Bridging Diphosphine Ligands Research Articles

Chromium-based selective ethylene tri-/tetramerization catalysts supported by two-carbon bridged diphosphine ligands

The effect of backbone-substituent of carbon-bridged diphosphine ligands of the type {Ph2PC(COOR)=C(COOR)PPh2} on the catalyst performance in ethylene oligomerization has been explored. The Cr precatalyst supported by the ligand {Ph2PC(COOMe)=C(COOMe)PPh2} (L1) achieved a high activity of 1800 kg/g Cr/h with a total selectivity of 90.8 % toward 1-hexene (77.3 %) and 1-octene (13.5 %) when activated with MMAO-3A. The catalytic system based on these ligands exhibited considerably high thermal stability, maintaining high activity even at 100 oC.

μ-1,2-Bis(dipheylphosphino)ethane-κ2P,P’]bis(3-mercapto-1,2-propanediolato-κS-gold(I))

A new dinuclear gold(I) complex, possessing a bridging diphosphine ligand (1,2-bis(diphenylphosphino)ethane) and two terminal thiol ligands (1-thioglycerol), was synthesized and fully characterized by IR, 1H and 31P NMR, fluorescence, ESI-mass, and diffuse reflection spectroscopy, together with X-ray diffraction and elemental analyses. The compound formed a 1D chain supramolecular structure through intermolecular aurophilic interactions in the crystal structure, leading to photoluminescence in the solid state.

Near-white light emission from single crystals of cationic dinuclear gold(I) complexes with bridged diphosphine ligands.

Three cationic dinuclear Au(I) complexes containing acetonitrile (AN) as an ancillary ligand were synthesized: [μ-LMe(AuAN)2]·2BF4 (1), [μ-LEt(AuAN)2]·2BF4 (2), and [μ-LiPr(AuAN)2]·2BF4 (3) (LMe = {1,2-bis[bis(2-methylphenyl)phosphino]benzene}, LEt = {1,2-bis[bis(2-ethylphenyl)phosphino]benzene}, and LiPr = {1,2-bis[bis(2-isopropylphenyl)phosphino]benzene}). The unique structures of complexes 1-3 with two P-Au(I)-AN rods bridged by rigid diphosphine ligands were determined through X-ray analysis. The Au(I)-Au(I) distances observed for complexes 1-3 were as short as 2.9804-3.0457 Å, indicating an aurophilic interaction between two Au(I) atoms. Unlike complexes 2 and 3, complex 1 incorporated CH2Cl2 into the crystals as crystalline solvent molecules. Luminescence studies in the crystalline state revealed that complexes 1 and 2 mainly exhibited bluish-purple phosphorescence (PH) at 293 K: the former had a PH peak wavelength at 415 nm with the photoluminescence quantum yield ΦPL = 0.12, and the latter at 430 nm with ΦPL = 0.13. Meanwhile, complex 3 displayed near-white PH, that is dual PH with two PH bands centered at 425 and 580 nm with ΦPL = 0.44. The PH spectra and lifetimes of complexes 2 and 3 were measured in the temperature range of 77-293 K. The two PH bands observed for complex 3 were suggested to originate from the two emissive excited triplet states, which were in thermal equilibrium. From theoretical calculations, the dual PH observed for complex 3 is explained to occur from the two excited triplet states, T1H and T1L: the former exhibits a high-energy PH band (bluish-purple) and the latter exhibits a low-energy PH band (orange). The T1H state is considered 3ILCT with a structure similar to that of the S0-optimized structure. Conversely, the T1L state is assumed to be a 3MLCT with a T1-optimized structure, which has a short Au(I)-Au(I) bond and two bent rods (Au-AN). The thermal equilibrium between the two excited states is discussed based on computational calculations and photophysical data in the temperature range of 77-293 K. With regard to the crystal of complex 1, we were unable to precisely measure the temperature-dependent emission spectra and lifetimes, particularly at low temperatures, because the cooled crystals became irreversibly turbid over time.

Solid-state spectroscopic properties of dinuclear cyclometalated Pt(II) complexes with different bridging ligands and anions

Crystal structures of dinuclear cyclometalated Pt(II) complexes with different bridging bis(diphenylphosphino)alkane ligands and counter anions have been compared, and solid-state emissions of crystallite powders and PMMA films doped with luminescent Pt(II) complexes have been investigated. Interestingly, mechanochromic and vapochromic properties are exhibited for solids of dinuclear cyclometalated Pt(II) complex (−)-1 bridged by bis(diphenylphosphino)methane (dppm), and multiple cycles have been repeated without any detectable degradation. However, no distinct stimuli-induced chromism can be observed with the naked eyes for solids of (−)-1 with other counter anions and PMMA films. In addition, with increasing the length of the bridging diphosphine ligand, green-solids without effective intramolecular Pt···Pt contacts have been obtained, and mechanochromic and vapochromic phenomena could not be detected.

Photoluminescent properties and molecular structures of dinuclear gold(I) complexes with bridged diphosphine ligands: near-unity phosphorescence from 3XMMCT/3MC.

The gold(i) complexes [μ-LiPr(AuX)2] {X = Cl (1D), Br (2D), and I (3D); LiPr = 1,2-bis[bis(2-isopropylphenyl)phosphino]benzene} were synthesised to investigate the photoluminescence properties of dinuclear Au complexes comprising weak Au(i)-Au(i) bonds. Single crystals of the tetrahydrofuran (THF) adducts 1DOR, 2DOR, and 3DOR were obtained by recrystallisation of 1D, 2D, and 3D from a mixed solution of THF and n-hexane. These THF adducts afford orange emission, with peak wavelengths ranging from 597 to 630 nm, in the crystalline state at 293 K. Recrystallisation of 3D from a mixed solution of acetone and n-hexane afforded single crystals of the acetone adduct 3DGR, which exhibits blue-green emission at 293 K. No crystals of the acetone adduct were obtained from 1D and 2D. The emission spectra and lifetimes of 1DOR, 2DOR, 3DOR, and 3DGR measured in the temperature range 77-293 K indicate that emission from these complexes in the solid state is due to phosphorescence. Notably, although the molecular structure of 3D in the 3DOR crystal is near-similar to that of 3DGR, the phosphorescence spectrum of 3DOR differs markedly from that of 3DGR, with peak wavelengths at 597 and 506 nm, respectively. Theoretical studies revealed that (1) phosphorescence occurs via the electronic transition from the excited triplet state, which is mainly composed of halogen-to-metal-metal charge transfer and metal-centered transitions and (2) the T1-optimised structure of 3D in the 3DGR crystals differs markedly from that in 3DOR, and the differences in the phosphorescence colour observed between 3DGR and 3DOR are ascribed to the differences in their stabilised structures in the excited triplet state.

Coordination chemistry of the tetraphenyldithioimidodiphosphinate ligand [Ph2P(S)NP(S)Ph2]− and Ph2P(CH2)nPPh2, n = 1, 2, 3 toward ReBr(CO)5

The coordination chemistry of diphosphines dppe, dppm, and dppp towards [Re(CO)4{κ2-S,S′-Ph2P(S)NP(S)Ph2}] was explored. The four types of new complexes prepared depicted monocoordination of the diphosphine or the Ph2P(S)NP(S)Ph2 ligands, bridging diphosphine ligands, and dicoordination to afford the spiro complexes. Characterizations were achieved by IR, mass, NMR (1H, 13C, 31P) spectroscopies, and single-crystal X-ray diffraction.

Synthetic and structural studies of diiron toluenedithiolate complexes coordinated by monophosphine or bridging diphosphine ligands

Five new diiron toluenedithiolate complexes containing monophosphine or diphosphine ligands were prepared and structurally characterized. The reaction of the complex [μ-SC6H3(CH3)S-μ]Fe2(CO)6 (1) with tris(2-furyl)phosphine in the presence of Me3NO·2H2O afforded the monosubstituted complex [μ-SC6H3(CH3)S-μ]Fe2(CO)5[P(2-C4H3O)3] (2) and the disubstituted complex [μ-SC6H3(CH3)S-μ]Fe2(CO)4[P(2-C4H3O)3]2 (3) in 86% and 10% yields, respectively, whereas the reaction of complex 1 with cyclohexyldiphenylphosphine resulted in the formation of the monosubstituted complex [μ-SC6H3(CH3)S-μ]Fe2(CO)5[Ph2PC6H11] (4) in 69% yield. The reactions of complex 1 with 1,2-bis(diphenylphosphino)acetylene or 1,4-bis(diphenylphosphino)butane in the presence of Me3NO·2H2O gave the tetrairon complexes {[μ-SC6H3(CH3)S-μ]Fe2(CO)5}2(Ph2PCCPPh2) (5) and {[μ-SC6H3(CH3)S-μ]Fe2(CO)5}2(Ph2PCH2CH2CH2CH2PPh2) (6), with a bridging diphosphine ligand, in 60% and 56% yields, respectively. The new complexes 2–6 were characterized by elemental analysis and spectroscopy, as well as by X-ray crystallography.

Synthesis and structures of diiron dithiolate complexes with 1,2-bis(diphenylphosphino)acetylene or tris(2-methoxyphenyl)phosphine

Treatment of the diiron hexacarbonyl complexes (μ-SCH2CH2CH2S-μ)Fe2(CO)6 or [μ-SCH(CH3)CH(CH3)S-μ]Fe2(CO)6 with 1,2-bis(diphenylphosphino)acetylene in the presence of Me3NO·2H2O afforded tetrairon complexes with a bridging diphosphine ligand [(μ-SCH2CH2CH2S-μ)Fe2(CO)5]2(Ph2PCCPPh2) (1) and {[μ-SCH(CH3)CH(CH3)S-μ]Fe2(CO)5}2(Ph2PCCPPh2) (2). Diiron pentacarbonyl complexes with a monophosphine ligand, (μ-SCH2CH2S-μ)Fe2(CO)5[P(C6H4OCH3-2)3] (3) and [μ-SC6H3(CH3)S-μ]Fe2(CO)5[P(C6H4OCH3-2)3] (4), were prepared by the reactions of (μ-SCH2CH2S-μ)Fe2(CO)6 or [μ-SC6H3(CH3)S-μ]Fe2(CO)6 with tris(2-methoxyphenyl)phosphine in the presence of Me3NO·2H2O. The new complexes 1–4 were characterized by elemental analysis and spectroscopy, as well as by single crystal X-ray diffraction analysis.

Anion Directed Self‐Assembly of One‐Dimensional and Two‐Dimensional Coordination Polymers Containing Bridging Diphosphine Ligands

AbstractThe reactions of 1,2‐bis(diphenylphosphanyl)ethane (dppe) with different silver(I) salts facilitated the formation of 1D and 2D coordination polymers, [Ag(dppe)(OAc)]n·nH2O (1) and [Ag2(dppe)1.5(NO3)2]n (2), respectively. The complexes were characterized by elemental analysis, ATR‐IR spectroscopy, 1H NMR, 13C NMR, and 31P NMR spectroscopy, and single‐crystal X‐ray diffraction. Structural analysis revealed that complex 1 exhibits a 1D infinite wavy structure, in which each silver(I) ion is bridged by dppe ligands. Structure 2 has a 2D topologically promising architecture that displays a 6.6.6 graphitic net, which corresponds to hnd topology. The nitrate ions and dppe ligands are in a μ2 bridging mode and support the formation of this net. Moreover, significant π–π interactions between the phenyl rings in the apertures of (6,3) grid stabilized complex 2.

Mono- and binuclear orthopalladated complexes of phosphorus ylides containing nitrogen, phosphorus or bridging diphosphine ligands: Self-assembly, theoretical calculations and comparative catalytic activity

Binuclear orthopalladated complexes of phosphorus ylides containing electron-withdrawing fluoro (Y1), bromo (Y2) or phenyl (Y3) substituent, [Pd{κ2(C,C)-[(C6H4-2)PPh2]CH(CO)C6H4X-4}(μ-Cl)]2 (X = F (1), Br (2), Ph (3)) were obtained by two different methods from the reaction of corresponding ylides and PdCl2 or Pd(OAc)2. The synthesized orthopalladated complexes 1 and 2 reacted with the monodentate ligands with various donor abilities affording the mononuclear complexes [PdCl{C,C-{CH[P(C6H4-2)Ph2]C(O)C6H4X-4]}}L] [L = triphenylphosphine (X = Cl (1a), X = Br (2a)); 3-methylpyridine (X = Cl (1b), X = Br (2b)); 4-methylpyridine (X = Br (2c)); 2,4,6-trimethylpyridine (X = Cl (1c)); pyridine (X = Cl (1d)); piperidine (X = Cl (1e)). The reaction of chloro-bridged complex 3 with bis(diphenylphosphino)ethane, dppe, and bis(diphenylphosphino)propane, dppp, in the 1:1 ratio occurred to give the symmetrical bridged complexes of general formula [Pd2Cl2{C,C-{CH[P(C6H4-2)Ph2]C(O)C6H4X-4]}2}}(μ-PˆP)] (PˆP = dppe (3a) and dppp (3b)). New complexes were fully characterized by elemental analysis, IR and NMR spectroscopies. The crystal structures of 1, 1a, 2a, 3 and 3a were determined by single-crystal X-ray diffraction analysis that revealed the self-assembly of complexes via the short contacts between donor and acceptor groups to form polymer, sheet or network supramolecular structures. Density functional theory (DFT) calculations for complexes 1, 1a and 2a indicated the good agreement with the experimental value reported in this work. The catalytic activity of 1, 1a and 2a were comparatively studied in the Suzuki cross-coupling reactions which showed the more efficiency of mononuclear complex 1a with fluoro substituent.

Reaction of Triangular Cluster Complex Triiron Enneacarbonyl Disulfide with 1,2-bis(diphenylphosphino)ethane

Reaction of Fe3(μ3-S)2(CO)9 (A) with 1,2-bis(diphenylphosphino)ethane (Ph2PCH2CH2PPh2, dppe) in the presence of the decarbonylating agent Me3NO·2H2O in MeCN at room temperature afforded [Fe3(μ3-S)2(CO)8]2(Ph2PCH2CH2PPh2) (1) containing bridging diphosphine ligand in 50% yield. The title complex 1 was structurally characterized by IR and NMR spectroscopic analysis. In addition, the molecular structure of 1 was further determined by X-ray crystallography. The molecule is centrosymmetric and the phosphorus atoms of DPPE reside in a basal position of the square-pyramidal geometry of the iron atoms.

ChemInform Abstract: Dinuclear N‐Heterocyclic Carbene Palladium(II) Complexes as Efficient Catalysts for the Buchwald—Hartwig Amination.

Abstract A series of dinuclear N-heterocyclic carbene (NHC) palladium complexes [PdCl2(NHC)]2(μ-L) (1–6, L = diphosphine ligands) has been synthesized and fully characterized by 1H NMR, 13C NMR and 31P NMR spectroscopies, elemental analysis, IR spectroscopy, and X-ray crystal structural study. The solid-state structures of 1–6 show dinuclear frameworks with two palladium(II) centres were held together by bridging diphosphine ligands. Each palladium centre was coordinated by an N-heterocyclic carbene ligand, a phosphorus atom and two chloro ions in a trans-arrangement. Further explorations of the catalytic potential of the dinuclear carbene palladium complexes as catalysts for Pd-mediated transformations have been examined under microwave irradiation conditions and the title complexes (1–6) displayed good catalytic activities in Buchwald–Hartwig aminations of aryl chlorides.

Assembly, structure, and reactivity of Cu₄S and Cu₃S models for the nitrous oxide reductase active site, Cu(Z)*.

Bridging diphosphine ligands were used to facilitate the assembly of copper clusters with single sulfur atom bridges that model the structure of the Cu(Z)* active site of nitrous oxide reductase. Using bis(diphenylphosphino)amine (dppa), a [Cu(I)4(μ4-S)] cluster with N-H hydrogen bond donors in the secondary coordination sphere was assembled. Solvent and anion guests were found docking to the N-H sites in the solid state and in the solution phase, highlighting a kinetically viable pathway for substrate introduction to the inorganic core. Using bis(dicyclohexylphosphino)methane (dcpm), a [Cu(I)3(μ3-S)] cluster was assembled preferentially. Both complexes exhibited reversible oxidation events in their cyclic voltammograms, making them functionally relevant to the Cu(Z)* active site that is capable of catalyzing a multielectron redox transformation, unlike the previously known [Cu(I)4(μ4-S)] complex from Yam and co-workers supported by bis(diphenylphosphino)methane (dppm). The dppa-supported [Cu(I)4(μ4-S)] cluster reacted with N3(-), a linear triatomic substrate isoelectronic to N2O, in preference to NO2(-), a bent triatomic. This [Cu(I)4(μ4-S)] cluster also bound I(-), a known inhibitor of Cu(Z)*. Consistent with previous observations for nitrous oxide reductase, the tetracopper model complex bound the I(-) inhibitor much more strongly and rapidly than the substrate isoelectronic to N2O, producing unreactive μ3-iodide clusters including a [Cu3(μ3-S)(μ3-I)] complex related to the [Cu4(μ4-S)(μ2-I)] form of the inhibited enzyme.

Dinuclear N-heterocyclic carbene palladium(II) complexes as efficient catalysts for the Buchwald–Hartwig amination

A series of dinuclear N-heterocyclic carbene (NHC) palladium complexes [PdCl2(NHC)]2(μ-L) (1–6, L = diphosphine ligands) has been synthesized and fully characterized by 1H NMR, 13C NMR and 31P NMR spectroscopies, elemental analysis, IR spectroscopy, and X-ray crystal structural study. The solid-state structures of 1–6 show dinuclear frameworks with two palladium(II) centres were held together by bridging diphosphine ligands. Each palladium centre was coordinated by an N-heterocyclic carbene ligand, a phosphorus atom and two chloro ions in a trans-arrangement. Further explorations of the catalytic potential of the dinuclear carbene palladium complexes as catalysts for Pd-mediated transformations have been examined under microwave irradiation conditions and the title complexes (1–6) displayed good catalytic activities in Buchwald–Hartwig aminations of aryl chlorides.

A binuclear gold(I) complex with mixed bridging diphosphine and bis(N-heterocyclic carbene) ligands shows favorable thiol reactivity and inhibits tumor growth and angiogenesis in vivo.

In the design of anticancer gold(I) complexes with high in vivo efficacy, tuning the thiol reactivity to achieve stability towards blood thiols yet maintaining the thiol reactivity to target cellular thioredoxin reductase (TrxR) is of pivotal importance. Herein we describe a dinuclear gold(I) complex (1-PF6) utilizing a bridging bis(N-heterocyclic carbene) ligand to attain thiol stability and a diphosphine ligand to keep appropriate thiol reactivity. Complex 1-PF6 displays a favorable stability that allows it to inhibit TrxR activity without being attacked by blood thiols. In vivo studies reveal that 1-PF6 significantly inhibits tumor growth in mice bearing HeLa xenograft and mice bearing highly aggressive mouse B16-F10 melanoma. It inhibits angiogenesis in tumor models and inhibits sphere formation of cancer stem cells in vitro. Toxicology studies indicate that 1-PF6 does not show systemic anaphylaxis on guinea pigs and localized irritation on rabbits.

A Binuclear Gold(I) Complex with Mixed Bridging Diphosphine and Bis(N‐Heterocyclic Carbene) Ligands Shows Favorable Thiol Reactivity and Inhibits Tumor Growth and Angiogenesis In Vivo

AbstractIn the design of anticancer gold(I) complexes with high in vivo efficacy, tuning the thiol reactivity to achieve stability towards blood thiols yet maintaining the thiol reactivity to target cellular thioredoxin reductase (TrxR) is of pivotal importance. Herein we describe a dinuclear gold(I) complex (1‐PF6) utilizing a bridging bis(N‐heterocyclic carbene) ligand to attain thiol stability and a diphosphine ligand to keep appropriate thiol reactivity. Complex 1‐PF6 displays a favorable stability that allows it to inhibit TrxR activity without being attacked by blood thiols. In vivo studies reveal that 1‐PF6 significantly inhibits tumor growth in mice bearing HeLa xenograft and mice bearing highly aggressive mouse B16‐F10 melanoma. It inhibits angiogenesis in tumor models and inhibits sphere formation of cancer stem cells in vitro. Toxicology studies indicate that 1‐PF6 does not show systemic anaphylaxis on guinea pigs and localized irritation on rabbits.

Synthesis, Characterization, and Luminescence Studies of Discrete Polynuclear Gold(I) Sulfido and Selenido Complexes with Intramolecular Aurophilic Contacts

The synthesis, characterization, and photophysical and photochemical properties of a family of high-nuclearity gold(I) chalcogenides, specifically, the gold(I) sulfido and selenido complexes containing different bridging diphosphine ligands with nuclearities of ten ([Au10{μ-Ph2PN(R)PPh2}4(μ3-E)4](2+)) and six ([Au6{μ-Ph2PN(R)PPh2}3(μ3-E)2](2+)), are reported. The X-ray crystal structures of the complex cations of Au10 and Au6 are found to be propeller-like structures and distorted cubane structures, respectively, with the presence of short intramolecular gold···gold distances. The complexes show intense green and/or orange phosphorescence upon photoexcitation in the solid state and in solution at ambient and low temperature. The emission properties are found to be strongly dependent on the nuclearities and the chalcogenido ligands, but are rather insensitive to the substituents on the bis(diphenylphosphino)amines. The emissions are tentatively assigned to originate from the excited states derived from the phosphine-centered intraligand (IL) transition or metal-centered (ds/dp) mixed with ligand-to-metal-metal charge transfer (LMMCT) (E→Au) transition. The photochemical properties of the complexes were also studied by transient absorption spectroscopy.

Backbone modified small bite-angle diphosphines: Synthesis, structure, and DFT evaluation of the thermal activation products based on Os3(CO)10{μ-Ph2PC(Me)2PPh2}

Addition of 2,2'-bis(diphenylphosphino)propane, Ph2PC(Me)2PPh2 (dppmMe2), to Os3(CO)10(MeCN)2 at room temperature affords Os3(CO)10{μ-Ph2PC(Me)2PPh2} (1-Me2), whose X-ray diffraction has been established and found to contain a bridging diphosphine ligand. Heating 1-Me2 in toluene results in the formation of the expected orthometalated addition product Os3(CO)8{μ3-Ph2PC(Me)2P(Ph)C6H4}(μ-H) (2-Me2) in only trace amounts, with the face-capped cluster Os3(CO)9{μ3-PhPC(Me)2P(Ph)C6H4} (3-Me2) formed as the major product as a result of elimination of benzene. The conversion of 1-Me2 to 2-Me2 has been investigated by density functional theory (DFT) calculations and the potential energy surface has been mapped out. The observed reactivity in the dppmMe2-substituted cluster 1-Me2 is compared with the related dppmH2- and dppmHMe-substituted triosmium complexes.

Reactions of mixed-metal dicobalt–iron cluster (μ3-S)FeCo2(CO)9 with diphosphine ligands

Four new dicobalt–iron cluster complexes with bridging or chelating diphosphine ligands have been prepared and structurally characterized. Treatment of (μ3-S)FeCo2(CO)9 (A) with Ph2PCH2CH2PPh2 at room temperature in CH2Cl2 resulted in formation of [(μ3-S)FeCo2(CO)8]2(Ph2PCH2CH2PPh2) (1) and (μ3-S)FeCo2(CO)7(Ph2PCH2CH2PPh2) (2) with bridging diphosphine ligand in 12% and 56% yields, respectively, whereas (μ3-S)FeCo2(CO)7(cis-Ph2PCHCHPPh2) (3) with chelating diphosphine ligand was produced by reaction of A with cis-Ph2PCHCHPPh2 in 88% yield. In addition, (μ3-S)FeCo2(CO)7(Ph2PCH2PPh2) (4) with bridging diphosphine ligand could be obtained by reaction of A with Ph2PCH2PPh2 in 69% yield. The new complexes 1–4 were characterized by elemental analysis, spectroscopy and X-ray crystallography.

Synthesis and structural characterization of dicobalt–iron clusters containing bridging diphosphine ligands

Reaction of (μ 3-S)FeCo2(CO)9 with N-substituted bis(diphenylphosphanyl)amine Ph2PN(R)PPh2 (R = CH2CH2CH3, A; CH2Ph, B) at room temperature in CH2Cl2 afforded dicobalt–iron cluster complexes (μ 3-S)FeCo2(CO)7[Ph2PN(R)PPh2] (R = CH2CH2CH3, 1; CH2Ph, 2) in 75% and 66% yields, respectively. 1 and 2 were characterized by elemental analysis and spectroscopy. In addition, the molecular structures of A, 1, and 2 were determined by single crystal X-ray diffraction analysis.