Diphenylphosphine Groups Research Articles

XPS Study of the Preparation of Single-Site Catalysts Based on Ir(I) and Rh(I) Complexes Immobilized on a SiO<sub>2</sub> Surface Using a P-Containing Linker

Samples of model single-site iridium and rhodium catalysts were synthesized by immobilization of complexes [Ir(COD)(IMes)Cl] and [Rh(COD)(IMes)Cl], where COD is cyclooctadiene-1,5 and IMes is 1,3‑bis(2,4,6-trimethylphenyl)imidazol-2-ylidene, on the surface of silicon dioxide modified with a linker containing diphenylphosphine group (Ph2P). Silicon plates with a flat surface covered with a layer of natural oxide 1–3 nm thick, Si-SiO2(nat), or with a specially grown SiO2 film (∼300 nm), Si-SiO2(ox), were used as supports. The chemical compositions of the surface of the modified silicon plates and samples of model catalysts were characterized by XPS. Based on these XPS studies, a tentative conclusion was made about the coordination of immobilized complexes to the SiO2 surface. Catalyst samples were tested in the gas-phase hydrogenation of propene with parahydrogen.

Modular synthesis of unsymmetric 1,3-diphosphinopropanes through sequential substitution reactions

Methods to synthesize diphosphines with different substituents on the two phosphorus centers are limited, particularly for the synthesis of unsymmetric bis(dialkylphosphine) ligands. Herein is reported a modular and high-yielding synthesis of borane-protected unsymmetric 1,3-bis(diphosphino)propanes containing either two dialkylphosphine moieties or one dialkylphosphine and one diphenylphosphine group. The method relies on sequential phosphine substitution on 1,3-dibromopropane. The borane-protected diphosphines are readily converted to bis(phosphonium salts), which serve as convenient preligands. Palladium(II) complexes of di-tert-butyl(3-(dicyclohexylphosphino)propyl)phosphine (tBuCyPP), di-tert-butyl(3-(diisobutylphosphino)propyl)phosphine (tBuiBuPP), and diisobutyl((3-(dicyclohexylphosphino)propyl)phosphine (CyiBuPP) have been prepared. The tBuiBuPP and CyiBuPP complexes have been structurally characterized and their structural properties compared to symmetric (1,3-diphosphinopropane)palladium dichloride structures.

Phosphine-functionalized amidinate ligated rare-earth metal complexes for highly 3,4-selective living polymerization of 1,3-conjugated dienes.

A series of rare-earth metal bis(alkyl) complexes have been prepared via protonolysis reactions of tris(aminobenzyl) complexes (Ln(CH2C6H4N(Me)2-o)3) with phosphine-functionalized amidinated ligands (DippNCN(CH2)nPPh2, n = 2 (L1-H) and n = 3 (L2-H)). The X-ray diffraction of P2-Sc (DippNCN(CH2)3PPh2Sc(CH2C6H4N(Me)2-o)2) showed the un-coordination of the diphenylphosphine group due to the inherent saturation of the central metal ion. In conjunction with [Ph3C][B(C6F5)4], all the rare-earth metal complexes showed a high catalytic activity for the polymerization of 1,3-conjugated dienes (isoprene, β-myrcene and β-farnesene), affording highly 3,4-regular polymers (up to 100% 3,4-) with high molecular weight and narrow molecular weight distribution. After the abstraction of the alkyl moiety -CH2C6H4N(Me)2-o of P1-Sc by [Ph3C][B(C6F5)4], the species with the coordination of the diphenylphosphine group to the central metal probably formed, as shown in the 31P NMR spectra and DFT calculation results, and it might serve as the true active species in the 3,4-selective polymerization of 1,3-conjugated dienes.

Investigating stimuli-responsive luminescence and aggregation-induced emission properties of o-carborane-based luminophores modified with phenanthrene or anthracene

Incorporation of a diphenylphosphine group and an o-carborane unit into luminophores leads to polymorphs and stimuli-responsive luminescence behavior.

Iminosugar-Phosphines as Organocatalysts in the [3 + 2] Cycloaddition of Allenoates and N-Tosylimines

Iminosugar derivatives containing a pyrrolidine-phosphine moiety were prepared from carbohydrates and used as catalysts in the [3 + 2] cycloaddition reaction between alkyl allenoates and electron-deficient imines. The corresponding 1,2,3,5-tetrasubstituted pyrrolines were obtained in good yields and diastereoselectivities but with moderate enantiocontrol. The stereochemical outcome of the reaction depends on the substituent at the nitrogen atom and hydroxyl groups, the configuration of the stereogenic centers and the distance between the diphenylphosphine group and the pyrrolidine skeleton of the catalyst. The preparation of both enantiomers of the catalyst allowed the corresponding enantiomeric pyrrolines to be obtained with similar yields, diastereo- and enantioselectivities.

Synthesis and crystallographic studies of 2-(di-phenyl-phosphino-thio-yl)-2-(3-oxobut-1-en-yl)ferrocene.

As a follow-up to our research on the chemistry of disubstituted ferrocene derivatives, the synthesis and the structure of the title compound, 2-(di-phenyl-phosphino-thio-yl)-2-(3-oxobut-1-en-yl)ferrocene, [Fe(C5H5)(C21H18OPS)], are described. The mol-ecule is built up from a ferrocene unit disubstituted by an S-protected di-phenyl-phosphine group and by a methyl-vinyl-ketone chain. The crystal structure features weak C-H⋯O and C-H⋯S inter-actions, which build a two-dimensional network. This structure is compared to that of the related disubstituted di-phenyl-phosphino ferrocene.

Tuning of the Coordination and Emission Properties of 4-Amino-2,1,3-Benzothiadiazole by Introduction of Diphenylphosphine Group

A novel amino-benzothiadiazole bearing diphenylphosphine groups (L) was designed and synthesized. A number of its coordination compounds of Cu(I) (1·0.75C7H8, 2a,b), Pd(II) (4), and Pt(II) (5) were...

A Computational Mechanistic Study of the Chemo‐ and Enantioselectivity in the 1,4‐Addition Reaction Catalyzed by a Rh Complex of Sulfinyl‐Phosphine

Computational modelling provides a powerful tool for predicting the possibility of a reaction and permits an important quantitative evaluation of the chemo‐ and enantioselectivities in reactions. Here we present the results of DFT calculations of the chemo‐ and enantioselectivities of the 1,4‐addition of phenylboronic acid to β,γ‐unsaturated α‐ketoamides or α‐ketoesters catalyzed by Rh ligated to a sulfinyl‐phosphine ligand. For the three substrates studied, the predicted chemoselectivity and absolute configuration agree with experimental observations. The ee values calculated at the SMD/M06/DGDZVP level of theory were more accurate than those determined by the IEFPCM/PBE0/DGDZVP method. The high steric pressure exercised by the tBu and diphenylphosphine groups are the origin of the chemo‐ and enantioselectivities of the 1,4‐addition reactions.

Structural elucidation of supported Rh complexes derived from RhCl(PPh3)3 immobilized on surface-functionalized SBA-15 and their catalytic performance for C-heteroatom (S, O) bond formation

The local structures of rhodium complexes derived from the immobilization of Wilkinson’s complex, RhCl(PPh3)3, on SBA-15 silica functionalized with primary–amine, secondary–amine, or diphenylphosphine groups within the mesoporous channels were characterized by a series of techniques including XRD, HR-TEM, multinuclear (13C/29Si/31P) solid-state NMR, 2D 31P{1H} HETCOR NMR, XPS, and Rh K-edge EXAFS. Immobilization of RhCl(PPh3)3 through covalent bond formation with different functional groups grafted to the silica surface lead to variations in the local structure of the Rh center that has important implications for catalysis. The immobilized Rh complexes demonstrated high activity for the addition of alkynes with thiols (hydrothiolation) or sulfonic acids (hydrosulfonation) with excellent regio- and stereoselectivity under mild reaction conditions. This work demonstrates the elucidation of the local structure of the immobilized Rh complexes requires a complimentary multi-technique characterization approach that probes both the metal center itself and surrounding ligands.

Phosphine-functionalized graphene oxide, a high-performance electrocatalyst for oxygen reduction reaction

Here, a new approach for the synthesis of phosphine-functionalized graphene oxide (GO-PPh2) was developed. Using a simple method, diphenylphosphine group was linked to the hydroxyl group of OH-functionalized graphene that existing at the graphene surface. The electrochemical activity of GO-PPh2 for electrochemical oxygen reduction was checked. The results demonstrated that the new carbon hybrid material has a powerful potential for electrochemical oxygen reduction reaction (ORR). Moreover, GO-PPh2 as an electrocatalyst for ORR exhibited tolerance for methanol or ethanol as a result of crossover effect. In comparison with commercial Pt/C and Pt/rGO electrocatalysts, results showed that GO-PPh2 has a much higher selectivity, better durability, and much better electrochemical stability towards the ORR. The proposed method based on GO-PPh2 introduce an efficient electrocatalyst for further application in fuel cells.

Systematic Introduction of Aromatic Rings to Diphosphine Ligands for Emission Color Tuning of Dinuclear Copper(I) Iodide Complexes.

We have newly synthesized two solution-stable luminescent dinuclear copper(I) complexes, [Cu2(μ-I)2(dpppy)2] (Cu-py) and [Cu2(μ-I)2(dpppyz)2] (Cu-pyz), where dpppy = 2,3-bis(diphenylphosphino)pyridine and dpppyz = 2,3-bis(diphenylphosphino)pyrazine, using chelating diphosphine ligands composed of N-heteroaromatic rings. X-ray analysis clearly indicates that the molecular structures of Cu-py and Cu-pyz are almost identical with that of the parent complex, [Cu2(μ-I)2(dppb)2] [Cu-bz; dppb = 2,3-bis(diphenylphosphino)benzene]. Complexes Cu-py and Cu-pyz exhibit luminescence [emission quantum yield (Φem) = 0.48 and 0.02, respectively] in the solid state at 298 K. A wide emission color tuning, from 497 to 638 nm (energy = 0.55 eV, with an emission color ranging from green to reddish-orange), was achieved in the solid state by the introduction of pyridinic N atoms into the bridging phenyl group between the two diphenylphosphine groups. Density functional theory calculations suggest that the emission could originate from the effective combination of the metal-to-ligand charge-transfer excited state with the halide-to-ligand charge-transfer excited state. Thus, the emission color change is due to stabilization of the π* levels of the central aryl group in the diphosphine ligand. Furthermore, these copper(I) complexes exhibit thermally activated delayed fluorescence at 298 K because of the small singlet-triplet energy difference (ΔE = 523 and 564 cm(-1) for Cu-py and Cu-pyz, respectively). The stability of these complexes in chloroform, due to the rigid bonds between the diphosphine ligands and the Cu(I) ions, enables the preparation of emissive poly(methyl methacrylate) films by the solution-doping technique.

Clathrochelates meet phosphorus. New thio- and phosphorylation reactions of an iron(II) dichloroclathrochelate precursor and preparation of its first phosphorus(III)-containing macrobicyclic derivative.

Phosphorylation reactions of an iron(II) dichloroclathrochelate FeBd2(Cl2Gm)(BF)2 (where Bd(2-) and Cl2Gm(2-) are α-benzildioxime and dichloroglyoxime dianions, respectively) with diphenylphosphine oxide and diethyl thiophosphite were performed under phase-transfer conditions. In the case of diethyl thiophosphite as a P-nucleophile, the best yields were obtained in the dichloromethane-50% NaOH aqueous solution-5 mol% triethylbenzylammonium chloride (TEBAC) system. The use of different molar ratios of a macrobicycle precursor and this thiophosphorylating agent allowed us to obtain both the mono- and the diphosphorylated cage complexes. Nucleophilic substitution with diphenylphosphine oxide was performed in the K2CO3-acetonitrile-5 mol% TEBAC system, giving only the corresponding monophosphorylated iron(II) complex in high yield even in the presence of an excess of this P-nucleophile. The phosphorus(v)-containing clathrochelate product was reduced with an excess of silicoform to give an iron(II) macrobicycle with an inherent diphenylphosphine group in an almost quantitative yield, which was then characterized by (31)P{(1)H} NMR and single-crystal X-ray diffraction; it easily undergoes re-oxidation to the initial clathrochelate. The synthesized phosphorus(v)-containing cage complexes were characterized using elemental analysis, MALDI-TOF mass, IR, UV-Vis, (1)H, (11)B, (13)C{(1)H}, (19)F{(1)H} and (31)P{(1)H} NMR spectra, and by single-crystal X-ray diffraction.

Chiral Wide-Bite-Angle Diphosphine Ligands: Synthesis, Coordination Chemistry, and Application in Pd-Catalyzed Allylic Alkylation

A series of diphosphine ligands bearing ester- and ether-modified diphenylether backbones have been prepared. The introduction of carboxylic acid or ether auxiliaries in the ortho-positions relative to the diphenylphosphine groups was achieved via straightforward four-step synthetic protocols, prior to introduction of the phosphines. The electronic properties of these backbone-modified DPEPhos ligands were evaluated by probing the relevant carbonyl stretching frequencies (νCO) of Ni(CO)2(PP) species (PP = diphosphine) using IR spectroscopy and by determining the phosphorus–selenium coupling constant JSe–P of phosphine selenide derivatives using 31P{1H} NMR spectroscopy. Also, the X-ray structure for the bis(carbonyl)nickel(0) species with one of the ligands is reported. The [Pd(η3-allyl)(PP)] complexes were characterized by multinuclear NMR spectroscopy and applied in the asymmetric allylic alkylation of l,3-diphenyl-2-propenyl acetate and cyclohex-2-enyl acetate with dimethyl malonate in order to benchmark their catalytic potential. The enantioselectivity (ranging from 3 to 70%) was found to depend on the size of the chiral auxiliary introduced within the diphenyl ether backbone and its proximity to the phosphorus donor groups and hence to the active metal center.

Unprecedented Calcium Metalla‐macrocycle Having Phosphinoselenoic Amide and Diphenylphosphinate in the Coordination Sphere

AbstractAn eight‐membered calcium metalla‐macrocycle of the composition [Ca{Ph2P(Se)N(Ar)}{Ph2P(O)O}(THF)2]2 (2) (Ar = 2, 6‐dimethylphenyl) can be isolated with a good yield by the reaction of neutral phosphinoselenoic amide [Ph2P(Se)NH(Ar)] (1) and calcium bis(trimethylsilyl)amides [Ca{N(SiMe3)2}2(THF)2] in toluene followed by crystallization in air. The homoleptic calcium phosphinoselenoic amido complex of the composition [Ca{Ph2P(Se)N(Ar)}2(THF)2] (3) can also be obtained through two synthetic routes. In the first route, [Ca{N(SiMe3)2}2(THF)2] is treated with phosphinoselenoic amide [Ph2P(Se)NH(Ar)] (1) at an ambient temperature followed by re‐crystallization in an inert atmosphere to give complex 3 of high purity. In the second route, a one‐pot reaction is carried out involving 1, calcium diiodide, CaI2, and potassium bis(trimethylsilyl)amide [K{N(SiMe3)2}] in toluene in an inert atmosphere. When complex 3 is treated with diphenylphosphinic acid in THF, compound 2 is also obtained with a good yield. Both complexes are confirmed using single‐crystal X‐ray diffraction analysis. The solid‐state structure of complex 2 reveals an eight‐membered macrocycle formed by two diphenylphosphinate groups and two calcium ions. In addition, a four‐membered calcium metallacycle around each calcium atom is formed by the phosphinoselenoic amido ligand through coordination between the nitrogen and selenium atoms. In complex 3, the calcium atom is coordinated by two phosphinoselenoic amido groups and a direct metal selenium bond is observed.

Heterogeneous Silica‐Supported Ruthenium Phosphine Catalysts for Selective Formic Acid Decomposition

AbstractThe water‐soluble ruthenium(II)–mTPPTS complex (mTPPTS=meta‐trisulfonated triphenylphosphine) efficiently catalyzes the generation of hydrogen from formic acid in aqueous solution. This catalyst has been immobilized in a hydrophilic silica support to facilitate mobile portable applications. It was used in diluted formic acid solutions, in which the recycling of a liquid phase catalyst is problematic. A series of heterogenized catalysts have been prepared by the reaction of the ruthenium(II)–mTPPTS dimer and silica functionalized with diphenylphosphine groups via alkyl chains. The length of the alkylene chain separating the silica from the diphenylphosphine group has been varied in these catalysts—all of them catalyzing the decomposition of formic acid. The catalysts were easily separated from the solution and reused. The optimized catalytic system based on MCM41‐Si‐(CH2)2PPh2/Ru‐mTPPTS demonstrated an activity and stability comparable to those of the homogeneous catalyst: a turnover frequency of 2780 h−1 was obtained at 110 °C, and no ruthenium leaching was detected after turnover numbers of 71 000.

1,1′-Bis[bis(4-methoxyphenyl)phosphanyl]ferrocene

In the crystal structure of the title substituted ferrocene complex, [Fe(C19H18O2P)2], the FeII atom lies on a twofold rotation axis, giving an eclipsed cyclo­penta­dienyl conformation with a ring centroid separation of 3.292 (7) Å and an Fe—C bond-length range of 2.0239 (15)–2.0521 (15) Å. In the ligand, the cyclo­penta­dienyl ring forms dihedral angles of 60.36 (6) and 82.93 (6)° with the two benzene rings of the diphenyl­phosphine group, while the dihedral angle between the benzene rings is 67.4 (5)°.

NMR studies of chiral lithium amides with phosphine chelating groups reveal strong Li-P-interactions in ethereal solvents

Chiral lithium amides with a chelating diphenylphosphine group have previously been found to mediate excellent enantioselectivity in the asymmetric addition of alkyllithiums to benzaldehyde. NMR studies reveal for the first time that chiral lithium amides can form chelating dimeric complexes with P-Li interactions in both diethyl ether and THF. The two lithium atoms in the dimer are found to be non-equivalent, one of them is coordinated to two phosphines, detected by Li,P-couplings, while the other lithium is only solvent bound. Slow ethereal ligand exchange on the NMR time scale below –50 °C has been detected by C NMR. Excess of n-butyllithium generates mixed dimeric complexes in both diethyl ether and THF.

Quinolinophane-derived alkyldiphenylphosphines: two homologous P,N-planar chiral ligands for palladium-catalysed allylic alkylation

Two novel homologous [2]paracyclo[2](5,8)quinolinophane-derived P,N-bidentate planar chiral ligands have been synthesised and their effectiveness in asymmetric catalysis tested in palladium-catalysed allylic malonylation of 1,3-diphenylpropenyl acetate. The extent of asymmetric induction depends linearly on the ligand/metal molar ratio, indicating the involvement of P,P-type and chelate P,N-type π-allylpalladium complexes in equilibrium. The length of the chain that binds the diphenylphosphine group to the quinolinophane moiety, while appreciably affecting the P,N-complex stability, has little effect on the extent of asymmetric induction, which is due to the greater reactivity of the [PN]- exo–syn–syn– ([PN] xss) with respect to the [PN]- endo– syn– syn– ([PN] nss) π-allylpalladium complex.

Neutral AuCl complexes supported in linear high molecular weight, poly-spirophosphazene-phosphine copolymers and its conversion to nanostructured gold materials

The reaction under very mild conditions of the polyspirophosphazene copolymer with pendant diphenylphosphine groups {[NP(O2C12H8)]0.85[NP(OC6H4PPh2)2]0.15}n (I) (O2C12H8= 2,2’-dioxybiphenyl) with [Au(THT)Cl] (THT = tetrahydrothiophene) gives the neutral polymeric complex {[NP(O2C12H8)]0.85[NP(OC6H4PPh2-AuCl)2]0.15}n (II). The new material has been characterized by spectrocopic and thermochemical methods (TGA and DSC). Pyrolysis of the Au polymer (I) in air at 800 °C gave gold nanostructured materials that were characterized by TEM, SEM-EDAX and X-ray diffraction. Nanoparticles in the range of 90 to 130 nm were seen.

Chelating phosphines by nucleophilic substitution of fluorine in 3,4,5-trifluorobenzonitrile and tetrafluorophthalonitrile

Directed nucleophilic substitution of two fluorine atoms in title compounds 1, 2 by diphenylphosphine groups was used to prepare new chelating electron-deficient diphosphine ligands 3 and 4 ; the structure of 4 was confirmed by XRD analysis