃) in the presence of [(η⁵-C₅Me₅Fe(CO)₂]₂ (R  H, Me) or [(η⁵-C₅Me₅)Fe(CO)₂]₂ as catalyst in refluxing toluene, rapidly gives the complexes Fe(CO)₄L in yields > 85%. The reaction rate is essentially independent of the nature of L for [(η₅-C₅Me₅)Fe(CO)₂]₂ as catalyst. For the other catalysts, the rate is influenced predominantly by the steric properties of L. These results are interpreted in terms of the interaction between the catalyst and the ligand L to give derivatives of the type (η⁵-C₅H₄R)₂Fe₂,(CO)₃,(L). These derivatives were also found to catalyse the reaction between Fe(CO)₅, and L. The complexes [(η-C₅H₄R)Fe(CO)₂]₂ (R  H, Me) and [(η⁵-C₅Me₅)Fe(CO)₂]₂ also catalyse the reaction between Mn₂(CO)₁₀ and PPh₃ to give Mn₂(CO)₈- PPh₃)₂ in > 80% yield.     

The 1H NMR spectra of methylmethoxyaluminium chloride and methylmethoxyaluminium iodide

It has been shown by means of ¹H NMR, IR and cryometrical measurements that, with oxygen bridges, Me(OMe)AlCl and Me(OMe)AII are trimers in solutions.Two isomers, cis and trans, are present, which are responsible for the multiple ¹H NMR spectra. The proton signals of MeAl and OMe groups are assigned in each isomer.     

Die Reaktion von Ph3AsCl2 mit Acetonitril. Kristallstrukturen von [Ph3AsNC(Me)C(AsPh3)CN]+Cl– und des Palladium‐Molekülkomplexes [Ph3AsNC(Me)C(AsPh3)CN–PdCl3]

The Reaction of Ph₃AsCl₂ with Acetonitrile. Crystal Structures of [Ph₃AsNC(Me)C(AsPh₃)CN]⁺Cl^– and of the Palladium Molecular Complex [Ph₃AsNC(Me)C(AsPh₃)CN–PdCl₃] In the presence of potassium hydride the reaction of Ph₃AsCl₂ with acetonitrile leads to [Ph₃AsNC(Me) · C(AsPh₃)CN]⁺Cl^– ( 1 ), which is characterized by its infrared spectrum and by a crystal structure analysis. 1 can be explained as an insertion reaction of acetonitrile into an ylidic As–C bond of the primarily formed [(Ph₃As)₂CCN]Cl. 1 : Space group P1, Z = 2, lattice dimensions at –70 °C: a = 991.9(1), b = 1255.2(1), c = 1381.3(1) pm, α = 81.64(1)°, β = 80.12(1)°, γ = 78.17(1)°; R₁ = 0.051. 1 reacts with palladium(II) chloride to give the molecular complex [Ph₃AsNC(Me)C(AsPh₃)CN–PdCl₃] ( 2 ) with zwitterionic structure. The fragment {PdCl₃^–} is terminally bonded at the nitrogen atom of the CCN group of the cation of 1 in a linear arrangement CCNPd. 2 · CH₃CN: Space group P2₁, Z = 2, lattice dimensions at –90 °C: a = 1079.2(1), b = 1261.5(1), c = 1560.9(1) pm; β = 110.20(1)°; R₁ = 0.0283.     

Trans --> cis isomerization of trans-[(dppm)2Ru(H)(L)][BF4] (L = P(OR)3) complexes: preparation of cis-[(dppm)2Ru(eta2-H2)(L)][BF4]2

A series of new dicationic dihydrogen complexes of ruthenium of the type cis-[(dppm)(2)Ru(eta(2)-H(2))(L)][BF(4)](2) (dppm = Ph(2)PCH(2)PPh(2); L = P(OMe)(3), P(OEt)(3), PF(O(i)Pr)(2)) have been prepared by protonating the precursor hydride complexes cis-[(dppm)(2)Ru(H)(L)][BF(4)] (L = P(OMe)(3), P(OEt)(3), P(O(i)Pr)(3)) using HBF(4).Et(2)O. The cis-[(dppm)(2)Ru(H)(L)][BF(4)] complexes were obtained from the trans hydrides via an isomerization reaction that is acid-accelerated. This isomerization reaction gives mixtures of cis and trans hydride complexes, the ratios of which depend on the cone angles of the phosphite ligands: the greater the cone angle, the greater is the amount of the cis isomer. The eta(2)-H(2) ligand in the dihydrogen complexes is labile, and the loss of H(2) was found to be reversible. The protonation reactions of the starting hydrides with trans PMe(3) or PMe(2)Ph yield mixtures of the cis and the trans hydride complexes; further addition of the acid, however, give trans-[(dppm)(2)Ru(BF(4))Cl]. The roles of the bite angles of the dppm ligand as well as the steric and the electronic properties of the monodentate phosphorus ligands in this series of complexes are discussed. X-ray crystal structures of trans-[(dppm)(2)Ru(H)(P(OMe)(3))][BF(4)], cis-[(dppm)(2)Ru(H)(P(OMe)(3))][BF(4)], and cis-[(dppm)(2)Ru(H)(P(O(i)Pr)(3))][BF(4)] complexes have been determined.     

<Emphasis Type="Italic">cis</Emphasis>-Tetra[(organo)(trimethylsiloxy)]cyclotetrasiloxanes: Synthesis and mesomorphic properties

Hydrolytic condensation of organotrialkoxysilanes RSi(OR′)₃ (R = Me, Et, Pr, CH=CH₂; R′ = OMe, OEt) in the presence of sodium and/or potassium hydroxide gave new alkali organosiloxanolates {(M⁺)₄[RSi(O)O⁻]₄}·nL (R = Me, Et, Pr, CH=CH₂; M = Na, K; L = R′OH, H₂O) in which the main structural fragment is the cyclotetrasiloxanolate fragment cis-[RSi(O)O⁻]₄. Based on these organosiloxanolates, a series of cis-tetra[(organo)(trimethylsiloxy)]cyclotetrasiloxanes was synthesized. For new cyclotetrasiloxanes, the thermotropic transitions and mesomorphic orderings were determined by differential scanning calorimetry, X-ray diffraction analysis, and polarization microscopy. In addition, new mesomorphic compounds were revealed. The character of thermotropic and time evolution of the phase state was found for a mixture of cis-tetra[ethyl(trimethylsiloxy)]-and cis-tetra[phenyl(trimethylsiloxy)]cyclotetrasiloxanes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 80–86, January, 2007.     

Synthèse de molécules organométalliques possédant un manganèse chiral

Synthesis of diastereoisomeric manganese complexes is described, starting from LMn(CO)₃, carbonyl substitutions gave LMn(CO)(PPh₃)[P(OMe)₃] (L = h⁵-C₅H₃, 1-CO₂Me, 3-Me).     

Synthesis of cationic dialkylgold(III) complexes: nature of the facile reductive elimination of alkane

A series of gold(III) cations of the type cis-[CH₃)₂AuL₂]⁺ X^? where L  Ph₃, PMePh₂, PMe₂Ph, PMe₃, AsPh₃, AsPh₃, SbPh₃, $\text{1}\text{2}$H₂NCH₂CH₂NH₂, $\text{1}\text{2}$ Ph₂PCH₂CH₂-PPh₂, $\text{1}\text{2}$ Ph₂AsCH₂CH₂AsPh₂, and $\text{1}\text{2}$o-C₆H₄(AsMe₂)₂ and X  BF₄^?, PF₆^?, ClO₄^?, and F₃CSO₃^? has been prepared. In addition, the cis complexes [(CH₃)(CD₃)-Au(PPh₃)₂]F₃CSO₃, [(C₂H₅)₂Au(PPh₃)₂]F₃CSO and [(n-C₄H₉)₂Au(PPh₃)₂]F₃-CSO₃ have been synthesized. All have been characterized by PMR, Raman and infrared spectroscopy. These [R₂AuL₂]X compounds yield only ethane, butane, or octane via reductive elimination, and no disproportionation is observed. The alkane eliminations have been studied in CHCl₃, CH₃Cl₂, and CH₃COCH₃ solution as a function of temperature, concentration of the complex, and concentration of added ligand L. Elimination is fastest when L is bulky (PPh₃ > PMePh₂ > PMe₂Ph > PMe₃), decreases in the sequence SbPh₃ > AsPh₃ > PPh₃, is slow with chelating ligands, is inhibited by excess ligand, and there is small anion effect as X is varied. As R is varied, the rate of elimination decreases Bu ? Et > Me. An intramolecular dissociative mechanism is proposed which involves rapid elimination of alkane from an electron deficient dialkylgold(III) complex with nonequivalent gold—carbon bonds and produces the corresponding [AuL₂]X complex.     

Extraction of f-elements from nitric acid solutions with phosphoryl ketones

The extraction ability and selectivity of a series of phosphoryl ketones Ph₂P(O)CH₂C(O)Me, and Ph₂P(O)CRR’CH₂C(O)Me (R = H, Me; R’ = H, Me, n-C₅H₁₁, Ph, 2-thienyl, 2-furyl) towards trivalent lanthanides (La^III, Nd^III, Ho^III, Yb^III) and actinides (U^VI, Th^IV) were studied. The efficiency and selectivity of the new ligands in the extraction of f-elements from nitric acid solutions into chloroform were compared to those of model phosphine oxide Ph₂P(O)Bu and known extractants: tributyl phosphate (BuO)₃P(O), trioctylphosphine oxide (C₈H₁₇)₃P(O), and carbamoylmethyl phosphine oxide Ph₂P(O)CH₂C(O)NBu₂.