Polarography, cyclic voltammetry and coulometry reveal that a catalytic reduction of the tetraalkylammonium cation, R4N+, of the supporting electrolyte is involved in the electrochemical reduction of triphenylphosphine (TPP) and its oxide (TPPO) in aprotic solvents such as acetonitrile, dimethylformamide and hexamethylphosphoramide. There is however progressive consumption of TPP and TPPO resulting in the final formation of phenyl substitution products (RPØ2 and ROPØ2). Comparison with the reduction of the BuPØ3+ cation allows to propose the following mechanism which involves a chemical type catalytic process:
Redox type catalytic mechanisms are discussed and shown to be unlikely. Values of the alkylation rate constant are derived from the polarographic or the coulometric data or from cyclic voltammetry according to its magnitude which varies with the solvent. TPP anion radical appears as more readily alkylable than TPPO anion radical. 相似文献
The cobalt(II) porphyrin complex (CoTPP) was found to be an efficient catalyst for the Wittig type olefination of acyl phosphonates with ethyl diazoacetate (EDA) in the presence of triphenylphosphine (Ph3P). By using this one pot methodology under mild conditions, densely functionalized vinyl phosphonates were obtained in high yields and high E/Z selectivities in relatively short reaction times. A rather broad substrate spectrum and steric influence on the reaction rate were observed. 相似文献
The interconversion between difluoromethylene ylide and difluorocarbene is described. The difluoromethylene ylide precursor, Ph3P+CF2CO2?, could be turned into an efficient difluorocarbene reagent, whereas the classical difluorocarbene reagents, HCF2Cl and FSO2CF2CO2TMS, could generate highly reactive difluoromethylene ylide. Thus the Wittig difluoro‐olefination and difluorocyclopropanation could be selectively realized by using the same reagent. In addition, the ylides obtained from different carbene sources showed different reactivity in Wittig reactions. 相似文献
Recently, Brønsted 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. 相似文献
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. 相似文献
The syntheses of salts containing ligand‐stabilized Ph3Sb2+ and Ph3Bi2+ dications have been realized by in situ formation of Ph3Pn(OTf)2 (Pn=Sb or Bi) and subsequent reaction with OPPh3, dmap and bipy. The solid‐state structures demonstrate diversity imposed by the steric demands and nature of the ligands. The synthetic method has the potential for broad application enabling widespread development of the coordination chemistry for PnV acceptors. 相似文献
A series of nine different known ionic liquids or low melting salts was synthesised and purified. They are composed of the [NTf2]– (bis(trifluoromethane)sulfonimide), [OTf]– (trifluoro-methane-sulfonate), or [B(CN)4]– (tetracyanidoborate) anion and [Ph4P]+ (tetraphenylphosphonium), [Ph3BzP]+ (triphenylbenzyl phosphonium), [nBu4P]+ (tetra-nbutylphosphonium), [nBuPh3P]+ (tri-phenyl-nbutylphosphonium), [nBu4N]+ (tetra-nbutylammonium), or the [PPN]+ (bis(triphenylphosphine)iminium) cation. Precise vapour pressure data and enthalpies of vaporisation were measured using the Quartz Crystal Microbalance (QCM) method and evaluated. Structure-property relations are established using the obtained data as well as literature known data of ILs with alkyl-substituted imidazolium cations. It turns out that ILs with the tetracyanidoborate anion have even higher values of the enthalpy of vaporisation than those with the common [NTf2]− or [OTf]− anion and therefore are even less volatile. 相似文献
[LCRP((PhP)2C2H4)][OTf] ( 4 a,b [OTf]) and [LCiPrP(PPh2)2][OTf] ( 5 b [OTf]) were prepared from the reaction of imidazoliumyl-substituted dipyrazolylphosphane triflate salts [LCRP(pyr)2][OTf] ( 3 a,b [OTf]; a : R=Me, b =iPr; LCR=1,3-dialkyl-4,5-dimethylimidazol-2-yl; pyr=3,5-dimethylpyrazol-1-yl) with the secondary phosphanes PhP(H)C2H4P(H)Ph) and Ph2PH. A stepwise double P−N/P−P bond metathesis to catena-tetraphosphane-2,3-diium triflate salt [(Ph2P)2(LCMeP)2][OTf]2 ( 7 a [OTf]2) is observed when reacting 3 a [OTf] with diphosphane P2Ph4. The coordination ability of 5 b [OTf] was probed with selected coinage metal salts [Cu(CH3CN)4]OTf, AgOTf and AuCl(tht) (tht=tetrahydrothiophene). For AuCl(tht), the helical complex [{(Ph2PPLCiPr)Au}4][OTf]4 ( 9 [OTf]4) was unexpectedly formed as a result of a chloride-induced P−P bond cleavage. The weakly coordinating triflate anion enables the formation of the expected copper(I) and silver(I) complexes [( 5 b )M(CH3CN)3][OTf]2 (M=Cu, Ag) ( 10 [OTf]2, 11 [OTf]2). 相似文献
2,2-Dimethyl-5-(triphenylphosphoranylidene)acetyl-1,3-dioxan-4,6-dione (3) is a new activated β-ketoacyl equivalent, readily prepared in quantitative yield by reaction of Meldrum’s acid with the stable ylide Ph3PCCO. Its reaction with α-amino esters affords the corresponding N-(β-ketoacyl)amino ester ylides which, when treated with aldehydes and KOtBu, undergo a simultaneous Wittig olefination cum Dieckmann cyclisation to yield the respective 3-enoyltetramic acids. 相似文献
The lithium diphenylphosphonium di(methylide) Ph2 P(CH2)2 Li 1 readily attacks cyclic carbonates, carbamates, and thiocarbamates, resulting in “pseudo-acylation” products, after a ring-opening step. Thus, new stabilized ylides are prepared, which can be used in situ as carbonyl olefination reagents towards aldehydes. This procedure is a new one-pot method for the synthesis of (E)-vinylic esters and amides, bearing a free ω-hydroxyl group. When a thiocarbamate is the initial substrate for 1 , a Michael-type cyclization occurs, following the Wittig olefination, resulting in the one-pot preparation of 7-membered heterocycles. 相似文献
[LCRP((PhP)2C2H4)][OTf] ( 4 a,b [OTf]) and [LCiPrP(PPh2)2][OTf] ( 5 b [OTf]) were prepared from the reaction of imidazoliumyl‐substituted dipyrazolylphosphane triflate salts [LCRP(pyr)2][OTf] ( 3 a,b [OTf]; a : R=Me, b =iPr; LCR=1,3‐dialkyl‐4,5‐dimethylimidazol‐2‐yl; pyr=3,5‐dimethylpyrazol‐1‐yl) with the secondary phosphanes PhP(H)C2H4P(H)Ph) and Ph2PH. A stepwise double P?N/P?P bond metathesis to catena‐tetraphosphane‐2,3‐diium triflate salt [(Ph2P)2(LCMeP)2][OTf]2 ( 7 a [OTf]2) is observed when reacting 3 a [OTf] with diphosphane P2Ph4. The coordination ability of 5 b [OTf] was probed with selected coinage metal salts [Cu(CH3CN)4]OTf, AgOTf and AuCl(tht) (tht=tetrahydrothiophene). For AuCl(tht), the helical complex [{(Ph2PPLCiPr)Au}4][OTf]4 ( 9 [OTf]4) was unexpectedly formed as a result of a chloride‐induced P?P bond cleavage. The weakly coordinating triflate anion enables the formation of the expected copper(I) and silver(I) complexes [( 5 b )M(CH3CN)3][OTf]2 (M=Cu, Ag) ( 10 [OTf]2, 11 [OTf]2). 相似文献
The coordination chemistry of the stiboranes Ph4Sb(OTf) ( 1 a , OTf = OSO2CF3) and Ph3Sb(OTf)2 ( 3 ) with Lewis bases has been investigated. The significant steric encumbrance of the Sb center in 1 a precludes interaction with most ligands, but the relatively low steric demands of 4‐methylpyridine‐N‐oxide (OPyrMe) and OPMe3 enabled the characterization of [Ph4Sb(OPyrMe)][OTf] ( 2 a ) and [Ph4Sb(OPMe3)][OTf] ( 2 b ), rare examples of structurally characterized complexes of stibonium acceptors. In contrast, 3 was found to engage a variety of Lewis bases, forming stable isolable complexes of the form [Ph3Sb(donor)2][OTf]2 [donor=OPMe3 ( 6 a ), OPCy3 ( 6 b , Cy=cyclohexyl), OPPh3 ( 6 c ), OPyrMe ( 6 d )], [Ph3Sb(dmap)2(OTf)][OTf] ( 6 e , dmap=4‐(dimethylamino)pyridine) and [Ph3Sb(donor)(OTf)][OTf] [donor=1,10‐phenanthroline ( 7 a ) or 2,2′‐bipy ( 7 b , bipy=bipyridine)]. These compounds exhibit significant structural diversity in the solid‐state, and undergo ligand exchange reactions in line with their assignment as coordination complexes. Compound 3 did not form stable complexes with phosphine donors, with reactions instead leading to redox processes yielding SbPh3 and products of phosphine oxidation. 相似文献
Abstract Atmospheric pressure chemical ionization mass spectrometry (APCI–MS) has been utilized in the characterization of two series of platinum dithiolene complexes, (COD)Pt(dt) 1, (COD)–Pt(edt) 2, (COD)Pt(dmid) 3, (COD)Pt(mnt) 4, (COD)Pt(eddo) 5, (COD)Pt(dddt) 6 and (Ph3P)2Pt(dt) 7, (Ph3P)2Pt(edt) 8, (Ph3P)2Pt(dmid) 9, (Ph3P)2Pt(dmit) 10, (Ph3P)2Pt(mnt) 11 (where COD = 1,5–cyclooctadiene, dt = ethane–1,2–dithiolate, edt = ethylene–1,2–dithiolate, dmid = 1,3–dithiole–2–oxo–4,5–dithiolate, dmit = 1,3–dithiole–2–thione–4,5–dithiolate, mnt = maleonitrile–1,2–dithiolate, eddo = 4–(ethylene–1′,2′–dithiolate)–1,3-dithiole–2–one, and dddt = 5,6–dihydro–1,4–dithiin–2,3–dithiolate). The series that contains triphenylphosphine is labile toward the loss of HPPh3+. In addition, an orthometallated species involving the platinum and triphenylphosphine is identified. A dimer is identified for 2, which is shown to be a product of the experiment and not present in the parent material. In addition, a 1:1 adduct with NH4+ is identified for 4 and 11 where the NH4+ originates from the acid hydrolysis of acetonitrile. Finally, a highly unique ion, Pt+, a bare platinum ion, is observed in all COD complexes indicating that a radical mechanism must accompany the decomposition of the COD complexes during the fragmentation process. 相似文献
The enolate ylide Ph3P+C?C(Ph)O?Li+ obtained by the reaction of HMPT-Li with the benzoylmethylenetriphenylphosphorane Ph3PCHCOPh reacts with aliphatic ketones, in contrast to its precursor. This condensation makes it possible to prepare β,γ-unsaturated ketones, of type RCHC(R′)CH2COPh, instead of the α,β isomer usually obtained in a Wittig reaction. 相似文献
Phosphonium ylides Ph3PCHR (R = H, CH3, C2H5, n-C3H7, n-C5H11) react readily with perhalofluoroalkanes to afford regiospecifically α-haloalkylphosphonium salts Ph3P+-CHXR Y− (X = I, Br, Cl) in good yields. These reactions reveal a new type of reactivity of phosphonium ylides, i.e., the halophilic attack on CX bonds, and may be useful for the regiospecific synthesis of substituted haloolefins via Wittig reaction. 相似文献
Tris(triphenylphosphine)methylcobalt;(Ph3P)3CoCH3, reacts with diphenyl-acetylene to give α-methylstilbene as the sole addition product.(Ph3P)3CoCH3 can be used as an alkylation reagent in ethers or in aromatic solvents. 相似文献
The crystal structure of the [Tb(BTFA)2(NO3)(TPPO)2] complex (TPPO is triphenylphosphine oxide, BTFA is benzoyltrifluoracetone), which exhibits strong triboluminescence, has been established by X-ray crystallography. The crystals are triclinic: a = 11.668(3) Å, b = 11.700(3) Å, c = 12.512(3) Å, α = 65.161(4°), β = 79.120(4)°, γ = 61.860(4)°, space group P1, Z = 1. The central terbium(III) atom coordinates two oxygen atoms from two triphenylphosphine oxide molecules (Tb-O, 2.264(3) and 2.273(3) Å), two oxygen atoms from the nitrate group (Tb-O, 2.460(3) and 2.476(3) Å), and four oxygen atoms from two benzoyltrifluoroacetonate groups (Tb-O, 2.329(3), 2.399(3), 2.351(3), and 2.367(3) Å). The coordination polyhedron of the Tb(III) atom is a distorted dodecahedron. The photoluminescence and triboluminescence spectra of the [Tb(BTFA)2(NO3)(TPPO)2] complex are identical and caused by the f-f luminescence of Tb3+. 相似文献
Using XRD method, we determined the atomic structure of crystals of the compound [Eu(TFA)3·2TPPO (H2O)]2, where TFA is a trifluoroacetate anion, TPPO is a triphenylphosphine oxide. The coordination polyhedra of two independent europium atoms with coordination number CN = 8 are isotypic and consist of a antiprism of [EuO8] composition. The geometric and electronic structural features of the compound corresponding to the characteristics of its luminescent properties are discussed. 相似文献