Effects of solvent and base on the palladium-catalyzed amination: PdCl2(Ph3P)2/Ph3P-catalyzed selective arylation of primary anilines with aryl bromides

A readily accessible catalytic system, PdCl₂(Ph₃P)₂/Ph₃P, was developed for the selective arylation of primary anilines with aryl bromides. The strong influence of solvents and bases on the catalytic activity was observed. In refluxing o-xylene, triphenylphosphine shows high efficiency for Pd-catalyzed intermolecular amination reactions. By changing the bases, mono- and diarylation of primary amines could be selectively achieved in high yields. Moreover, the catalytic system showed good toleration for the steric hindrance of anilines. A series of N,N,N′,N′-tetraaryl-1,1′-biphenyl-4,4′-diamines, important intermediates of OLED hole transport materials, were synthesized facilely via coupling reactions between 4,4′-diaminobiphenyls and aryl bromides.     

Pd(OAc)2/DABCO-catalyzed Suzuki-Miyaura cross-coupling reaction in DMF

The scope and limitations of the Pd(OAc)₂/DABCO (1,4-diaza-bicyclo[2.2.2]octane)-catalyzed Suzuki-Miyaura cross-coupling reactions have been demonstrated. The results showed that the effect of solvent had a fundamental influence on the reaction. In the presence of Pd(OAc)₂ and DABCO, both aryl bromides and aryl chlorides all worked well with arylboronic acids to form biaryls, heteroaryl-aryls, and biheteroaryls in moderate to excellent yields using DMF as the solvent. Additionally, the reactions of aryl bromides were conducted under relatively mild conditions.     

Pd2(dba)3/Xantphos-catalyzed cross-coupling of thiols and aryl bromides/triflates

The cross-coupling of aliphatic and aromatic thiols and aryl bromides/triflates mediated by a Pd₂(dba)₃/Xantphos catalytic system in refluxing xylene (140 °C) affords the corresponding aryl thioethers in good to excellent yields.     

[RuCl3(H2O)n]-catalyzed direct arylations

Catalytic amounts of economically attractive [RuCl₃(H₂O)_n] allow for direct arylations via C-H bond functionalization with aryl bromides under phosphine ligand-free reaction conditions. Thereby, a variety of functionalized (hetero)aryl bromides, bearing either electron-withdrawing or electron-releasing substituents, can be employed for direct arylations of pyridine, oxazoline, pyrazole, or ketimine derivatives as pronucleophiles.     

Microwave-assisted Pd(OH)2-catalyzed direct C−H arylation of free-(NH2) adenines with aryl halides

A direct C−H arylation of free-(NH₂) adenines using Pd(OH)₂/C (Pearlman’s catalyst) and stoichiometric amount of copper iodide under ligandless microwave activation is described. This new protocol proved to be highly effective to synthesize a variety of 8-aryladenine derivatives 3 without prior protection of the amino substituent. The arylation reaction takes place rapidly within few minutes and allows the coupling to proceed regioselectively at the 8-position with a wide range of aryl halides including aryl iodides, bromides and the less reactive aryl chlorides.     

Microwave-enhanced and ligand-free copper-catalyzed cyanation of aryl halides with K4[Fe(CN)6] in water

Copper-catalyzed cyanation of aryl halides was improved to be more economical and environmentally friendly by using water as the solvent and ligand-free Cu(OAc)₂·H₂O as the catalyst under microwave heating. The suggested methodology was applicable to a wide range of substrates including aryl iodides and activated aryl bromides.     

A new and unusual isomerism in [Fe(CO)2 {P(OR)3}2 (SO2)] complexes (R = aryl)

[Fe(CO)₂ {P(OR)₃}₂ (SO₂)] complexes (R = aryl) exist in solution as equilibrium mixtures of two isomers; both have been shown by X-ray diffraction studies (where R = Ph or o-MeC₆H₄) to have planar coordination about SO₂ and trigonal bipyramidal coordination about Fe, but in one isomer (R = Ph) the equatorial plane is occupied by SO₂ and two CO ligands whilst in the other one (R = o-MeC₆H₄) it is occupied by the SO₂ and two P ligands.     

Efficient cyanation of aryl bromides with K4[Fe(CN)6] catalyzed by a palladium-indolylphosphine complex

This study describes a general palladium-catalyzed cyanation of aryl bromides using K₄[Fe(CN)₆] as the cyanide surrogate. The reactions can be successfully conducted under mild reaction conditions (at 50 °C) in mixed solvents (water/MeCN = 1:1) without any surfactant additives, and afford the desired aryl nitriles in good-to-excellent yields. Particularly noteworthy is that this system allows the mildest reaction temperature reported so far for palladium-catalyzed cyanation of aryl bromides with K₄[Fe(CN)₆] source in general. Common functional groups, including keto, aldehyde, free amine, and heterocyclic substrates are compatible under this system. Interestingly, the phosphine ligands bearing -PCy₂ moiety, which usually show excellent activity in aryl halide couplings, are found less effective than the corresponding ligands with -PPh₂ group.     

Crystal structures of phosphomolybdyl salts: Pb(MoO2)2(PO4)2 and Ba(MoO2)2(PO4)2

Crystal structures of Pb(MoO₂)₂(PO₄)₂ and Ba(MoO₂)₂(PO₄)₂ were determined. Both compounds contain the molybdyl group MoO₂. The monoclinic unit-cell parameters are a = 6.353(7), b = 12.289(4), c = 11.800 Å, β = 92°56(6), and Z = 4 for the lead salt and a = 6.383(8), b = 7.142(7), c = 9.953(8) Å, β = 95°46(8), and Z = 2 for the barium salt. $\text{P2}{}_1\text{c}$ is the common space group. The R values are respectively R = 0.027 and R = 0.031 for 1964 and 1714 independent reflections. The frameworks built up by a three-dimensional network of monophosphate PO₄ and molybdyl MoO₂ groups are similar, characterized mainly by corner-sharing PO₄ and MoO₆ polyhedra. Two oxygen atoms of each MoO₆ group are bonded to the molybdenum atom only as in other molybdyl salts.     

Palladium-catalyzed cyanation of aryl halides using K4[Fe(CN)6] as cyanide source, water as solvent, and microwave heating

A methodology for the cyanation of aryl iodides and activated aryl bromides is reported using water as the solvent and K₄[Fe(CN)₆] as the cyanide source. Reactions are complete within 20 min.     

Synthesis and characterisation of HRuRh3(CO)12. Crystal structures of HRuRh3(CO)12, HRuRh3(CO)10(PPh3)2 and HRuCo3(CO)10(PPh3)2

A new ruthenium-rhodium mixed-metal cluster HRuRh₃(CO)₁₂ and its derivatives HRuRh₃(CO)₁₀(PPh₃)₂ and HRuCo₃(CO)₁₀(PPh₃)₂ have been synthesized and characterized. The following crystal and molecular structures are reported: HRuRh₃(CO)₁₂: monoclinic, space group P2₁/c, a 9.230(4), b 11.790(5), c 17.124(9) Å, β 91.29(4)°, Z = 4; HRuRh₃(CO)₁₀(PPh₃)₂·C₆H₁₄: triclinic, space group P$\text{1}$, a 11.777(2), b 14.079(2), c 17.010(2) Å, α 86.99(1), β 76.91(1), γ 72.49(1)°, Z = 2; HRuCo₃(CO)₁₀(PPh₃)₂·CH₂Cl₂: triclinic, space group P$\text{1}$, a 11.577(7), b 13.729(7), c 16.777(10) Å, α 81.39(4), β 77.84(5), γ 65.56°, Z = 2. The reaction between Rh(CO)₄^? and (Ru(CO)₃Cl₂)₂ tetrahydrofuran followed by acid treatment yields HRuRh₃(CO)₁₂ in high yield. Its structural analysis was complicated by a 80–20% packing disorder. More detailed structural data were obtained from the fully ordered structure of HRuRh₃(CO)₁₀(PPh₃)₂, which is closely related to HRuCo₃(CO)₁₀(PPh₃)₂ and HFeCo₃(CO)₁₀(PPh₃)₂. The phosphines are axially coordinated.     

[PdCl2{8-(di-tert-butylphosphinooxy)quinoline)}]: a highly efficient catalyst for Suzuki-Miyaura reaction

The complex [PdCl₂(P-N)] containing the basic and sterically demanding 8-(di-tert-butylphosphinooxy)quinoline ligand (P-N) is a highly efficient catalyst for the coupling of phenylboronic acid with aryl bromides or aryl chlorides. The influence of solvent and base has been investigated, the highest rates being observed at 110 °C in toluene with K₂CO₃ as the base. With aryl bromides the reaction rates are almost independent on the electronic properties of the para aryl substituents, on the contrary, reduced reaction rates are observed when bulky substituents are present on the substrate. Nevertheless the coupling of 2-bromo-1,3,5-trimethylbenzene with phenylboronic acid can be carried out to completion in 2 h using a catalyst loading of 0.02 mol %. Under optimized reaction conditions, turnover frequencies as high as 1900 h⁻¹ can be obtained in the coupling of 4-chloroacetophenone with phenylboronic acid; lower reaction rates are obtained with substrates bearing EDG substituents on the aryl group.     

One pot Pd(OAc)2-catalysed 2,5-diarylation of imidazoles derivatives

The regioselective 2- or 5-arylation of imidazole derivatives with aryl halides using palladium catalysts has been described in recent years; whereas the arylation at both C2 and C5 carbons of imidazoles in high yields has not been performed. We found conditions allowing the access to these 2,5-diarylimidazoles via a one pot reaction. The choice of the base was found to be crucial to obtain these products in high yields. Using CsOAc as the base, DMA as the solvent and only 2 mol % of the phosphine-free Pd(OAc)₂ the catalyst, the target 2,5-diarylated imidazoles were obtained in moderate to good yields with a wide variety of aryl bromides. Substituents such as fluoro, trifluoromethyl, formyl, acetyl, propionyl, ester, nitro or nitrile on the aryl bromide were tolerated. Sterically congested aryl bromides or heteroaryl bromides can also be employed. Surprisingly the nature of the substituent at position 1 on the imidazole derivative exhibits a huge influence on the reaction.     

Synthesis, characterization, and X-ray crystal structure of the octabromodiosmate(III) salt [(C5Me4H)2OsBr]2[Os2Br8] and its conversion to [(C5Me4H)2OsBr][Os2HBr4(cod)2]

Treatment of hexabromoosmic acid, H₂OsBr₆, with 4 equiv. of tetramethylcyclopentadiene (C₅Me₄H₂) in tert-butanol at reflux for 8 h affords the unusual salt [(C₅Me₄H)₂OsBr]₂[Os₂Br₈], 1, which is the bis(tetramethylcyclopentadienyl)bromoosmocinium(IV) salt of the octabromodiosmate(III) dianion. The brown color of the salt suggests that the anion adopts an eclipsed conformation (D_4h symmetry) and this conclusion has been confirmed by a single-crystal X-ray diffraction experiment. The X-ray crystal structure indicates that the osmium atoms in the anion are disordered over two sites. The bromine atoms show no evidence of disorder and are disposed in a quasi-cubic arrangement; the two Os-Os vectors are almost exactly orthogonal to each other and each vector points toward a different pair of opposite square faces of the Br₈ cube. The Os-Os bond distances are 2.219(5) and 2.229(1) Å; the average Os-Br distance in the anion is 2.417(2) Å. Treatment of [(C₅Me₄H)₂OsBr]₂[Os₂Br₈] with excess 1,5-cyclooctadiene in ethanol at gentle reflux for 3 h affords [(C₅Me₄H)₂OsBr][Os₂HBr₄(cod)₂], 2. An X-ray crystallographic study was carried out on a sample in which the cation was a mixture of [(C₅Me₄H)₂OsBr⁺] and [(C₅Me₄H)₂OsH⁺]. The results demonstrate that the anion adopts a confacial bioctahedral structure in which the hydride ligand and two bromides bridge between the two osmium centers. The CC bonds of the cod ligands are trans to the bridging bromide groups. The Os-Os bond distance in the anion is 2.874(1) Å. The average Os-Br distance is 2.596(2) Å for the bridging bromides and 2.565(2) Å for the terminal bromides. Compound 2 is the first example of an anionic diosmium complex containing a bridging hydride. The reaction of 1 with cod also results in the formation of bis(tetramethylcyclopentadienyl)osmocene, (C₅Me₄H)₂Os, 3, which has been isolated and characterized. Treatment of (C₅Me₄H)₂Os with 1.0 equiv. of HBF₄ · Et₂O affords the osmocinium salt [(C₅Me₄H)₂OsH][BF₄].     

Specific heat measurements on the magnetic layer compounds(BA)2Cu(Ox)2 and (CHA)2Cu(Ox)2·H2O

Specific heat data on (BA)₂Cu(Ox)₂ and (CHA)₂Cu(Ox)₂·H₂O below 1 K are reported (BA = C₆H₅ CH₂NH₃⁺, CHA = C₆H₃⁺, Ox = C₂O₄²). The magnetic contributions have the form of broad maxima, occurring near 0.15. A λ-type anomaly is observed for (BA)₂Cu(Ox)₂ at T_c = 0.116(3) K. For (CHA)₂Cu(Ox)₂·H₂O no such ordering is seen.(BA)₂Cu(Ox)₂ appears to be a quadratic S = 1/2 Heisenberg antiferromagnet with J/k = ?0.145 (3) K. The compound (CHA)₂Cu(Ox)₂·H₂O shows a behaviour that is in between 1-D and 2-D S = 1/2 Heisenberg antiferromagnetism.     

Cluster condensation reactions. The synthesis and crystal and molecular structure of Os6(CO)14(μ2-PPh2)2(μ3-S)3(μ4-S)

Thermal degradation of the cluster compound Os₃(CO)₈(PPh₂H)(μ₃-S)₂ (I) at 125°C leads to decarbonylation and formation of the new ligand bridged hexanuclear cluster Os₆(CO)₁₄(μ-PPh₂)₂(μ₃-S)₃(μ₄-S) (II) in 11% yield. Space Group: P$\text{1}$, No. 2, a 10.427(5), b 13.552(3), c 17.919(3) Å, α 84.87(2), β 75.41(3), γ 78.43(3)°, V 2399(2) ųZ = 2, _?calc 2.82 g cm^?3. The structure was solved by the heavy atom method and refined (3223 reflections) to the final residuals R = 0.042 and R_w = 0.036. The molecule consists of two sulfido bridged open triosmium clusters which are linked by a bridging sulfido ligand and a bridging diphenylphosphino ligand.     

An efficient and simple protocol for a PdCl2-ligandless and additive-free Suzuki coupling reaction of aryl bromides

A highly efficient, convenient, and environmentally friendly protocol was developed for the PdCl₂-catalyzed ligandless and additive-free Suzuki reaction of aryl bromides with arylboronic acids in water/ethanol.     

Synthesis,Characterization, and DNA Binding Properties of Dinuclear Copper（Ⅱ） Complex [Cu2（TATP）2（L-Leu）2（CIO4）2]2·2H2O

A dinuclear copper（Ⅱ） complex[Cu2（TATP）2（L-Leu）2（CIO4）2]2·2H2Owas synthesized and characterized, where, TATP=1,4,8,9-tetraazatriphenylene, and L-Leu=L-leucinate. The complex was crystallized in the triclinic space group P1, with two independent molecules in a unit cell. Two Cu（Ⅱ） ions in each complex [Cu2（TATP）2（L-Leu）2（CIO4）2] molecule were found to be in different coordination geometries, i.e., Cu2 or Cu4 of a distorted square-pyramidal geometry coordinated with two nitrogens of TATP, the amino nitrogen and one carboxylate oxygen of L-Leu and one oxygen of perchlorate, and Cul or Cu3 with an octahedral geometry coordinated with the above stated similar coordinated atoms, and another carboxylate oxygen of L-Leu coordinating to Cu2 or Cu4. The complex can interact with CT-DNA by an intercalative mode and cleave pBR322 DNA in the presence of ascorbate.     

New open-framework in the uranyl vanadates A3(UO2)7(VO4)5O (A=Li, Ag) with intergrowth structure between A(UO2)4(VO4)3 and A2(UO2)3(VO4)2O

New uranyl vanadates A₃(UO₂)₇(VO₄)₅O (M=Li (1), Na (2), Ag (3)) have been synthesized by solid-state reaction and their structures determined from single-crystal X-ray diffraction data for 1 and 3. The tetragonal structure results of an alternation of two types of sheets denoted S for _∞²[UO₂(VO₄)₂]⁴⁻ and D for _∞²[(UO₂)₂(VO₄)₃]⁵⁻ built from UO₆ square bipyramids and connected through VO₄ tetrahedra to _∞¹[U(3)O₅-U(4)O₅]⁸⁻ infinite chains of edge-shared U(3)O₇ and U(4)O₇ pentagonal bipyramids alternatively parallel to a- and b-axis to construct a three-dimensional uranyl vanadate arrangement. It is noticeable that similar _∞[UO₅]⁴⁻ chains are connected only by S-type sheets in A₂(UO₂)₃(VO₄)₂O and by D-type sheets in A(UO₂)₄(VO₄)₃, thus A₃(UO₂)₇(VO₄)₅O appears as an intergrowth structure between the two previously reported series. The mobility of the monovalent ion in the mutually perpendicular channels created in the three-dimensional arrangement is correlated to the occupation rate of the sites and by the geometry of the different sites occupied by either Na, Ag or Li. Crystallographic data: 293 K, Bruker X8-APEX2 X-ray diffractometer equipped with a 4 K CCD detector, MoKα, λ=0.71073 Å, tetragonal symmetry, space group P4¯m2, Z=1, full-matrix least-squares refinement on the basis of F²; 1,a=7.2794(9) Å, c=14.514(4) Å, R1=0.021 and wR2=0.048 for 62 parameters with 782 independent reflections with I?2σ(I); 3, a=7.2373(3) Å, c=14.7973(15) Å, R1=0.041 and wR2=0.085 for 60 parameters with 1066 independent reflections with I?2σ(I).     

Syntheses and structural studies on two cycloruthenapentadienyl complexes: [(CO)3RuC4(CH2OH)4]Ru(CO)3·H2O and [(CO)3RuC4(CH2CH2OH)2(C2H5)2]Ru(CO)3

Syntheses and single-crystal X-ray diffraction studies have been completed on two cycloruthenapentadienyl (CO)₆Ru₂L₂ derivatives, with L = CH₂OHC = CCH₂OH and C₂H₅C=CCH₂CH₂OH respectively. Crystal data are as follows: for [(CO)₃RuC₄(CH₂OH)₄]Ru(CO)₃·H₂O, P2₁/c, a 13.72(1), b 9.501(4), c 14.86(1) Å, β 101.10(6)°, R_w = 0.052 for 1911 reflections; for [(CO)₃RuC₄(CH₂CH₂OH)₂(C₂H₅)₂]Ru(CO)₃, P2₁/c, a 9.191(3), b 16.732(4), c 14.903(3) Å, β 113.61(4)°, R_w = 0.042 for 2865 reflections. Both compounds are built up from binuclear units, each unit being regarded as a Ru(CO)₃ fragment π-bonded to a cycloruthenapentadienyl ring. The molecular parameters are compared with those of known cyclometallapentadienyl complexes of transition metals. The presence of a semi-bridging CO group is discussed.