Free PPh3 Research Articles

Определение кинетического порядка реакции на всем ее протяжении в исследовании влияния сольватационного фактора на гидрокарбометоксилирование циклогексена, катализируемое палладий-фосфиновыми системами

The purpose of the study was to investigate homogeneous catalytic reaction of cyclohexene hydrocarbomethoxylation leading to the methyl cyclohexanecarboxylate formation. Pd(PPh3)2Cl2 and Pd(OAc)2 which were promoted by free PPh3 and p-toluenesulfonic acid were used as catalytic precursors. In the temperature range 358--393 K, we studied the methanol concentration effect on the value of kinetic order of the reaction with respect to cyclohexene for the duration of the reaction. Findings of research show that the kinetic order increased from 1 to 10 with temperature increase and methanol concentration rise. We compared the kinetic order values for the duration of the reaction and the concentration order with respect to cyclohexene, which is equal to 1, set for the initial rate region. Based on this comparison, it was suggested that the formation of inactive palladium complexes is progressed by the action of excess methanol at elevated temperatures. We found that the regularities of methanol effect on the cyclohexene hydrocarbomethoxylation rate for the duration of the reaction were agreed with the regularities discovered for the initial rate region. With consideration of the data about enthalpy change in the ligand exchange reactions between the palladium complexes with participation of CH3OH, СО and PPh3, we draw the conclusion about the dominant contribution of specific solvation to the catalyst deactivation in the conditions of high methanol concentrations

Platinum phosphinothiolato hydride complexes: synthesis, structure and evaluation as tin-free hydroformylation catalysts.

Ligand 2-diphenylphosphinothiophenol (Hsarp) reacted with Pt(PPh3)4 to yield trans-[PtH(sarp)(PPh3)], which undergoes fast exchange with free PPh3 on the NMR time scale and very slowly and reversibly formed some cis-[PtH(sarp)(PPh3)] over time in solution (11%, 24 h). Reaction of trans-[PtH(sarp)(PPh3)] with Hsarp in boiling toluene gave cis- and trans-[Pt(sarp)2]; the cis isomer being more stable. These complexes were characterized by (1)H and (31)P NMR and also analyzed by XRD in the case of trans-[PtH(sarp)(PPh3)], trans-[Pt(sarp)2], and cis-[Pt(sarp)2]. trans-[PtH(sarp)(PPh3)] was evaluated as a preformed, tin-free hydroformylation catalyst on styrene and found active at 100 °C, at pressures over 75 bar, yielding phenylpropanal (regioselectivities up to 83% in 2-phenylpropanal), with total conversions to aldehydes up to 100% at styrene/platinum ratios from 400/1 to 1000/1 and minimal hydrogenation products.

Observation of Room Temperature B–Cl Activation of the HCB11Cl11– Anion and Isolation of a Stable Anionic Carboranyl Phosphazide

The perchlorinated carba-closo-dodecaborate anion is typically inert toward B-Cl functionalization. We present here the observation of two competing reactions that occur with this anion at ambient temperature. When this molecule is treated with n-BuLi and subsequently reacted with tosyl azide, a cycloaddition occurs and results in chloride substitution at a B-Cl vertex. The competing and dominant pathway is a substitution reaction to form the azide N3CB11Cl11(-). This rare anionic carboranyl azide reacts with PPh3 in FC6H5 to afford a stable anionic phosphazide. When dissolved in tetrahydrofuran, the phosphazide is in equilibrium with free PPh3 and N3CB11Cl11(-). Both the triazole and phosphazide are characterized by single-crystal X-ray diffraction, NMR and IR spectroscopy, and high-resolution mass spectrometry.

Conformational analysis of triphenylphosphine in square planar organometallic complexes: [(PPh3)(ML1L2L3)] and [M(acac)(L′)(PPh3)

The conformation analysis of free PPh(3) and PPh(3) coordinated to tetrahedral, trigonal-bipyramidal, octahedral or square planar achiral metal centres is discussed. Results from ADF calculations, in agreement with experimental structures, show that favoured degenerate conformations of complex-bound PPh(3) in square planar [(PPh(3))(ML(1)L(2)L(3))] and [M(acac)(L')(PPh(3))] complexes can be obtained by applying the following principles (P helicity, view along P-M axis), (i) superimpose C(ortho) of the vertical ring A onto the nadir plane perpendicular to the square plane and allow ring A to tilt towards the smallest ligand, (ii) allow ring B to tilt in the space below the smallest ligand in the quadrant between the nadir plane below the complex and a horizontal plane through the SQP of the complex, (iii) tilt ring C over the largest ligand and (iv) allow correlated tilting of rings A, B and C to minimize inter ring-ring and inter ring-ligand interactions.

The role of the atomic charges on the ligands and platinum(ii) in affecting the cis and trans influences in [PtXL(PPh3)2]+ complexes (X = NO3, Cl, Br, I; L = 4-substituted pyridines, amines, PPh3). A 31P NMR and DFT investigation

One bond Pt-P coupling constants (1)J(PtP) of a series of cationic complexes [PtXL(PPh(3))(2)](+) (X = NO(3), Cl, Br, I; L = 4-Z-pyridines, Z = electron withdrawing or releasing groups, 4a-k; or X = Cl, L = NH(3), PhCH(2)NH(2) and (i)PrNH(2), 5a-c) have been used to establish the trans and cis influence sequences of X and pyridines. The crystal structure of compound 4f(BF(4)) with Z = (t)Bu has been resolved. In the pyridine complexes 4a-d (Z = H, variable X), both the trans and cis influence series of the anionic ligands X decrease along the same sequence I > Br > Cl > NO(3), as previously found for [PtX(PPh(3))(3)](+) (X = NO(3), Cl, Br, I, 3a-d), however in 4a-d the cis influence turns out to be more important than the trans. On the contrary, in [PtCl(4-Z-py)(PPh(3))(2)](+) (4b,e-k) the sequence of the trans influence of the 4-Z-pyridines is opposite to that of the cis, the latter being Z = CN > CHO > Br > PhCO > H > Me > (t)Bu > NH(2), i.e. the most basic pyridine gives rise to the lowest cis influence. This correlation was found to hold also for complexes 5a-c (L = amines). All the observed trends have been fully reproduced by B3LYP/def2-SVP DFT calculations, by looking at the relevant optimized bond lengths of selected complexes of type 3, 4 and 5. Subsequent evaluation of the atomic charges, by resorting to two independent methods, i.e., the Natural Bond Order analysis of the wavefunction and the Bader's Quantum Theory of Atoms in Molecules, allowed for rationalization of the origin of the cis and trans influences. The negative charge on the nitrogen atoms of free pyridines becomes more negative upon protonation and even more so when coordinated to the [PtCl(PPh(3))(2)](+) moiety. The least negatively charged nitrogen atom of coordinated pyridines is that of 4-CN-py (the highest cis influencing pyridine derivative), which gives rise to the lowest positive charge on Pt, confirming the relationship between the lowering of the charge on the metal ion and a high cis influence. The trans influence can be described in terms of competition between the charges on the two trans donor atoms. In contrast with the behaviour of pyridines, the positive charge on the phosphorous atom of free PPh(3) increases upon coordination to Pt(II), moreover the PPh(3) ligands acquire a substantial positive charge, thus efficiently delocalising the charge of the cationic complex.

Amino-functionalized SBA-15 immobilized NiBr 2(PPh 3) 2 as a highly effective catalyst for ATRP of MMA

3-Aminopropyltriethoxysilane modified mesoporous SBA-15 was used to load the NiBr 2(PPh 3) 2 as a heterogeneous catalyst for the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) when initiated by ethyl 2-bromoisobutyrate (EBr iB) in toluene. Due to the Lewis acid sites formed by the surface silanol groups of the mesoporous material, some monomer conversions were much higher even than that catalyzed by the homogeneous catalyst NiBr 2(PPh 3) 2 under the same reaction conditions while polydispersity indices (PDI) of the products still kept narrow (1.20–1.30). At the same time, the activity of the catalyst could be modulated by changing the quantity of the –NH 2, SBA-15 and the free PPh 3. In the recycling experiments, the recovered heterogeneous catalyst basically maintained its catalytic activity without any addition of new heterogeneous catalyst.

Fluxionality of [(Ph3P)3M(X)] (M = Rh, Ir). The Red and Orange Forms of [(Ph3P)3Ir(Cl)]. Which Phosphine Dissociates Faster from Wilkinson’s Catalyst?

NMR studies of intramolecular exchange in [(Ph(3)P)(3)Rh(X)] (X = CF(3), CH(3), H, Ph, Cl) have produced full sets of activation parameters for X = CH(3) (E(a) = 16.4 +/- 0.6 kcal mol(-1), DeltaH(double dagger) = 16.0 +/- 0.6 kcal mol(-1), and DeltaS(double dagger) = 12.7 +/- 2.5 eu), H (E(a) = 10.7 +/- 0.2 kcal mol(-1), DeltaH(double dagger) = 10.3 +/- 0.2 kcal mol(-1), and DeltaS(double dagger) = -7.2 +/- 0.8 eu), and Cl (E(a) = 16.3 +/- 0.2 kcal mol(-1), DeltaH(double dagger) = 15.7 +/- 0.2 kcal mol(-1), and DeltaS(double dagger) = -0.8 +/- 0.8 eu). Computational studies have shown that for strong trans influence ligands (X = H, Me, Ph, CF(3)), the rearrangement occurs via a near-trigonal transition state that is made more accessible by bulkier ligands and strongly donating X. The exceedingly fast exchange in novel [(Ph(3)P)(3)Rh(CF(3))] (12.1 s(-1) at -100 degrees C) is due to strong electron donation from the CF(3) ligand to Rh, as demonstrated by computed charge distributions. For weaker donors X, this transition state is insufficiently stabilized, and hence intramolecular exchange in [(Ph(3)P)(3)Rh(Cl)] proceeds via a different, spin-crossover mechanism involving triplet, distorted-tetrahedral [(Ph(3)P)(3)Rh(Cl)] as an intermediate. Simultaneous intermolecular exchange of [(Ph(3)P)(3)Rh(Cl)] with free PPh(3) (THF) via a dissociative mechanism occurs exclusively from the sites cis to Cl (E(a) = 19.0 +/- 0.3 kcal mol(-1), DeltaH(double dagger) = 18.5 +/- 0.3 kcal mol(-1), and DeltaS(double dagger) = 4.4 +/- 0.9 eu). Similar exchange processes are much slower for [(Ph(3)P)(3)Ir(Cl)] which has been found to exist in orange and red crystallographic forms isostructural with those of [(Ph(3)P)(3)Rh(Cl)].

Synthesis, X-ray structure and electrochemical oxidation of palladium(ii) complexes of ferrocenyldiphenylphosphine

Four new complexes, [PdX(κ(2)-2-C(6)R(4)PPh(2))(PPh(2)Fc)] [X = Br, R = H (1), R = F (2); X = I, R = H (3), R = F (4)], containing ferrocenyldiphenylphosphine (PPh(2)Fc) have been prepared and fully characterised. The X-ray structures of complexes trans-1, cis-2 and cis-4, and that of a decomposition product of 4, [Pd(κ(2)-2-C(6)F(4)PPh(2))(μ-I)(μ-2-C(6)F(4)PPh(2))PdI(PPh(2)Fc)] (5), have been determined. These complexes show a distorted square planar geometry about the metal atom, the bite angles of the chelate ligands being about 69°, as expected. The cis/trans ratio of 1-4 in solution is strongly dependent on solvent. The new complexes and the uncoordinated PPh(2)Fc ligand were electrochemically characterised by cyclic and rotating disk voltammetry, UV-visible spectroelectrochemistry, and bulk electrolysis in dichloromethane and acetonitrile. In both cases, oxidation occurs at both the ferrocene and phosphine centres, but the complexes oxidise at more positive potentials than uncoordinated PPh(2)Fc; subsequently, the metal-phosphorus bond is cleaved, leading to free PPh(2)Fc(+), which undergoes further chemical and electrochemical reactions.

Photophysical properties of copper(I) and zinc(II) complexes containing phosphinoquinoline ligands

Several copper(I) and zinc(II) complexes with 8-(diphenylphosphino)quinoline (PPh 2qn) or 8-diphenylphosphinoquinaldine (PPh 2qna) have been prepared. These ligands contain both imine and phosphine moieties, which can act as coordinating groups. X-ray analysis of the Cu(I) complexes reveals that [Cu(PPh 2qn) 2]PF 6 ( Cu-1) and [Cu(PPh 2qn) 2]PF 6 ( Cu-2), coordinated by two PPh 2qn and PPh 2qna ligands respectively, are obtained. In the Zn(II) complexes, a structural study shows that [ZnCl 2(PPh 2qn)] ( Zn-1), [ZnBr 2(PPh 2qn)] ( Zn-2) and [ZnI 2(PPh 2qn)] ( Zn-3) are coordinated by one PPh 2qn ligand and two of the corresponding halogeno ligands (Cl −, Br − and I −). In the solid state Cu-1 and Cu-2 show luminescence which is assigned to a 3MLCT transition involving π∗ of the quinoline group, as shown in the [Cu(dmp)(diphosphine)] + complexes; due to the reduced bulkiness of the coordination sphere around the copper atom, no emission is observed in solution. Zn-1 shows a similar emission band to that of free PPh 2qn at both room temperature and 77 K. It suggests the emission bands should be assigned to a ligand-centered (LC) transition. In the solid state, it is found that the emissive energy of the complexes shift to lower energy and the energy depends on the halogeno ligands in the zinc complexes.

Nickel(II) Complexes of Bidentate N‐Heterocyclic Carbene/Phosphine Ligands: Efficient Catalysts for Suzuki Coupling of Aryl Chlorides.

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Nickel(II) Complexes of Bidentate N‐Heterocyclic Carbene/Phosphine Ligands: Efficient Catalysts for Suzuki Coupling of Aryl Chlorides

Nickel(II) complexes of bidentate N-heterocyclic carbene (NHC)/phosphane ligand L were prepared and structurally characterized. Unlike palladium, which forms [PdCl(2)(L)], the stable nickel product isolated is the ionic [Ni(L)(2)]Cl(2). These Ni(II) complexes are highly robust in air. Among different N-substituents on the ligand framework, the nickel complex of ligand L bearing N-1-naphthylmethyl groups (2 a) is a highly effective catalyst for Suzuki cross-coupling between phenylboronic acid and a range of aryl halides, including unreactive aryl chlorides. The activities of 2 a are largely superior to those of other reported nickel NHC complexes and their palladium counterparts. Unlike the previously reported [NiCl(2)(dppe)] (dppe=1,2-bis(diphenylphosphino)ethane), 2 a can effectively catalyze the cross-coupling reaction without the need for a catalytic amount of PPh(3), and this suggests that the PPh(2) functionality of hybrid NHC ligand L can partially take on the role of free PPh(3). However, for unreactive aryl chlorides at low catalyst loading, the presence of PPh(3) accelerates the reaction.

Synthesis of Ni(ii), Pd(ii) and Pt(ii) complexes containing chiral phosphino-thiol and -thioether ligands

The chiral P,S ligand 1-(diphenylphosphino)butane-2-thiol, L1H, and its thioether methyl derivative L1Me have been synthesized. L1H reacts with divalent Ni, Pd and Pt salts to form phosphinothiolato complexes of general formula [M(L1)Cl]2 (1, M = Ni), (2, M = Pd), M(L1)2 (3, M = Ni), (4, M = Pd), (5, M = Pt) and M(L1)(PR3)X, (6, M = Pd, R = Ph, X = Cl), (7, M = Pd, R = nBu, X = Cl), (8, M = Pt, R = Ph, X = H). Single crystal X-ray crystallography reveals a ‘butterfly’ shape for the dimeric structures of nickel and palladium complexes, 1 and 2 respectively. The P,S chelate ring, according to solid state structural data and NMR analysis, adopts a preferred δ skew-conformation for the S isomer and a λ conformation for the R isomer. Complex 6 dissociates in chloroform solutions to form the dimeric species 2 and free PPh3. Thermodynamic parameters for this process have been calculated.

Synthesis, electrochemical behavior and X-ray crystal and molecular structures of [Fe(diene)(CO) 2PPh 3] (diene=chalcone, sorbic acid)

The compounds [Fe(ch)(CO) 2PPh 3] ( 1) (ch=chalcone) and [Fe(sba)(CO) 2PPh 3] ( 2) (sba=sorbic acid) were prepared by irradiating the tetracarbonyltriphenylphosphineiron(0) complex in benzene in the presence of ch or sba. The compounds were characterized by infrared and 31P NMR spectroscopies. Their electrochemical behavior was investigated by cyclic voltammetry and the results suggest that their oxidations occur by more than one electrochemical step, producing free ch and sba, free PPh 3 and solvated Fe(III). It was observed that sba ligand contributes more effectively to the stabilization of metal center in these complexes. The X-ray crystal and molecular structures of 1 and 2 were determined; it was shown that the Fe atom adopts a distorted octahedral coordinated geometry in which three of the sites are occupied by the ch or sba ligand. The [Fe(ch)(CO) 2PPh 3] complex is a monomer and the unit cell of complex 2 contains exist two identical and crystallographically independent molecules of [Fe(sba)(CO) 2PPh 3] which are linked by short hydrogen bonds OH· · ·O

1-Heptene hydroformylation over phosphinated silica-anchored rhodium thiolate complexes

The rhodium (I) pentaflurophenylthiolate complexes [Rh(μ-SC 6F 5)(COD)] 2 and [Rh(μ-SC 6F 5)(CO) 2] 2 were anchored on phosphinated silica. These catalysts were tested in the hydroformylation reaction of 1-heptene in toluene at 343–393 K using a gas feed ratio of CO:H 2=1 mole. The conversion of 1-heptene versus the reaction time followed S-shaped curves in which the induction period depended on the catalyst precursor and number of cycles in the reaction. Selectivity towards linear aldehyde was high, although the extent of isomerisation to internal olefins was found to be important. The addition of free PPh 3 to the reaction medium markedly increased the yield to linear aldehyde but the rate of the reaction appeared to be retarded. The results are compared with those obtained on using these complexes in homogeneous phase under similar conditions. The effects of temperature, pressure and the phosphine/Rh mole ratio on the reaction rate and selectivity are discussed.

Thioether- and selenoether-carboxylates in palladium chemistry: conclusive proof of hemilabile properties of O–Se ligands

Reaction of trans-[PdCl(Ph)(PPh 3) 2] with the thallium salts R–X–(CH 2) n –COOTl ( n=1, X=S, R=Me, Et, i-Pr, t-Bu, Ph; n=1, X=Se, R=Me, Ph; n=2, X=S, R=Et, Ph) yields the compounds trans-[Pd(OOC–(CH 2) n –X–R–κ 1- O)Ph(PPh 3) 2] ( 1a– 1i). In solution, complexes 1a– 1i participate in hemilabile equilibria in which one PPh 3 ligand is replaced by a sulphur/selenium atom of the ligand to afford the O–S/Se chelates under certain circumstances. Solid state structures of the monodentate complex 1h as well as its corresponding chelate ( 2h) together with the NMR observation of both species in solution, conclusively prove the hemilabile properties of this O–Se ligand. Depending on the size of the substituent on the potential sulphur or selenium donor atom, however, a PPh 3 ligand is not always displaced upon donor atom coordination. In such equilibria no free PPh 3 is detected and a five-coordinate square pyramidal structure is proposed for the O–S/Se chelate. The position of the relevant equilibrium depends on both the basicity of the potential sulphur or selenium donor atom as well as on the polarity of the solvent.

Synthesis and molecular structure of [RuCl{C(CHPh)OC(O)CH 2CH 3}(CO)(PPh 3) 2]: a real intermediate in ruthenium complex-catalyzed selective synthesis of a ( Z)-enol ester

Reaction of [RuCl(η 2-O 2CCH 2CH 3)(CO)(PPh 3) 2] ( 1) and phenylacetylene gives [RuCl{C(CHPh)OC(O)CH 2CH 3}(CO)(PPh 3) 2] ( 2a). The X-ray structure analysis of 2a reveals that it includes a ( Z)-enol ester-like 1-propanoyloxy-2-phenylethenyl- C 1, O ligand. In the catalytic addition of propanoic acid to phenylacetylene, the complex 2a acts as a real intermediate that gives ( Z)-2-phenylethenyl propanoate, selectively. The presence of the free PPh 3 in the reaction mixture depresses formation of some dicarbonylruthenium species that catalytically produce ( E)- and Markovnikov-type enol esters.

Surface active rhodium catalysts for hydroformylation of higher alkenes in two-phase systems

A variety of water-soluble phosphine and phosphite ligands with phase-transfer ability based on functionalized polyethylene oxide has been synthesized. The corresponding rhodium complexes show high catalytic activity in aqueous biphasic hydroformylation of higher alkenes under mild conditions. The catalysts can be easily separated from products and reused. The effect of ligands structure, temperature, ligand-to-rhodium ratio, addition of free PPh 3 and P(OPh) 3 on catalytic stability and activity is studied.

Reactions of the Eight-Coordinate Rhenium Complex ReH4(hq)(PPh3)2 (hq = 2-Hydroxyquinoline Monoanion) with Monodentate Tertiary Phosphines: Formation of Pentagonal Bipyramidal Dihydridorhenium(III) Complexes of the Type ReH2(hq)(PPh3)2(PR3)

The reactions of ReH4(hq)(PPh3)2, where hq represents the monoanion of 2-hydroxyquinoline, with monodentate phosphines afford the seven-coordinate complexes ReH2(hq)(PPh3)2(PR3) (PR3 = PMe3 (1), PMe2Ph (2), PMePh2 (3), PPh3 (4), and PHPh2 (5)) which have been shown to possess pentagonal bipyramidal structures on the basis of X-ray crystal structure determinations of 1, 4, and 5. The unique PR3 ligand occupies the pentagonal plane in the case of 1 and 5. The reactions of 4 with PMe3 and PHPh2 lead to substitution of one of the PPh3 ligands and the formation of 1 and 5, respectively. The mild thermolysis of solutions of 4 in refluxing benzene affords the diphenyphosphine complex 5, along with some decomposition of 4 and the release of free PPh3; when this reaction is carried out in C6D6, the released PPh3 is found to contain the isotopomers PPh3-d0 through PPh3-d6 with the deuteration taking place only in the ortho positions.

Synthesis and Structure of Pd4(μ-PtBu2)2(μ-CS2)(PPh3)2I2, a Neutral Palladium(I) Derivative with a Hexacoordinate Carbon and a CS2 Molecule Bridging Four Palladium Centers

The dinuclear CS2 complex [Pd2(μ-PtBu2)(μ,η2:η2-CS2)(PPh3)2]BF4, (2)BF4, reacts with Me4NI to yield the neutral tetranuclear Pd(I) derivative Pd4(μ-PtBu2)2(μ4-CS2)(PPh3)2I2 (4), which has been characterized by single-crystal X-ray diffraction. Its unusual molecular structure with a formally hexacoordinate carbon atom, as well as that of (2)+ with a planar tetracoordinate carbon can be explained on the basis of fragment MO considerations and EHMO model calculations. The reaction proceeds stepwise, with the relatively fast substitution of CS2 by the iodide ion giving the intermediate complex Pd2(μ-PtBu2)(μ-I)(PPh3)2 (3). The latter further reacts slowly with free CS2 to give complex 4 and free PPh3. Complex 3 was also prepared and isolated pure by reacting [Pd2(μ-PtBu2)(PPh3)3]BF4 with Me4NI.

Cyclometallation of 2-phenylaniline and ( R)- α-methylbenzylamine by palladium(II) acetate. X-ray molecular structure of [P [formula omitted]H 2C 6H 4)C 6H 4}Br(PPh 3)

The action of palladium(II) acetate on the primary amines 2-phenylaniline and ( R)- α-methylbenzylamine and subsequent treatment with LiBr allows the preparation of the corresponding cyclopalladated dimers [P d(CN )Br] 2 ( 1a and 1b respectively). Mononuclear compounds [P d(CN )Br(L)], 3 ( L = py−d 5) and 2 ( L = PPh 3) , have ben obtained by reaction of 1 with py- d 5 and PPh 3. Addition of PPh 3 to chloroform solutions of 2 produces a rapid exchange between coordinated and free PPh 3. 31P{ 1H} NMR at variable temperature suggests that this exchange proceeds for 2a through the fast equilibrium [Pd(CN)Br(PPh 3) 2]⇔[P (CN )Br(PPh 3)], while the usual mechanism in substitution reactions in d 8 planar square complexes is involved in the case of 2b. The X-ray crystal structure of 2a has been determined. 2a crystallizes in the triclinic space group P 1 with a = 12.182(3), b = 10.502(2), c = 9.998(2) A ̊ , α = 99.24(2), β = 94.69(2) and γ = 99.13(2)° .