Bulky Terphenyl Research Articles

A crystalline stannyne.

The synthesis of heteronuclear alkyne analogues incorporating heavier group 14 elements (R1-C≡E-R2, E = Si, Ge, Sn, Pb) has posed a long-standing challenge. Neutral silynes (R1-C≡Si(L)-R2) and germynes (R1-C≡Ge(L)-R2) stabilized by a Lewis base have achieved sufficient stability for structural characterization at low temperatures. Here we show the isolation of a base-free stannyne (R1-C≡Sn-R2) at room temperature, achieved through the strategic use of a bulky cyclic phosphino ligand in combination with a bulky terphenyl substituent. Despite an allenic structure with strong delocalization of π-electrons, this compound exhibits adjacent ambiphilic carbon and tin centres, forming a carbon-tin multiple bond with ionic character. The stannyne demonstrates reactivity similar to carbenes or stannylenes, reacting with 1-adamantyl isocyanide and 2,3-dimethyl-1,3-butadiene. Additionally, its carbon-tin bond can be saturated by Et3N·HCl or cleaved by isopropyl isocyanate.

Tuning the Inorganic Core of a reduced Ni2Ge2 Cluster.

Tetranuclear cores (M-E)2 of transition metals (M) and tetrylenes (EII=Si, Ge, Sn) are key motifs in homogeneous and heterogeneous catalysis. They exhibit a continuum of M-M and E-E bonding within the inorganic core that leads to a variety of structures for which there are no specific synthetic methods. Herein, we report a series of highly reduced [Ni0GeII]2 squares solely stabilized by bulky terphenyl (C6H3-2,6-Ar2) ligands, for which we provide complementary and high-yielding syntheses. Reactivity studies with common Lewis bases (carbene and CO) evince that the structure of the (M-E)2 core can be transformed. We have investigated this core modification by computational means, offering a rationale to better understand the continuum of bonding across these clusters.

Realization of Long Operational Lifetimes in Vacuum-Deposited Organic Light-Emitting Devices Based on para-Substituted Pyridine Carbazolylgold(III) C^C^N Complexes.

A new series of robust C^C^N carbazolylgold(III) complexes is designed and synthesized through the introduction of inert and sterically bulky oligophenyl substituents on the pyridyl moiety of the cyclometalating ligand. High photoluminescence quantum yields of up to 96% are recorded with these complexes doped in solid-state thin films, and short excited-state lifetimes of 0.3 μs or less in the solid state at room temperature are found. Promising electroluminescence (EL) performances are shown by the vacuum-deposited organic light-emitting devices (OLEDs) based on this series of gold(III) complexes. High external quantum efficiencies of up to 19.5% with efficiency roll-offs of down to 10% at a practical luminance brightness level of 1000 cd m-2 are achieved. More importantly, record-long operational lifetimes (LT50) of up to 470,700 h at 100 cd m-2 are realized, which is currently the highest value among all classes of gold(III) complexes with tridentate pincer ligands. Particularly, by introducing a sterically bulky terphenyl moiety on the reactive site of the pyridine ring, the LT50 value is shown to attain ∼7 times longer half-lifetime than that based on the unsubstituted complex. These unprecedented EL performances and the simple synthetic route in a mercury-free fashion make them promising emitting materials for practical OLEDs toward commercialization.

Photocyclization reaction and related photodynamics in the photoproducts of a tetraphenylethylene derivative with bulky substituents: unexpected solvent viscosity effect.

Tetraphenylethylene (TPE) derivatives are ones of the most versatile building blocks showing aggregation-induced emission (AIE). However, their applications are limited by the photophysical and photochemical processes that occur in their excited state. Herein, we report a detailed study of the photochemical behaviour of a new TPE derivative with bulky terphenyl groups (TTECOOBu) in solvents of different viscosities and in a PMMA film. UV light irradiation shows an efficient photocyclization reaction, which produces a 9,10-diphenylphenanthrene (DPP) derivative photoproduct. The emission spectra of the irradiated samples show intermediate (∼420 nm) and final (∼380 nm) species. The photocyclization events are more efficient in environments of higher viscosities or rigidity. We show that in a photoirradiated PMMA film containing TTECOOBu, it is possible to etch a message for more than 1 year. The kinetics is dictated by the motions of the phenyl rings and is faster when their motions are precluded or inhibited. We also elucidated the femto- to millisecond photodynamics of the intermediate and final photoproducts and provide a full picture of their relaxation, with the latter in ∼1 ns at S1 and ∼1 μs at T1. We also demonstrate that the kinetics of the bulky TTECOOBu is much slower than that of the TPE core. Our results also show that both photoevents are not reversible contrary to the case of TPE kinetics. We believe that these results will shed more light on the photochemical behaviour of TPE derivatives and should help in the development of novel TPE-based materials with improved photostability and photo-properties.

Novel blue-phosphorescent platinum(II) ternary complexes with β-diketonate and fluorinated phenylimidazole for organic light-emitting diodes

In this study, the one-pot synthesis of two novel Pt(II) β-diketonate compounds, namely Pt(tpim)(O^O) (1) and Pt(mtpim)(O^O) (2) (tpim = 1-([1,1′:3′,1′′-terphenyl]-2′-yl)-2-(4-fluorophenyl)-1 H-imidazole, mtpim = 2-(4-fluorophenyl)-1-(5′-methyl-[1,1′:3′,1′′-terphenyl]-2′-yl)-1 H-imidazole, and O^O = acetylacetonato), was achieved. Both compounds had a distorted square-planar geometry without direct intermolecular Pt(II)—Pt(II) interactions, which was attributed to the bulky terphenyl group of the C^N chelate as well as strong intermolecular Pt(II)—H(terphenyl/imidazole) interaction. Compounds 1 and 2 exhibited bright sky-blue-phosphorescent emission with a λmax = 490 nm and photoluminescence quantum yields of 0.50 and 0.47, respectively. The time-dependent density functional theory calculations revealed that the electronic transitions of both compounds were attributed to the combination of intraligand charge transfer (π(phenylimidazole)–π*(terphenyl)) and ligand-to-ligand charge transfer (π(acac)–π*(terphenyl)), in addition to a contribution from the metal-to-ligand charge transfer (Ptd–π*(terphenyl)). Compounds 1 and 2, as the dopants, and 3′-di(9 H-carbazol-9-yl)-1,1′-biphenyl:9-(3'-carbazol-9-yl-5-cyano-biphenyl-3-yl)-9 H-carbazole-3-carbonitrile, as the mixed host were used to fabricate multilayer phosphorescent organic light-emitting diodes. Compound 1 doped in the emissive layer at a 10% doping level demonstrated a maximum current efficiency of 21.7 cd A−1 at 100 cd m−2.

Access to Monomeric Lead(II) Hydrides with Remarkable Thermostability and Their Use in Catalytic Hydroboration of Carbonyl Derivatives.

We report on the remarkable stability of unprecedented, monomeric lead(II) hydrides M+[LPb(II)H]- (M[1-H]), where L = 2,6-bis(3,5-diphenylpyrrolyl)pyridine and M = (18-crown-6)potassium or ([2.2.2]-cryptand)potassium. The half-life of [K18c6][1-H] of ∼2 days in tetrahydrofuran at 25 °C is significantly longer than those reported for dimeric lead(II) hydrides supported by bulky terphenyl ligands (few hours at low temperatures), which are the only examples known for lead(II) hydride compounds. The presence of a Pb-H bond in [1-H]- was unambiguously identified by multinuclear NMR spectroscopy. Remarkably, a 1H resonance of the hydride ligand was found at δ = 41.43 ppm (1JPbH = 1312 Hz). For reactivity study, [1-H]- serves as an excellent hydroboration catalyst with high turnover numbers and turnover frequencies for several carbonyl compounds.

LPdCl2(amine) complexes supported by terphenyl phosphanes: applications in aryl amination reactions.

Despite the excellent catalytic properties display by NHC-Pd-PEPPSI complexes in cross-coupling, phosphane analogs have been barely screened. In this work, we report the synthesis and characterization of a series of LPdCl2(amine) complexes bearing dialkylterphenyl phosphanes (PR2Ar') and pyridine or morpholine ligands. The novel compounds have been tested as precatalysts in aryl amination reactions. The complex [(PCyp2ArXyl2)PdCl2(morpholine)] shows the best catalytic activity allowing the room-temperature coupling of aryl bromides and chlorides with aniline.

Zero-valent ML2 complexes of group 10 metals supported by terphenyl phosphanes.

Bulky terphenyl phosphane ligands PMe2Ar' (Ar' = terphenyl group) facilitate the isolation of zero-valent bis-phosphane complexes of nickel, palladium and platinum. The former show coordination numbers greater than two in the solid state due to the existence of Ni-Carene interactions with the terphenyl fragment.

Correction: α-Diimine nickel complexes bearing axially bulky terphenyl and equatorially bulky dibenzobarrelene groups: synthesis, characterization and olefin polymerization studies

Correction for ‘α-Diimine nickel complexes bearing axially bulky terphenyl and equatorially bulky dibenzobarrelene groups: synthesis, characterization and olefin polymerization studies’ by Xiaohua Wang et al., Polym. Chem., 2020, 11, 6783–6793, DOI: 10.1039/D0PY01152E.

Dialkylterphenyl Phosphine-Based Palladium Precatalysts for Efficient Aryl Amination of N-Nucleophiles.

A series of 2-aminobiphenyl palladacycles supported by dialkylterphenyl phosphines, PR2 Ar' (R=Me, Et, iPr, Cyp (cyclopentyl), Ar'=ArDipp2 , ArXyl2f , Dipp (2,6-C6H3-(2,6-C6H3-(CHMe2)2)2), Xyl=xylyl) have been prepared and structurally characterized. Neutral palladacycles were obtained with less bulky terphenyl phosphines (i.e., Me and Et substituents) whereas the largest phosphines provided cationic palladacycles in which the phosphines adopted a bidentate hemilabile k1 -P,η1 -Carene coordination mode. The influence of the ligand structure on the catalytic performance of these Pd precatalysts was evaluated in aryl amination reactions. Cationic complexes bearing the phosphines PiPr2 ArXyl2 and PCyp2 ArXyl2 were the most active of the series. These precatalysts have demonstrated a high versatility and efficiency in the coupling of a variety of nitrogen nucleophiles, including secondary amines, alkyl amines, anilines, and indoles, with electronically deactivated and ortho-substituted aryl chlorides at low catalyst loadings (0.25-0.75 mol % Pd) and without excess ligand.

α-Diimine nickel complexes bearing axially bulky terphenyl and equatorially bulky dibenzobarrelene groups: synthesis, characterization and olefin polymerization studies

A new family of asymmetric α-diimine nickel complexes bearing axially and equatorially bulky groups were synthesized successfully. They exhibited high catalytic activities for ethylene polymerization and afforded ultra-high-molecular-weight elastomeric polyethylenes.

A new strategy to synthesize three-coordinate mononuclear copper(i) halide complexes containing a bulky terphenyl bidentate phosphine ligand and their luminescent properties

Three mononuclear three-coordinate Cu(i) halide complexes were synthesized by a new strategy and they exhibit green to yellow green emission in the solid state at room temperature.

Steric and Electronic Properties of the Bulky Terphenyl Ligand ArtBu6 (ArtBu6 = C6H3-2,6-(C6H2-2,4,6-tBu3)2) and Synthesis of Its Tin Derivatives ArtBu6SnCl, ArtBu6SnSn(H)2ArtBu6, and ArtBu6SnSnArtBu6: A New Route to a Distannyne via Thermolysis of the Asymmetric Hydride ArtBu6SnSn(H)2ArtBu6

A larger scale, modified synthesis of the bulky terphenyl ligand iodo precursor ArtBu6I (1; ArtBu6 = C6H3-2,6-(C6H2-2,4,6-tBu3)2), featuring six tert-butyl groups on the flanking aryl rings, and the synthesis of its tin derivatives ArtBu6SnCl (2), ArtBu6SnSn(H)2ArtBu6 (3), and ArtBu6SnSnArtBu6 (4) are described. For the key reagent ArtBu6I (1), recently reported by Schrock, Hoyveda, and co-workers, modifications to the synthesis using the easily prepared Grignard reagent EtMgBr to obtain ArtBu6MgX, as well as use of their published trituration and iodination protocols in hexane, allowed isolation of ca. 80 g quantities of ArtBu6I (1). The tin(II) halide derivative 2 and the unsymmetrical hydride 3 were synthesized by salt metathesis and reduction with DIBAL (iBu2AlH), respectively. The distannyne 4 was obtained by a new synthetic route by the dehydrogenation of 3 at 100 °C in toluene. It was also synthesized by reduction of 2 with KC8. All compounds were characterized using single-crystal X-ray diffractio...

Counterintuitive Interligand Angles in the Diaryls E{C6H3-2,6-(C6H2-2,4,6-iPr3)2}2 (E = Ge, Sn, or Pb) and Related Species: The Role of London Dispersion Forces

The straightforward reaction of two equivalents of the lithium salt of the bulky terphenyl ligand Li(OEt2)C6H3-2,6-(C6H2-2,4,6-iPr3)2 with suspensions of GeCl2·dioxane, SnCl2, or PbBr2 in diethyl ether resulted in the isolation of the very crowded σ-bonded diaryl tetrylenes of formula E{C6H3-2,6-(C6H2-2,4,6-iPr3)2}2 (E = Ge (1), Sn (2), Pb (3)) as blue crystalline solids. Despite their high level of steric congestion, X-ray crystallography showed that compounds 1–3 possess Cipso–E–Cipso interligand bond angles in the range 107.61–112.55°, which are narrower than those observed in analogous species with less bulky terphenyl substituents. Compounds 1–3 were characterized by 1H, 13C{1H} (1–3), and 119Sn{1H} (2) NMR spectroscopy, whereas solution 207Pb{1H} NMR spectroscopy of 3 has not yet afforded a signal under ambient conditions. FT-IR and UV–vis spectra of 1–3 were also recorded. The relatively narrow interligand angles displayed by 1–3 are attributed in part to the increase in London dispersion force int...

Extremely Bulky Amido First Row Transition Metal(II) Halide Complexes: Potential Precursors to Low Coordinate Metal–Metal Bonded Systems

Reactions of the extremely bulky potassium amide complexes, [KL'(η(6)-toluene)] or [KL"] (L'/L" = N(Ar*)(SiR3), Ar* = C6H2{C(H)Ph2}2Me-2,6,4; R = Me (L') or Ph (L")), with a series of first row transition metal(II) halides have yielded 10 rare examples of monodentate amido first row transition metal(II) halide complexes, all of which were crystallographically characterized. They encompass the dimeric, square-planar chromium complexes, [{CrL'(THF)(μ-Cl)}2] and [{CrL"(μ-Cl)}2], the latter of which displays intramolecular η(2)-Ph···Cr interactions; the dimeric tetrahedral complexes, [{ML'(THF)(μ-Br)}2] (M = Mn or Fe), [{ML"(THF)(μ-X)}2] (M = Mn, Fe or Co; X = Cl or Br) and [{CoL"(μ-Cl)}2] (which displays intramolecular η(2)-Ph···Co interactions); and the monomeric zinc amides, [L'ZnBr(THF)] (three-coordinate) and [L"ZnBr] (two-coordinate). Solution state magnetic moment determinations on all but one of the paramagnetic compounds show them to be high-spin systems. Throughout, comparisons are made with related bulky terphenyl transition metal(II) halide complexes, and the potential for the use of the prepared complexes as precursors to low-valent transition metal systems is discussed.

The N,N‐Bis(terphenyl)aminophosphenium Cation – A Sensitive Probe for Interactions with Different Anions

AbstractA series of salts that contain the terphenyl‐substitutedbis(amino)phosphenium cation with different anions (F–,Cl–, [CF3CO2]–, [CF3SO3]–, [B(C6F5)4]–, [GaCl4]–, [SbF6]–, [Al{OCH(CF3)2}4]– and [CHB11H5Br6]–) has been prepared by different synthetic protocols. All of the products have been characterised spectroscopically and by single‐crystal X‐ray diffraction studies. A detailed analysis of the interionic interactions and their influence on the molecular structure of the phosphenium cation reveals a strong dependence on the capability of the anion to enter the pocket generated by the bulky terphenyl substituents.

ChemInform Abstract: Transition Metal Complexes Stabilized by Bulky Terphenyl Ligands: Application to Metal—Metal Bonded Compounds

AbstractReview: 190 refs.

Enhanced Photoluminescence, Mesomorphism and Conformation of Liquid-Crystalline Conjugated Polymers with Terphenyl Mesogen Pendants

A variety of LCCPs containing terphenyl pendants based on polyacetylene, polythiophene, poly(p-phenylene) and a poly(p-phenylene) copolymer backbone have been synthesized. The effects of the structural variation on their properties, especially their mesomorphism, photoluminescence and secondary structures, were studied systematically. Longer alkoxy spacer favor stronger light emission and better mesomorphism. Disubstituted polyacetylenes show better developed mesomorphic textures, higher quantum yields and better thermal stability than their corresponding monosubstituted analogs. Steric effects and the “jacket- effect” from the mesogens cause the bulky terphenyl mesogen pendants to rotate around the main chain and force the main chain to assume a spiral conformation along the main chain in long range.

Methyl-Bridged Transition Metal Complexes (M = Cr−Fe) Supported by Bulky Terphenyl Ligands

The synthesis and characterization of a series of divalent terphenyl transition metal methyl complexes {ArM(μ-Me)}2 (M = Cr (1), Ar = C6H-2,6-(C6H2-2,4,6-iPr3)2-3,5-iPr2, abbreviated as 3,5-iPr2-Ar*; M = Mn (2), Fe (3), Ar = C6H3-2,6-(C6H2-2,4,6-iPr3)2, abbreviated as Ar*) as well as a phenyl-bridged iron complex {Ar*Fe(μ-Ph)}2 (4) are described. Complexes 1−4 were prepared by reaction of the corresponding terphenyl metal halide with LiMe or LiPh and have dimeric structures, in which three-coordinate metals are bridged by methyl or phenyl groups. Each chromium atom in 1 features a further interaction with the ipso-carbon of the flanking aryl ring; while the manganese and iron atoms in 2 and 3 have distorted trigonal-planar geometry. Complexes 1−4 are rare examples of low-coordinate transition metal complexes of methyl or phenyl groups, and they were characterized by X-ray crystallography, NMR, and UV−vis spectroscopy, elemental analysis, and magnetic measurements.

Substituent Effects in Formally Quintuple-Bonded ArCrCrAr Compounds (Ar = Terphenyl) and Related Species

The effects of different terphenyl ligand substituents on the quintuple Cr-Cr bonding in arylchromium(I) dimers stabilized by bulky terphenyl ligands (Ar) were investigated. A series of complexes, ArCrCrAr (1-4; Ar = C6H2-2,6-(C6H3-2,6-iPr2)2-4-X, where X = H, SiMe3, OMe, and F), was synthesized and structurally characterized. Their X-ray crystal structures display similar trans-bent C(ipso)CrCrC(ipso) cores with short Cr-Cr distances that range from 1.8077(7) to 1.8351(4) A. There also weaker Cr-C interactions [2.294(1)-2.322(2) A] involving an C(ipso) of one of the flanking aryl rings. The data show that the changes induced in the Cr-Cr bond length by the different substituents X in the para positions of the central aryl ring of the terphenyl ligand are probably a result of packing rather than electronic effects. This is in agreement with density functional theory (DFT) calculations, which predict that the model compounds (4-XC6H4)CrCr(C6H4-4-X) (X = H, SiMe3, OMe, and F) have similar geometries in the gas phase. Magnetic measurements in the temperature range of 2-300 K revealed temperature-independent paramagnetism in 1-4. UV-visible and NMR spectroscopic data indicated that the metal-metal-bonded solid-state structures of 1-4 are retained in solution. Reduction of (4-F3CAr')CrCl (4-F3CAr' = C6H2-2,6-(C6H3-2,6-iPr2)2-4-CF3) with KC8 gave non-Cr-Cr-bonded fluorine-bridged dimer {(4-F3CAr')Cr(mu-F)(THF)}2 (5) as a result of activation of the CF3 moiety. The monomeric, two-coordinate complexes [(3,5-iPr2Ar*)Cr(L)] (6, L = THF; 7, L = PMe3; 3,5-iPr2Ar* = C6H1-2,6-(C6H-2,4,6-iPr3)2-3,5-iPr2) were obtained with use of the larger 3,5-Pri2-Ar* ligand, which prevents Cr-Cr bond formation. Their structures contain almost linearly coordinated CrI atoms, with high-spin 3d5 configurations. The addition of toluene to a mixture of (3,5-iPr2Ar*)CrCl and KC8 gave the unusual dinuclear benzyl complex [(3,5-iPr2Ar*)Cr(eta3:eta6-CH2Ph)Cr(Ar*-1-H-3,5-iPr2)] (8), in which a C-H bond from a toluene methyl group was activated. The electronic structures of 5-8 have been analyzed with the aid of DFT calculations.