- A Lewis Base Nucleofugality Parameter, NFB, and Its Application in an Analysis of MIDA-Boronate Hydrolysis Kinetics
-
The kinetics of quinuclidine displacement of BH3 from a wide range of Lewis base borane adducts have been measured. Parameterization of these rates has enabled the development of a nucleofugality scale (NFB), shown to quantify and predict the leaving group ability of a range of other Lewis bases. Additivity observed across a number of series R′3-nRnX (X = P, N; R′ = aryl, alkyl) has allowed the formulation of related substituent parameters (nfPB, nfAB), providing a means of calculating NFB values for a range of Lewis bases that extends far beyond those experimentally derived. The utility of the nucleofugality parameter is explored by the correlation of the substituent parameter nfPB with the hydrolyses rates of a series of alkyl and aryl MIDA boronates under neutral conditions. This has allowed the identification of MIDA boronates with heteroatoms proximal to the reacting center, showing unusual kinetic lability or stability to hydrolysis.
- García-Domínguez, Andrés,Gonzalez, Jorge A.,Leach, Andrew G.,Lloyd-Jones, Guy C.,Nichol, Gary S.,Taylor, Nicholas P.
-
supporting information
(2022/01/04)
-
- Reduction of tertiary phosphine oxides to phosphine-boranes using Ti(Oi-Pr)4/BH3-THF
-
A new method for reduction of tertiary phosphine oxides leading to the formation of tertiary phosphine-boranes has been developed. The BH3-THF/Ti(Oi-Pr)4 reducing system enables conversion of triaryl, diarylalkyl and trialkylphosphine oxides directly to their borane analogues in good to high yields. In contrast to the previously reported protocols, the presence of activating groups in the structure of starting material is not necessary for the reaction to occur. The reaction is highly stereoselective and proceeds with predominant retention of configuration at the phosphorus atom. A plausible mechanism of reduction of the P[dbnd]O bond by BH3-THF/Ti(Oi-Pr)4 has been proposed.
- Sowa, Sylwia,Pietrusiewicz, K. Micha?
-
supporting information
(2021/03/17)
-
- Synthesis of Molybdenum(VI) Neopentylidene Neopentylidyne Complexes
-
Mo(C-t-Bu)(CH-t-Bu)(Cl)(PMe2Ph)2 (1) was prepared as off-white crystals in 26% yield through addition of 2.5 equiv of Mg(CH2-t-Bu)2 to Mo(O)[OC(CF3)3]4 in diethyl ether followed by 3 equiv of PMe2Ph and a workup that includes dichloromethane (the source of Cl). Compound 1 is largely a syn isomer initially that equilibrates to give approximately a 1:1 mixture of syn and anti isomers within 1-2 h. Compound 1 reacts with Li(3,5-dimethylpyrrolide) to give Mo(C-t-Bu)(CH-t-Bu)(η1-Me2Pyr)(PMe2Ph)2 (2a) as a pale yellow solid in 76% yield, and 2a reacts with Ph3SiOH to give a mixture of syn and anti Mo(C-t-Bu)(CH-t-Bu)(OSiPh3)(PMe2Ph)2 (3a) in 84% yield. All three compounds tend to lose PMe2Ph to give 14e monophosphine complexes with the formulas Mo(C-t-Bu)(CH-t-Bu)(X)(PMe2Ph) (X = Cl, Me2Pyr, or OSiPh3), none of which could be isolated. X-ray studies show the structures of 1, 2a, and 3a to be analogous with τ values of 0.45, 0.53, and 0.69, respectively.
- Tafazolian, Hosein,Schrock, Richard R.,Müller, Peter
-
supporting information
p. 2888 - 2891
(2019/08/30)
-
- Ir(III)-catalyzed direct C-H functionalization of arylphosphine oxides: A strategy for MOP-type ligands synthesis
-
Diazo compounds as coupling partners are efficiently applied to Ir(III)-catalyzed direct C-H functionalization of arylphos-phine oxides. Involving C-H activation, carbene insertion, and tautomerism, this reaction proceeds under mild conditions, thus proving an approach to the synthesis of MOP-type ligand precursor in a single step. The utility of this transformation has been further demonstrated in ligand synthesis as well as in the construction of phosphole framework.
- Liu, Zhong,Wu, Ji-Qiang,Yang, Shang-Dong
-
supporting information
p. 5434 - 5437
(2017/11/06)
-
- A study on the deoxygenation of trialkyl-, dialkyl-phenyl- and alkyl-diphenyl phosphine oxides by hydrosilanes
-
The deoxygenation of 1-alkyl-3-methyl-3-phospholene 1-oxides, which may be regarded as trialkyl phosphine oxides (R3PO), and the reduction of dialkyl-phenylphosphine oxides (R2PhPO) and methyl-diphenylphosphine oxide (MePh2PO) have been elaborated by applying user-friendly silanes, such as tetramethyldisiloxane (>SiH–O–HSin) under solvent-free, catalyst-free, and microwave (MW)-assisted conditions. New silanes of type Ar2SiH2, alkyl2SiH2, and Ar3SiH were also applied in a few cases. The reactivity of the phosphine oxides and the silanes could be mapped on the basis of our experimental data.
- Kovács, Tamara,Urbanics, Anita,Csatlós, Flóra,Keglevich, Gy?rgy
-
-
- Br?nsted Acid Promoted Reduction of Tertiary Phosphine Oxides
-
Recently, Br?nsted acids, such as phosphoric acids, carboxylic acids, and triflic acid, were found to catalyze the reduction of phosphine oxides to the corresponding phosphines. In this study, we fully characterize the HCl, HOTf, and Me2SiHOTf adducts of triphenylphosphine oxide and find that the thermally stable adduct Ph3POH+OTf– is efficiently converted into triphenylphosphine at 100 °C in the presence of readily available hydrosiloxanes. Under the same reaction conditions, also Ph3POSiMe2H+OTf– selectively affords triphenylphosphine indicating that silylated phosphine oxides are likely intermediates in this process.
- Krachko, Tetiana,Lyaskovskyy, Volodymyr,Lutz, Martin,Lammertsma, Koop,Slootweg, J. Chris
-
p. 916 - 921
(2017/08/11)
-
- Organocatalyzed Reduction of Tertiary Phosphine Oxides
-
A novel selective catalytic reduction method of tertiary phosphine oxides to the corresponding phosphines has been developed. Notably, the reaction proceeds smoothly with low catalyst loadings of 1-5 mol% even at low temperature (70 C). Under the optimized conditions various phosphine oxides could be selectively reduced and the desired phosphines were usually obtained in excellent yields above 90%. Furthermore, we have developed a one-pot reaction sequence for the preparation of valuable phosphinborane adducts. Simple addition of BH3THF subsequent to the reduction step gave the desired adducts in yields up to 99%.
- Schirmer, Marie-Luis,Jopp, Stefan,Holz, Jens,Spannenberg, Anke,Werner, Thomas
-
supporting information
p. 26 - 29
(2016/01/25)
-
- The deoxygenation of phosphine oxides under green chemical conditions
-
The deoxygenation of a few diaryl-phenylphosphine oxides, dimethyl-phenylphosphine oxide, and 3-methyl-1-phenyl-3-phospholene 1-oxide was studied by phenylsilane, tetramethyldisiloxane (TMDS), and polymethylhydrosiloxane (PMHS) under conventional or microwave (MW) heating, in toluene or in the absence of any solvent at different temperatures. It was found that the deoxygenation with TMDS or PMHS under MW and solvent-free conditions may be the method of choice and provides a green chemical approach.
- Keglevich, Gy?rgy,Kovcs, Tamara,Csatls, Flra
-
p. 199 - 205
(2015/05/19)
-
- Highly efficient reduction of tertiary phosphine oxides and sulfides with amine-assisted aluminum hydrides under mild conditions
-
Reduction of tertiary phosphine oxides and sulfides into the corresponding phosphines with amine-assisted aluminum hydrides has been studied. The method is characterized by mild conditions, short reaction time, high efficiency, and expanded substrate scope. The new method is an alternative to the currently used methods of reducing phosphine oxides or recycling phosphines engaged in organic reactions.
- Yang, Shuyan,Han, Xinxin,Luo, Minmin,Gao, Jing,Chu, Wenxiang,Ding, Yuqiang
-
p. 1156 - 1160
(2015/06/30)
-
- Reactions of a tungsten alkylidyne complex with mono-dentate phosphines: Thermodynamic and theoretical studies
-
Addition of mono-dentate phosphines PMe3 and PMe2Ph to the W(VI) alkyl alkylidyne complex W(CH2SiMe3) 3(≡CSiMe3) (1) is reversible, each reaching equilibrium. Thermodynamic studies of the equilibria have been conducted, giving ΔH° = -10.0(1.1) kcal/mol and ΔS° = -23(4) eu for the addition of PMe3 and ΔH°′ = -3.0 (0.7) kcal mol -1 and ΔS°′ = -6(3) eu for the addition of PMe 2Ph, indicating that the addition is exothermic. The experimental measurement allows a benchmarking study to select a proper DFT method to describe the current system. Of the DFT methods tested, M06 has demonstrated superior performance in calculating binding energy of a bimolecular reaction. The calculated reaction pathways show that W(CH2SiMe 3)3(≡CSiMe3) (1) reacts with PR3 to form W(CH2SiMe3)3(≡CSiMe3)(PR 3) (PR3 = PMe3, 3a; PMe2Ph, 3b), and the adduct then undergoes α-H migration to form W(CH2SiMe 3)2(=CHSiMe3)2(PR3) (4a, 4b). 4a and 4b are found to be thermodynamically and kinetically stable intermediates. The calculations also suggest a pathway in the formation of the alkyl alkylidene alkylidyne complex W(CH2SiMe3)- (=CHSiMe3)(≡CSiMe3)(PR3)2 (5a).
- Chen, Ping,Dougan, Brenda A.,Zhang, Xinhao,Wu, Yun-Dong,Xue, Zi-Ling
-
-
- Coordination effects on electron distributions for rhodium complexes of the redox-active bis(3,5-di- tert -butyl-2-phenolate)amide ligand
-
New rhodium complexes of bis(3,5-di-tert-butyl-2-phenol)amine ([ONO cat]H3) were synthesized, and their electronic properties were investigated. These compounds were prepared by combining [ONOq]K and [(cod)Rh(μ-Cl)]2 in the presence of an auxiliary donor ligand to yield complexes of the type [ONO]RhLn (n = 3, L = py (1); n = 2, L = PMe3 (2a), L = PMe2Ph (2b), PMePh2 (2c), PPh3 (2d)). Single-crystal X-ray diffraction studies on [ONO]Rh(py)3 (1) revealed a six-coordinate, octahedral rhodium complex. In the case of [ONO]Rh(PMe3)2 (2a), X-ray diffraction showed a five-coordinate, distorted square-pyramidal coordination environment around the rhodium center. While 1 is static on the NMR time scale, complexes 2a-d are fluxional, displaying both rapid isomerization of the square-pyramidal structure and exchange of coordinated and free phosphine ligands. UV-vis spectroscopy shows stark electronic differences between 1 and 2a-d. Whereas 1 displays a strong absorbance at 380 nm with a much weaker band at 585 nm in the absorption spectrum, complexes 2a-d display an intense (ε > 104 M-1 cm-1), low-energy absorption band in the region 580-640 nm; however, in the cases of 2a and 2b, the addition of excess phosphine resulted in changes to the UV-vis spectrum indicating the formation of six-coordinate adducts [ONO]Rh(PMe3)3 (3a) and [ONO]Rh(PMe2Ph)3 (3b), respectively. The experimental and DFT computational data for the six-coordinate complexes 1, 3a, and 3b are consistent with their formulation as classical, d6, pseudo-octahedral, coordination complexes. In the five-coordinate complexes 2a-2d, φ-bonding between the rhodium center and the [ONO] ligand leads to a high degree of covalency and metal-ligand electron distributions that are not accurately described by formal oxidation state assignments.
- Szigethy, Géza,Shaffer, David W.,Heyduk, Alan F.
-
p. 12606 - 12618
(2013/02/22)
-
- Ni(acac)2/phosphine as an excellent precursor of nickel(0) for catalytic systems
-
The coordination of phosphine ligands to nickel acetylacetonate was studied in toluene solution, and the first X-ray structure of the unstable complex trans-[Ni(acac)2(PMe2Ph)2] has been reported. A convenient procedure was developed to generate Ni(0) species in situ in solution from a Ni(acac)2 precursor, and their application in catalysis was demonstrated. A study of the reaction mechanism has suggested that water may play an important role in the formation of zerovalent nickel species. The nature of the Ni(0) species was confirmed by trapping with Ph 2S2, and the structure of the resulting complexes trans-[Ni(SPh)2L2] was established by X-ray analysis for L = PMe2Ph, PMePh2, PBu3.
- Ananikov, Valentine P.,Gayduk, Konstantin A.,Starikova, Zoya A.,Beletskaya, Irina P.
-
p. 5098 - 5102
(2011/01/05)
-
- An acidity scale of tetrafluoroborate salts of phosphonium and iron hydride compounds in [D2]dichIoromethane
-
Equilibrium constants (K) for reactions between acids and the conjugate base forms of a number of phosphonium salts, [HPR3][BF4], and iron hydrides, [Fe(CO)3H(PR3)2][BF 4], in CD2Cl2 have been determined by means of 31P and 1H NMR spectroscopy at 20°C. The anchor compound chosen for pKCD2Cl2 determinations was [HPCy 3][BF4] with a pKCD2Cl2 value of 9.7, as assigned by literature convention (Cy: cyclohexyl). A continuous scale of pKCD2Cl2 values covering the range from 9.7 to -3 was created and correlated with the ΔH values reported by Angelici and co-workers and literature pKa values. The pKCD2Cl2 values for 15 other hydride or dihydrogen complexes of the iron group elements and of diethyl ether were also placed on this scale. The crystal structures of [Fe(CO) 3H(PCy2Ph)2][BF4] and [Fe(CO) 3(PCy2Ph)2] revealed that the frans-oriented, bulky, unsymmetrical phosphane ligands distort the equatorial plane of the complexes. The acidity of iron carbonyl hydrides is an important feature of the reactions of iron hydrogenase enzymes.
- Li, Tianshu,Lough, Alan J.,Morris, Robert H.
-
p. 3796 - 3803
(2008/02/08)
-
- Work-up-free deprotection of borane complexes of phosphines, phosphites, and phosphinites with polymer-supported amines
-
Borane complexes of phosphorus compounds, a very common oxidation-free relay for catalytic ligands (phosphines, phosphites, and phosphinites), can be easily deprotected by treatment with polymer-supported piperazine or N-methylpiperazine. Deprotection conditions have been optimized for the different types of phosphorus compounds, and the resulting solutions can be used without any intermediate work-up or purification process. Georg Thieme Verlag Stuttgart.
- Sayalero, Sonia,Pericàs, Miquel A.
-
p. 2585 - 2588
(2008/09/16)
-
- A novel mild deprotection method for phosphine-boranes
-
Treatment of phosphine-boranes with molecular sieves 4A in a mixture of an ethereal solvent and an alcohol provided deprotected free phosphines in quantitative yields. The phosphines can be obtained by a simple filtration/crystallization procedure in most cases. It should be noted that the current method is successfully applied to the deprotection of a phosphite-borane for the first time.
- Schroeder, Marc,Nozaki, Kyoko,Hiyama, Tamejiro
-
p. 1931 - 1932
(2007/10/03)
-
- Trimethylsilyl- and trimethylstannyldimethylphosphane - Convenient and versatile reagents for the synthesis of polyfluoroaryldimethylphosphanes
-
Trimethylsilyldimethylphosphane (Me3SiPMe2) and the corresponding tin compound (Me3SnPMe2) were used as reagents for the substitution of fluorine by the Me2P group in polyfluoroarenes C6F5X (X = F, H, Cl, CF3) and C5NF5. The reactions occur even under mild conditions (T= 0-20°C), either in benzene or without solvent, to give as a rule 4-X-1-(dimethylphosphano)tetrafluorobenzenes (XC6F4PMe2, 1-4) and 4-(dimethylphosphano)tetrafluoropyridine (C5NF4PMe2, 5), respectively, in yields between 75 and 95 %. In the case of C6F6, double substitution is also observed, which affords 1,4-bis(dimethylphosphano)tetrafluorobenzene (6). A very efficient route to the compounds XC6F4PMe2 (X=F, H, Cl, CF3) and C5NF4PMe2 was developed as a one-pot reaction of the corresponding fluoroarenes with tetramethyldiphosphane (P2Me4) and trimethyltin hydride (Me3SnH) at moderate temperatures. This process was tested for C6F6 and perfluorobiphenyl which gave C6F5PMe2 (1) and 4,4′-bis(dimethylphosphano)octafluorobiphenyl (7), respectively. The results, which included kinetic measurements that used the intensities of the 31P signals, revealed the influence of the substrate type on the rate of reaction in the sequence: C5NF5 > C6F5CF3 > C6F5Cl, C6F5PMe2 > C6F5H > C6F6? C6H5F. Ab initio calculations were carried out on the model reactions of pentafluoropyridine with silylphosphane, phosphane or phosphide to discriminate between possible reaction mechanisms. The novel phosphanes were characterised by spectroscopic investigations (NMR, MS), by preparation of the related thiophosphanes ArFP(=S)Me2 (8-14), their spectroscopic and analytic data and single crystal X-ray diffraction studies on five of these derivatives.
- Goryunov, Leonid I.,Grobe, Joseph,Shteingarts, Vitalij D.,Krebs, Bernt,Lindemann, Arno,Wuerthwein, Ernst-Ulrich,Mueck-Lichtenfeld, Christian
-
p. 4612 - 4622
(2007/10/03)
-
- Tertiary phosphine ligand-exchange reactions involving the M(Strictly equivalent to)M quadruply bonded complexes M2Cl4L4, where L = PMe3, PEt3, PBun3 or PMe2Ph
-
The reactions between M2Cl4L4 complexes and an excess of L or L′ (PMe3, PEt3, PBun3, PMe2Ph or PMePh2) have been studied in [2H8]toluene by 31P-{1H} NMR spectroscopy. The substitutions proceed in a stepwise manner wherein L′ displaces L, except for L′ = Me2PCH2CH2PMe2 (dmpe) which yields Mo2Cl4(dmpe-P)4. No tertiary phosphine in this series is capable of displacing PMe3 from a M2Cl4(PMe3)4 complex but by spin magnetization transfer the degenerate exchange involving Mo2Cl4(PMe3)4 and PMe3 (added in excess) can be detected. The complexes Mo2Cl4(PMe3)4 and Mo2Cl4(PEt3)4 in benzene showed no PMe3 for PEt3 scrambling at +50°C over several days despite the fact that Mo2Cl4(PMe3)4-n(PEt 3)n, where n = 2 or 3, are kinetically inert to ligand redistribution. In the presence of [2H5]pyridine Mo2Cl4(PMe3)4 and Mo2O4(PEt3)4 underwent tertiary phosphine scrambling at 25°C and in neat [2H5]pyridine Mo2Cl4(PMe3)4 revealed the formation of an equilibrium concentration of Mo2Cl4(PMe3)3(py) (py = pyridine) and free PMe3. Under similar conditions Mo2Cl4(PEt3)4 yielded an equilibrium mixture of Mo2Cl4(PEt3)3(py) and Mo2Cl4(PEt3)2(py)2 and free PEt3. From kinetics the ΔH? values are positive in the range +24 to +34 kcal mol-1 and the ΔS? values range from +12 to +28 cal K-1 mol-1. Collectively the data reported are consistent with an interchange dissociative mechanism, Id, wherein M-P bond breaking contributes significantly to the rate-determining step with related values of ΔH? being larger for M = W than M = Mo. The rate dependence on the entering ligand is clearly evident from temperature-dependent studies and leads to varying ΔS? values. The Id mechanism is proposed to involve pre-equilibria between M2Cl4L4 and the entering L′ in an axial site followed by rate-determining M-L displacement. In neat [2H5]pyridine this may be viewed as a solvent-assisted displacement. The present results are discussed in terms of earlier studies from which researchers inferred a simple dissociative process, D, involving M-PR3 bond rupture as the first and rate-determining step.
- Chisholm, Malcolm H.,McInnes, Jacqueline M.
-
p. 2735 - 2743
(2007/10/03)
-
- Synthesis and Conformational Behavior of 2-Phosphonio- and 2-Phosphinyl-1,3-dithianes. Operation of the Generalized Anomeric Effect in the S-C-P(+) System
-
A stereoselective preparation of various 2-phosphinyl- and 2-phosphonio-1,3-dithianes by desulfurization of the appropriate 2-thiophosphoryl-1,3-dithianes was described.The structure of the title compounds was studied by means of 1H, 13C, and 31P NMR methods.Configurational assignments were also based on chemical correlation and X-ray structure determination.Both the NMR studies of conformationally labile models and equilibration of diastereomeric compounds showed an increased preference of the phosphinyl and phosphonium groups for the axial orientation.Magnitude of the anomeric effect found varies in the range from ca. 6 kJ/mol in phosphines to more than 10 kJ/mol in phosphonium salts.The anomeric effect could stem from the ns-?*C-P hyperconjugative interaction.If phenyl groups are connected with phosphorus, overlap repulsion involving lone electron pairs of the endocyclic sulfur atoms and ?-electrons of phenyl rings should also be taken into account.The reverse anomeric effect was not observed.No manifestation of the exo anomeric effect in 2-phosphinyl-1,3-dithianes was found.
- Mikolajczyk, Marian,Graczyk, Piotr P.
-
p. 5190 - 5208
(2007/10/02)
-
- Synthesis and Carbonylation Studies on Methylpalladium(II) Complexes containing Chelating Pyridinecarboxylate Ligands: Dynamic Behaviour of the Ligands and Implications for the Carbonylation Mechanism
-
Methylpalladium complexes of the general formula were synthesised and the dynamic behaviour of the ligands pyca and L studied in detail.The ligands were found to undergo readily a variety of exchange reactions, clearly demonstrating their lability under mild conditions.The ligand exchange behaviour and data on rates of carbonylation for the palladium complexes led to a dissociative mechanism, requiring lability in both the ligand L and the chelate, being proposed for the CO insertion process.The methylpalladium complexes exist in solution as a mixture of cis and trans isomers.However the acyl complexes were found to occur only in the geometry with the phosphine cis to the acyl group.X-Ray crystal structures were obtained for the complexes > and .The complexes have distorted square-planar geometry: for the palladium complex, which is highly distorted, P-Pd-O(21) 97.3(1), P-Pd-C(01) 88.9(2), N-Pd-O(21) 78.4(2) and N-Pd-C(01) 95.9(2) deg and for the platinum complex P-Pt-O(21) 93.9(5), P-Pt-C(01) 95.1(9), N-Pt-O(21) 80.4(7) and N-Pt-C(01) 91(1) deg.
- Jin, Hong,Cavell, Kingsley J.,Skelton, Brian W.,White, Allan H.
-
p. 2159 - 2170
(2007/10/03)
-
- Two isomers of WCl3(PMe2Ph)3 and their potential for equilibration with W2Cl6(PMe2Ph)n
-
A new (comproportionation) synthesis of WCl3(PMe2Ph)3, as well as the coexistence of two structural isomers, is reported. These are characterized by 1H NMR spectroscopy and single-crystal X-ray diffraction. Equilibration of these two species is effected at 80°C, with mer converting completely to fac. It is not possible to convert the WCl3L3 (L = PMe2Ph) species to either of the known dimers W2Cl6Ln, (n = 3, 4). The mer → fac isomerization is shown to be catalyzed by WCl4L2 (but not by WCl2L4). The mechanism of the comproportionation synthesis of WCl3L3 strongly favors the mer isomer, and a mechanism is proposed to account for this. Photolysis of a mixture of [WCl3(PMe2Ph)2]2 in the presence of excess PMe2Ph completely converts the dimer to mer-WCl3(PMe2Ph)3. Mechanistic features which cause the stereoselectivity of this reaction are discussed. Cell parameters for fac-WCl3L3 (-165°C): a = 9.476(2) A?, b = 18.091 (5) A?, c = 9.185(2) A?, α = 98.62(1)°, β = 101.53(1)°, γ = 93.49(1)° with Z = 2 in space group P1. Cell parameters for mer WCl3L3 at -155°C, a = 16.031(3) A?, b = 10.297(1) A?, c = 17.913(3), β = 113.86(1)°, Z = 4, and space group P21/c.
- Rothfuss, Helmut,Barry, Jane T.,Huffman, John C.,Caulton, Kenneth G.,Chisholm, Malcolm H.
-
p. 4573 - 4577
(2008/10/08)
-
- Synthesis, reactivity and kinetic studies of bis(η5-cyclopentadienyl)titanium methylidene phosphine complexes
-
Syntheses of several bis(η5-cyclopentadienyl)titanium methylidene phosphine complexes are reported. The titanocene methylidene phosphine complexes are generated from thermolysis of titanocene metallacyclobutanes in the presence of excess phosphine. Spectral data and reactivity are consistent with a methylidene phosphine complex rather than an ylide complex. The titanocene methylidene phosphine complexes react with olefins to form metallacyclobutanes, alkynes to form metallacyclobutenes, and CO to form a ketene complex. The phosphine ligand is labile, and an equilibrium mixture is rapidly established if a second phosphine is added. The kinetics of this equilibration and the kinetics of the reaction of titanocene methylidene phosphine complexes with alkynes and olefins are reported. The reactions proceed by rate-determining loss of phosphine followed by rapid trapping of titanocene methylidene.
- Meinhart, James D.,Anslyn, Eric V.,Grubbs, Robert H.
-
p. 583 - 589
(2008/10/08)
-
- Cu(PMe3)4.
-
Alkylation of copper(II) acetate with dialkylmagnesium reagents in the presence of tertiary phosphines gives the colorless copper(I) alkyl species. With sterically small phosphines, the complexes are ionic and possess left bracket Cu(PR//3)//4 right bracket cations and left bracket CuR//2 right bracket anions; larger phosphines give electrically neutral CuR(PR//3)//3 coordination complexes. Solution NMR data indicate that reversible phosphine dissociation is a facile process for all of the complexes and that extensive ion pairing occurs in nonpolar solvents. The X-ray crystal structure of the dimethylcuprate complex has been determined.
- Dempsey,Girolami
-
p. 1208 - 1213
(2008/10/08)
-
- Preparation of Alkylmethylphenylphosphines by the Method of Hewertson and Watson
-
The reaction of C6H5(CH3)PNa with some alkyl halides in liquid ammonia was studied.The resulting phosphines were characterized by elemental analyses, NMR spectra, and by the reaction with trimethylsilyl azide giving trimethylsilylimino triorganophosphoranes. - Keywords: Alkylmethylphenylphosphines, N-Trimethylsilylimino Triorganophosphoranes, NMR Spectra
- Wolfsberger, Werner
-
p. 295 - 298
(2007/10/02)
-
- Phosphinocyclopentadienide via Cyclopentadienylphosphide
-
Lithiumorganyls RLi (R = Me, Bu, Ph) add to (PhP)5 in successive degradation and disproportionation equilibria depending on the ratio of the reactants.At -70 deg C (R = Me) disproportionation is blocked and (PhP)4R(-) and (PhP)3R(-) can be detected.With excess RLi monophosphides PhPR(-) are formed.CpNa with the help of a crown ether degrades (PhP)5 or substitutes cyanide from PhPCN(-) to give an equilibrium mixture of (PhP)nCp(-) anions, which stabilize by proton shifts: In case of n = 1 and 2 a shift from the Cp unit to the terminal phosphorus results in the formation of the phenylphosphino- and diphenyldiphosphino-cyclopentadienide anion, in case of n = 3 two proton shifts within the Cp unit result in a cyclopenteno-1,2,3-triphospholene allylic anion. - Keywords: Cyclophosphane, Cyclopentadienide, Nucleophilic Degradation, 31P NMR Spectra
- Schmidpeter, Alfred,Zirzow, Karl-Heinz
-
p. 977 - 983
(2007/10/02)
-
- Notes Unsymmetrical Bis(phosphorus) Compounds: Synthesis of Unsymmetrical Ditertiary Phosphines, Phosphine Oxides, and Diquaternary Phosphonium Salts
-
A convenient preparative route to the unsymmetrical bidentate phosphines R2P(CH2)nPPh2 (R=Me or Et; n=3 or 4) is described.This involves the synthesis of unsymmetrical diphosphonium salts, Br2, and diphosphine oxides, R2P(O)(CH2)nPPh2, as intermediates.The symmetrical ligand Et2P(CH2)3PEt2 was also prepared by the same route.New co-ordination complexes of manganese(II) with these ligands have been isolated.
- Benn, Roger F.,Briggs, Josie C.,McAuliffe, Charles A.
-
p. 293 - 296
(2007/10/02)
-
- STUDIES ON NUCLEOPHILIC ADDITIONS AT BRIDGING VINYL LIGANDS IN TRIOSMIUM CLUSTERS
-
The bridging vinyl clusters (R = H, Ph, or n-Bu) react with PMe2Ph to give the zwitterionic adducts which contain μ2-alkylidene ligands.The adducts are not formed so readily when R = Ph or n-Bu but
- Deeming, Antony J.,Manning, Peter J.
-
-
- PHOTOCHEMISTRY OF TRANSITION-METAL POLYHYDRIDES: DIMERIZATION OF OsH4(PMe2Ph)3 FOLLOWING PHOTODISSOCIATION OF DIHYDROGEN
-
UV (254 nm) photolysis of OsH4P3 (P PMe2Ph) proceeds, by photodissociation of H2, to give the transient OsH2P3.This species exchanges deuterium with C6D6, reacts with phosphine to give cis-H2OsP4, and with OsHxP3 to give Os2H2(μ-H)2P6, whose structure was determined by X-ray diffraction.This Os=Os dimer participates in a unique reversible (25 deg C) phosphine dissociation equilibrium to produce Os2H4P5, containing an OsOs bond.A structural analog of this dimer was produced by acidolysis of Os2H4P6 to give Os2H3P6+, which X-ray diffraction reveals to have aP3Os(μ-H)3OsP3+ structure.
- Green, Mark A.,Huffman, John C.,Caulton, Kenneth G.
-
p. C78 - C82
(2007/10/02)
-
- Basicities of Methyl-, Methylphenyl-, and Phenylphosphines in the Gas Phase
-
The relative gas-phase basicities of the methyl-, methylphenyl-, and phenylphosphines were measured with a pulsed electron high ion source pressure mass spectrometer.The kinetics leading to the equilibria and the equilibria B0H+ + B = B0 + BH+ were observed and the equilibrium constants K determined.These led to standard free energy changes ΔGo.For a constant B0 = Me3P, these were: B = Me2PhP, ΔGo = -2.5 kcal/mol; B = MePh2P, ΔGo = -3.2 kcal/mol; B = Ph3P, ΔGo ca. -3.2 kcal/mol.Also the vertical ionization potentials of the phosphorus lone pairs were measured by photoelectron spectroscopy.These were found to decrease in the order Me3P -> Ph3P as expected basicity changes.The observed increase of basicity with phenyl substitution in the gas phase is opposite to the order in solution where the basicity decreases in the order Me3P -> Ph3P.The latter must be due to adverse solvation of the phenylphosphonium ions.The observation that the gas-phase basicities increase when methyl is replaced by phenyl is very interesting.A decrease is observed for the analogous amines where the basicity of Me2PhN is lower than that of Me3N.Part of this difference of behavior can be attributed to stabilization in the phenylphosphonium ions by ?-conjugation of the aromatic ring with empty orbitals of the phosphorus.Such a stabilization is not available to the nitrogen compounds.
- Ikuta, S.,Kebarle, P.,Bancroft, G. Michael,Chan, Tammy,Puddephatt, Richard J.
-
p. 5899 - 5902
(2007/10/02)
-
- Synthesis and characterization of dimeric zirconium(III) complexes. Structure of "zirconocene"
-
Dimeric Zr(III) complexes have been prepared by thermolysis of (η5-C5H5)2Zr II-bis(phosphine) compounds. These dimeric Zr(III) complexes can also be prepared by treating "zirconocene" with phosphines.
- Gell, Kerrie I.,Harris, Thomas V.,Schwartz, Jeffrey
-
p. 481 - 488
(2008/10/08)
-
- PHOSPHORORGANISCHE VERBINDUNG 94. VEBER DEN EINFLUSS DES POTENTIALS AUF DIE PRODUKTZUSAMMENSETZUNG BEI DER KATHODISCHEN SPALTUNG VON DIMETHYLDIPHENYL-PHOSPHONIUMBROMID UND DIE KONSEQUENZEN FUER DEN REAKTIONSMECHANISMUS
-
Following on from an earlier investigation, we studied the influence of potential on the product ratio Ph2PMe/PhPMe2, in the cathodic reduction of dimethyl-diphenylphosphoniumbromide.A reaction mechanism is proposed by consideration of energy parameters, which is in good agreement with the preparative results.
- Hall, Elizabeth A. H.,Horner, Leopold
-
p. 231 - 234
(2007/10/02)
-
- Phosphinegold (I) salts having antiarthritic activity
-
The compounds are (pyridine) (trisubstituted phosphine) gold(I) salts which have antiarthritic activity.
- -
-
-
- Tri-substituted phosphinegold(I) 1-thio-β-D-glucopyranosides
-
The compounds are tri-substituted phosphinegold(I) 1-thio-β-D-glucopyranosides which have antiarthritic activity and, in particular, are of use in the treatment of rheumatoid arthritis. Of the three substituents on the phosphine one is optionally substituted phenyl and the others are lower alkyl or lower alkoxy.
- -
-
-
