Dinuclear copper(II) complexes with different bridging connectors

One novel triply-bridged dicopper(II) complex formulated as [Cu₂(dpa)₂(μ-Cl)(μ-OH)(μ-HCOO)]·(ClO₄) 1 and two terephthalate anions bridged 2,2′-bipyridine (2,2′-bpy) dicopper(II) complexes with formulae of [Cu₂(2,2′-bpy)₄(μ-terephthalate)]·(NO₃)₂2 and [Cu₂(2,2′-bpy)₄(μ-terephthalate)]·(terephthalate) 3, respectively, have been synthesized and characterized by infrared and electrospray mass spectra as well as X-ray single-crystal determination. In addition, thermal properties of all compounds have been studied.     

Harnessing polarisation transfer to indazole and imidazole through signal amplification by reversible exchange to improve their NMR detectability

The signal amplification by reversible exchange (SABRE) approach has been used to hyperpolarise the substrates indazole and imidazole in the presence of the co‐ligand acetonitrile through the action of the precataysts [IrCl(COD)(IMes)] and [IrCl(COD)(SIMes)]. ²H‐labelled forms of these catalysts were also examined. Our comparison of the two precatalysts [IrCl(COD)(IMes)] and [IrCl(COD)(SIMes)], coupled with ²H labelling of the N‐heterocyclic carbene and associated relaxation and polarisation field variation studies, demonstrates the critical and collective role these parameters play in controlling the efficiency of signal amplification by reversible exchange. Ultimately, with imidazole, a 700‐fold¹H signal gain per proton is produced at 400 MHz, whilst for indazole, a 90‐fold increase per proton is achieved. The co‐ligand acetonitrile proved to optimally exhibit a 190‐fold signal gain per proton in these measurements, with the associated studies revealing the importance the substrate plays in controlling this value. Copyright © 2017 The Authors. Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd.     

Practical synthesis of pinacolborane for one-pot synthesis of unsymmetrical biaryls via aromatic C-H borylation-cross-coupling sequence

A method for practical preparation of pinacolborane from borane-diethylaniline and pinacol was newly developed. Aromatic C-H borylation of arenes with pinacolborane or bis(pinacolato)diboron catalyzed by 1/2[Ir(OMe)(COD)]₂-(4,4′-di-tert-butyl-2,2′-bipyridine) at 25 °C in hexane to give arylboronic esters was directly followed by cross-coupling with aromatic bromides at 60 °C in the presence of PdCl₂(dppf) (3.0 mol %) and K₃PO₄ in DMF. This one-pot, two-step procedure provided a variety of unsymmetrical biaryls in high yields.     

Reactivity of allylphosphines with iridium complexes: Diallylphosphines as new bidentate ligands

Addition of four equivalents of t-butyldiallylphosphine 1a to a solution of one equivalent of [(COE)₂IrCl]₂ in CHCl₃ at low temperature produced two isomers of thecomplex [t-Bu(C₃H₅)PCH₂CH=CH)]IrHCl(COE)-[PtBu(C₃H₅)₂] ( 2a ), which evolve at 40°C to [t-Bu(C₃H₅)PCH₂CH=CH)]IrCl(C₈H₁₅)[PtBu(C₃H₅)₂] ( 3a ), by a hydride transfer from iridium to the cyclooctene (COE) ligand. It is reasonable that the unsaturation at the iridium center is fulfilled by interactions with the allyl moieties of the phosphine that are not metalated. This has been demonstrated by bubbling CO into a solution of 3a in CHCl₃ at room temperature to obtain the carbonyl complex [t-Bu(C₃H₅)-PCH₂CH=CH)]Ir(CO)Cl(C₈H₁₅)[PtBu(C₃H₅)₂] ( 4a ). Under the same conditions, the reaction of diisopropylamindiallylphosphine 1b and anisyldiallylphosphine 1c afforded a mixture of isomers 3b and 3c , respectively. These results show that diallylphosphines can be considered to be a new family of bidentate ligands. Finally, the reaction of these phosphines with [(COD)IrCl]₂ (COD = 1,5 cyclooctadiene) shows the formation of tetracoordinated iridium (I) complexes IrCl(COD)(PR3), which are thermally stable. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:253–259, 1998     

2,2′-Bis((di-tert-butylphosphino)methyl)-1,1′-biphenyl (ditbi): a bulky analogue of bisbi. The crystal structure of [Rh2Cl2(1,5-cod)2(μ-ditbi)]

Diphosphine 2,2′-bis(di-tert-butylphosphino)methyl)-1,1′-biphenyl (ditbi) is synthesised by the addition of to 2,2′-bis(bromomethyl)-1,1′-biphenyl, followed by deprotection with diethylamine. Treatment of [Rh₂Cl₂(1,5-cod)₂], with ditbi gives [Rh₂Cl₂(1,5-cod)₂(μ-ditbi)] (2) as confirmed by its X-ray crystal structure determination. Hydroformylation of 1-hexene using [Rh(acac)(CO)₂]/ditbi as catalyst gave n- and iso-heptanal in a ratio of 1:1.     

Efficient bimetallic titanium catalyst for carbonyl-ene reaction

A new family of achiral 3,3′,5,5′-tetrasubstituted-2,2′,6,6′-tetrahydroxy biphenyl ligand 4 was developed. The axial chirality of the ligand could be induced by the chelation of 2,2′,6,6′-tetrahydroxy groups with (R)-BINOL-Ti(OⁱPr)₂ to form an axially chiral bimetallic titanium catalyst 9. Compared with (R)-BINOL-Ti(OⁱPr)₂ catalyst, this novel catalyst 9 exhibited excellent activity and enantioselectivity for the carbonyl-ene reaction of methylstyrene and ethyl glyoxylate. 3,3′,5,5′-Tetrasubstituted groups showed a remarkable effect on both enantioselectivity and yield. With 9d prepared from 3,3′,5,5′-tetramethyl-2,2′,6,6′-tetrahydroxy biphenyl 4d as the catalyst, the best result, up to 97.6% ee and 99% yield, was obtained. Additionally, the bimetallic catalyst 9 also showed better catalytic capability than the corresponding monometallic catalyst.     

Synthesis,structure, redox property and ligand replacement reaction of ruthenium(II) complexes containing a terpyridyl ligand with a redox active moiety

Ruthenium(II) complexes bearing a redox-active tridentate ligand 4′-(2,5-dimethoxyphenyl)-2,2′:6′,2′′-terpyridine (tpyOMe), analogous to terpyridine, and 2,2′-bipyridine (bpy) were synthesized by the sequential replacement of Cl by CH₃CN and CO on the complex. The new ruthenium complexes were characterized by various methods including IR and NMR. The molecular structures of [Ru(tpyOMe)(bpy)(CH₃CN)]²⁺ and two kinds of [Ru(tpyOMe)(bpy)(CO)]²⁺ were determined by X-ray crystallography. The incorporation of monodentate ligands (Cl, CH₃CN and CO) regulated the energy levels of the MLCT transitions and the metal-centered redox potentials of the complexes. The kinetic data observed in this study indicates that the ligand replacement reaction of [Ru(tpyOMe)(bpy)Cl]⁺ to [Ru(tpyOMe)(bpy)(CH₃CN)]²⁺ proceeds by a solvent-assisted dissociation process.     

Conformational behaviour of dinuclear Rh(I) complexes of the open-chain tetrapyrrolic ligand 2,2′-bidipyrrin (H2BDP)

The reaction of 2,2′-bidipyrrins H₂BDP with the Rh^I complexes [Rh(COD)(μ-OMe)]₂ and [Rh(CO)₂(μ-Cl)]₂ yields the neutral species [{Rh(COD)}₂BDP] (7, 8) and [{Rh(CO)₂}₂BDP] (2, 9), respectively. Treatment of the COD complexes with carbon monoxide results in the exchange of all COD ligands against CO. Ligand exchange studies on the carbonyl complexes 2 and 9 with different phosphane donors reveal the regioselective exchange of one CO per metal ion. In most cases, the reaction is accompanied by a large conformational change of the tetrapyrrole from a syn to an anti conformation. This conformational change was resolved by a combination of NMR spectroscopy and X-ray diffraction studies.     

Synthesis and characterization of coordination polymers of a carboxylato cyclophane with metal [Zn(II) and Cd(II)]-2,2′-bipyridines

N,N′,N′′,N′′′-Tetrakis(3-carboxy-propionyl)-1,6,20,25-tetraaza-[6.1.6.1] paracyclophane, H₄cp has been complexed with metal (Zn(II) and Cd(II)) 2,2′-bipyridyls. The resulting complexes of the composition [{Zn(2,2′-bpy)}₂(cp)]_n·4H₂O 1 and [{Cd(2,2′-bpy)}₂(cp)]_n·5H₂O 2 (2,2′-bpy = 2,2′-bipyridine) have been characterized using spectroscopic (IR, solid state UV–Vis), elemental analysis and single-crystal X-ray diffraction measurements. In these complexes the cyclophane coordinates in different modes, and in complex 2, Cd(II) is hepta-coordinated. However, under harsh reaction conditions (using excess nitric acid and a longer reaction time) debranching of the cyclophane is observed in the reaction of Zn(2,2′-bpy)(NO₃)₂ with H₄cp, and a complex of the composition [Zn(2,2′-bpy)(Suc)]_n3 (suc = succinate) is isolated. Using non-covalent interactions, complexes 1 and 2 provide 3D supramolecular structures, whereas an infinite 1D chain structure is observed for complex 3. The thermal and photoluminescence properties of the complexes have also been studied.     

Entangled zinc-ditetrazolate frameworks involving in situ ligand synthesis and topological modulation by various secondary N-donor ligands

The introduction of various secondary N-donor ligands into an in situ ditetrazolate-ligand synthesis system of terephthalonitrile, NaN₃ and ZnCl₂ led to the formation of three new entangled frameworks Zn(pdtz)(4,4′-bipy)·3H₂O (1), [Zn(pdtz)(bpp)]₂·3H₂O (2) and Zn(pdtz)_0.5(N₃)(2,2′-bipy) (3) (4,4′-bipy=4,4′-bipyridine; bpp=1,3-bis(4-pyridyl)propane; 2,2′-bipy=2,2′-bipyridine; H₂pdtz=5,5′-1,4-phenylene-ditetrazole). The formation of pdtz²⁻ ligand involves the Sharpless [2+3] cycloaddition reaction between terephthalonitrile and NaN₃ in the presence of Zn²⁺ ion as a Lewis-acid catalyst under hydrothermal conditions. Compound 1 exhibits a fivefold interpenetrating 3D framework based on the diamondoid topology. Compound 2 displays a twofold parallel interpenetrating framework based on the wavelike individual network. Compound 3 possesses a 2D puckered network. These new Zn-ditetrazolate frameworks are highly dependent on the modulation of different secondary N-donor ligands. Their luminescent properties were investigated.     

Cationic rhodium(I) complexes containing 4,4′-disubstituted 2,2′-bipyridines: A systematic variation on electron density over the metal centre

A series of [Rh(COD)(X₂-bipy)]BF₄ complexes (COD = 1,5-cyclooctadiene; X₂-bipy = 4,4′-disubstituted 2,2′-bipyridines; X = OCH₃, CH₃, H, Cl or NO₂) has been prepared from [Rh(COD)Cl]₂. The complexes for X = OCH₃, Cl and NO₂ have not been described previously in the literature. All complexes have been characterised by elemental analysis, IR, ¹H NMR and UV-Vis spectrometry. This series of complexes presents a wide variation on electron density over the metal centre with virtually no variation on its steric environment which discloses interesting possibilities for catalytic and electro-catalytic studies. A preliminary evaluation of these complexes on the hydroformylation of camphene and β-pinene showed that under the rather drastic conditions employed the complexes acted as a precursor for [Rh(CO)₃H], which accounts for most of the catalytic activity.     

Synthesis and characterization of monomeric siloxo palladium(II) complexes: crystal structure of [Pd(tmeda)(C6F5)(OSiPh3)]

Mononuclear palladium-hydroxo complexes of the type [Pd(N-N)(C₆F₅)(OH)] [(N-N)=2,2^′-bipyridine (bipy), 4,4^′-dimethyl-2,2^′-bipyridine (Me₂bipy), or N,N,N^′,N^′-tetramethylethylenediamine (tmeda)] react with silanols HOSiR₃ in toluene giving the corresponding siloxo complexes [Pd(N-N)(C₆F₅)(OSiR₃)]. The X-ray crystal structure of [Pd(tmeda)(C₆F₅)(OSiPh₃)] has been determined. In one of the two molecules in the asymmetric unit there is an intramolecular interaction by phenyl-pentafluorophenyl π-stacking.     

New optically active organoantimony (BINASb) and bismuth (BINABi) compounds comprising a 1,1′-binaphthyl core: synthesis and their use in transition metal-catalyzed asymmetric hydrosilylation of ketones

Racemic 2,2′-bis[diarylstibano]-1,1′-binaphthyls [(±)-BINASbs] and 2,2′-bis[di(p-tolyl)bismuthano]-1,1′-binaphthyl [(±)-BINABi], which are the antimony and bismuth congeners of BINAP, have been prepared from 2,2′-dibromo-1,1′-binaphthyl (DBBN) via 2,2′-dilithio-1,1′-binaphthyl intermediate by treatment with the appropriate metal halides [(p-Tol)₂SbBr, Ph₂SbBr and (p-Tol)₂BiCl]. The optical resolution of the (±)-BINASbs could be achieved via the separation of a mixture of the diastereomeric Pd-complexes derived from the reaction of (±)-BINASbs with di-μ-chlorobis{(S)-2-[1-(dimethylamino)-ethyl]phenyl-C¹,N}dipalladium(II). Optically active (R)-BINASb and (R)-BINABi could be also obtained from optically active (R)-DBBN by the same procedure. The enantiopure BINASbs have been shown to be effective chiral ligands for the rhodium-catalyzed asymmetric hydrosilylation of ketones.     

Hydrothermal syntheses, crystal structures and properties of 0-D, 1-D and 2-D organic-inorganic hybrid borotungstates constructed from Keggin-type heteropolyanion [α-BW12O40] and transition-metal complexes

Three novel organic-inorganic hybrid borotungstates {[Ni(phen)₂(H₂O)]₂H(α-BW₁₂O₄₀)}·4H₂O (1), [Cu^I(2,2'-bipy)(4,4′-bipy)_0.5]₂{[Cu^I(2,2′-bipy)]₂Cu^I(4,4′-bipy)₂(α-BW₁₂O₄₀)} (2) and {[Cu^I(4,4′-bipy)]₃H₂(α-BW₁₂O₄₀)}·3.5H₂O (3) (phen=1,10-phenanthroline, 2,2′-bipy=2,2′-bipyridine, 4,4′-bipy=4,4′-bipyridine) have been hydrothermally synthesized and structurally characterized by elemental analyses, IR, UV spectra, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), single-crystal X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and photoluminescence. The structural analysis reveals that 1 consists of a 0-D bisupporting polyoxometalate cluster where two [Ni(phen)₂(H₂O)]²⁺ cations are grafted on the polyoxoanion [α-BW₁₂O₄₀]^5- through two terminal oxygen atoms, 2 shows a 1-D infinite chain constructed from [α-BW₁₂O₄₀]^5- polyoxoanions and {[Cu^I(2,2′-bipy)]₂Cu^I(4,4′-bipy)₂}³⁺ cations by means of alternating fashion, and 3 displays an unprecedented 2D extended structure built by [α-BW₁₂O₄₀]^5- polyoxoanions and -Cu^I-4,4′-bipy- linear chains, in which each [α-BW₁₂O₄₀]^5- polyoxoanion acts as a tetradentate inorganic ligand and provides three terminal oxygen atom and one two-bridging oxygen atom. The presence of Ni^II and W^VI in 1, Cu^I ions and W^VI in 2 and 3 are identified by XPS spectra. The photoluminescence of 2 and 3 are also investigated.     

Hydrothermal syntheses, structures and characterizations of three one-dimensional polyoxomolybdates with 4,4′-dimethylenebiphenyl diphosphonic acid as bridge

Three heterometallic 1-D polymers, [{Ni(1,10-phen)₂(H₂O)}₂ {(Mo₅O₁₅)(4,4′-dbp)}·(5.75H₂O)] (4,4′-dbp=O₃PCH₂C₆H₄C₆H₄CH₂PO₃) (1), [{Co(1,10-phen)₂(H₂O)}₂ {(Mo₅O₁₅)(4,4′-dbp)}·(5.5H₂O)] (2) and [{Ni(2,2′-bpy)₃}{Ni(2,2′-bpy)₂(H₂O)} {(Mo₅O₁₅)(4,4′-dbp)}·(4.75H₂O)] (3), have been synthesized under hydrothermal conditions. Their structures were determined by single crystal X-ray diffraction. The 1-D chains is constructed of [Mo₅O₁₅(4,4′-dbp)]⁴⁻ units, which are further decorated and charge compensated by [M(1,10-phen)₂] (M=Ni, Co) or [Ni(2,2′-bpy)₂] subunits. The thermogravimetric analyses and magnetic properties of 1 and 2 were studied.     

Assembly and structures of five new Cu(II) complexes based on the V-shaped building block [Cu(dbsf)]

Five new copper(II) complexes [Cu(dbsf)(H₂O)]_n · 0.5n(i-C₃H₇OH) (1), [Cu(dbsf)(4,4′-bpy)_0.5]_n · nH₂O (2), [Cu(dbsf)(2,2′-bpy)(H₂O)]₂ · (n-C₃H₇OH) · 0.5H₂O (3), [Cu(dbsf)(phen)(H₂O)]₂ · 1.5H₂O (4) and [Cu(dbsf)(2,2′-bpy)(H₂O)]_n · n(i-C₃H₇OH) (5) (H₂dbsf = 4,4′-dicarboxybiphenyl sulfone, 4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, i-C₃H₇OH = isopropanol, n-C₃H₇OH = n-propanol) have been synthesized under hydro/solvothermal conditions. All of the complexes are assembled from V-shaped building blocks, [Cu(dbsf)]. Complex 1 is composed of 1D double-chains. In complex 2, dbsf²⁻ ligands and 4,4′-bpy ligands connect Cu(II) ions into catenane-like 2D layers. These catenane-like 2D layers stack in an ABAB fashion to form a 3D supramolecular network. Complexes 3 and 4 are 0D dimers, in which two [Cu(dbsf)] units encircle to form dimetal macrocyclic molecules. However, in complex 5, the V-shaped building blocks [Cu(dbsf)] are joined head-to-tail, resulting in the formation of infinite tooth-like chains. The different structures of complexes 3 and 5 may be attributed to the different solvent molecules included.     

Synthese,Struktur und Eigenschaften der Komplexe [(Me2PhP)3Cl2Re≡N‐IrCl2(C5Me5)], [(Me2PhP)3Cl2Re≡N‐IrCl(COD)], [PPh4][O3Os≡N‐IrCl2(C5Me5)] und [PPh4][O3Os≡N‐IrCl(COD)] mit Nitridobrücken Re≡N‐Ir und Os≡N‐Ir

Synthesis and Crystal Structures of the Complexes [(Me₂PhP)₃Cl₂Re≡N‐IrCl₂(C₅Me₅)], [(Me₂PhP)₃Cl₂Re≡N‐IrCl(COD)], [PPh₄][O₃Os≡N‐IrCl₂(C₅Me₅)], and [PPh₄][O₃Os≡N‐IrCl(COD)] with Nitrido bridges Re≡N‐Ir and Os≡N‐Ir The heteronuclear complexes [(Me₂PhP)₃Cl₂Re≡N‐IrCl₂(C₅Me₅)] ( 1 ), [(Me₂PhP)₃Cl₂Re≡N‐IrCl(COD)] ( 2 ), [PPh₄][O₃Os≡N‐IrCl₂(C₅Me₅)] ( 3 ) and [PPh₄][O₃Os≡N‐IrCl(COD)] ( 4 ) were obtained by the reaction of the nitrido complexes [ReNCl₂(PMe₂Ph)₃] and [OsO₃N]^— with the iridium compounds [IrCl₂(C₅Me₅)]₂ and [IrCl(COD)]₂ in benzonitrile. 1 forms red crystals with the composition 1 ·C₆H₅CN in the monoclinic space group P2₁/c and a = 1264.7(2); b = 1945.3(2); c = 1835.4(1) pm, β = 90.35(1)°, Z = 4. The complex fragment [IrCl₂(C₅Me₅)] in the dinuclear complex is connected by an asymmetric nitrido bridge Re≡N‐Ir to the nitrido complex [ReNCl₂(PMe₂Ph)₃]. The nitrido bridge is characterized by a Re‐N‐Ir bond angle of 179.4(2)° and distances Re‐N = 170.9(4) pm and Ir‐N = 203.3(4) pm. 2 forms brownish red, triclinic crystals with the space group P1¯ and a = 1076.6(2), b = 1373.2(2), c = 1452.4(1) pm, α = 107.513(8), β = 101.843(9), γ = 110.04(1)°, Z = 2. The nitrido bridge to the complex fragment [IrCl(COD)] has a Re‐N‐Ir bond angle of 173, 8(4)° and distances Re‐N = 170, 4(8) pm and Ir‐N = 196, 2(8) pm. 3 crystallizes as monoclinic red crystals in the space group P2₁/n and a = 1449.9(2), b = 906.74(4), c = 2628.9(5) pm, β = 103.50(1)°, Z = 4. The nitrido bridge Os≡N‐Ir is slightly bent (Os‐N‐Ir = 165.0(3)°). The distances are Os‐N = 168.3(5) pm and Ir‐N = 201.9(5) pm. 4 forms dark brown, orthorhombic crystals with the space group P2₁2₁2₁ and a = 704.35(2), b = 1228.17(6), c = 3442.0(4) pm, Z = 4. The distances in the slightly bent nitrido bridge (Os‐N‐Ir = 161.8(4)°) are Os‐N = 169.3(7) pm und Ir‐N = 197.8(7) pm.     

Synthesis and characterization of new epoxy and cyanate ester resins

New epoxide and cyanate ester resins with an aromatic ester backbone namely 1,3-[di-(4-glycidyloxy diphenyl-2,2^′-propane)]-isophthalate (DGDPI) and 1,4-[di-(4-cyanato diphenyl-2,2^′-propane)]-terephthalate (DCDPT) were synthesized and the intermediates were characterized by IR, 1H-/¹³C-NMR spectroscopic methods. The cured products from DGDPI and DHDPI exhibited higher T_g compared with standard epoxy system. The increase in the T_g may be due to the cyanate ester and rigid aromatic backbones present in the curing system.     

A novel synthesis of spiro[(2,2-dimethyl-[1,3]-dioxane)-5,2′-(2′,3′-dihydroindole)] using SRN1 reaction conditions

A concise synthesis of the spiro[(2,2-dimethyl-[1,3]-dioxane)-5,2′-(2′,3′-dihydroindole)] nucleus from substituted benzyl chlorides and 5-(hydroxymethyl)-2,2-dimethyl-5-nitro-1,3-dioxane 5 as starting materials is reported. The nitro intermediates 6 and 7 were prepared under S_RN1 reaction conditions.     

Enantioselective catalytic allylation of arylmethylketones using tetraallyltin and tin(IV) chloride mixtures

Reaction of SnCl₄ with Sn(CH₂CHCH₂)₄ in the presence of water and monothiobinaphthol [2,2′-C₂₀H₁₂(OH)(SH)] allows the formation of a selective catalyst for the allylation of ketones (up to 94% e.e.).