Showing papers in "Journal of The Chemical Society-dalton Transactions in 1994"
TL;DR: In this paper, the 1-ethyl-3-methyl-imidazolium cation, [emim]+, not only forms strong hydrogen bonds (using all three ring protons H2, H4 and H5) with halide ions in polar molecular solvents (e.g. ethanenitrile) and ionic liquids, but that it exists in a quasi-molecular state, [EMim]X, in non-polar liquid, showing a conventional aromatic stacking phenomenon.
Abstract: Multinuclear NMR spectroscopy and conductivity measurements showed that the 1-ethyl-3-methyl-imidazolium cation, [emim]+, not only forms strong hydrogen bonds (using all three ring protons H2, H4 and H5) with halide ions in polar molecular solvents (e.g. ethanenitrile) and ionic liquids, but that it exists in a quasi-molecular state, [emim]X, in non-polar solvents (e.g. trichloro- and dichloro-methane), showing a conventional aromatic stacking phenomenon.
267 citations
TL;DR: The dianionic rhenium(I) hydroxo complex [ReBr3(CO)3]2 has been synthesized and characterized as discussed by the authors, and it is stable in aqueous solution even when exposed to air for weeks.
Abstract: The dianionic rhenium(I) complex [ReBr3(CO)3]2– has been synthesized and characterized. This complex is an important starting material for compounds containing the fac-Re(CO)3 moiety since the three bromide ligands are very weakly bound. Particularly in co-ordinating solvents, the bromides are substituted by solvent molecules thus generating the strong 12e– Lewis acid [Re(H2O)3(CO)3]+2. This formula was confirmed, particularly in water, by IR spectroscopic methods. Complex 2 is stable in aqueous solution even when exposed to air for weeks. It has been titrated by NaOH solutions. The change in pH was detected potentiometrically and found to occur very slowly, indicating a reaction other than protonation deprotonation. Depending on the rate of titration and the total concentration of OH–, the two rhenium(I) hydroxo complexes [NEt4][Re3(µ3-OH)(µ-OH)3(CO)9] and [NEt4][Re2(µ-OH)3(CO)6] were isolated in good yield and structurally characterized. The former crystallizes in the orthorhombic space group Pnma with a= 10.752(7), b= 13.783(8) and c= 18.254(12)A. The skeletal framework is that of a cube lacking the Re(CO)3 unit in one corner. The latter crystallizes in the orthorhombic space group P2mm with Z= 1, a= 6.551(2), b= 7.413(2) and c= 12.084(2)A. The two Re(CO)3 moieties are bridged by three OH– ligands which create a mirror plane. A second mirror plane is perpendicular to it along the Re-Re axis.
201 citations
TL;DR: In this article, metal-free phthalocyanines and metal phthalochemicals carrying eight alkylthio-groups on peripheral positions have been synthesized from 4,5-bis(alkylthio)phthalonitrile and 1,8-diazabicyclo[5.0]undec-7-ene (dbu) or the corresponding anhydrous metal salt [NiCl2, CuCl, CoCl2 or Zn(O2CMe)2].
Abstract: Metal-free phthalocyanines and metal phthalocyaninates (M = Ni, Cu, Co or Zn) carrying eight alkylthio-groups on peripheral positions have been synthesised from 4,5-bis(alkylthio)phthalonitrile and 1,8-diazabicyclo[5.4.0]undec-7-ene (dbu) or the corresponding anhydrous metal salt [NiCl2, CuCl, CoCl2 or Zn(O2CMe)2]. The resulting compounds reacted with silver(I) or palladium(II) salts to form complexes with a phthalocyanine:metal ratio of 1 : 4. Spectrophotochemical investigation of these reactions revealed that complexation with AgI results in aggregation, while the addition of PdII destroys the aggregation and yields a new Q band at 720 nm.
145 citations
TL;DR: In this paper, photoelectrochemical cells based on colloidal films of titanium dioxide and zinc oxide ceramic electrodes sensitized by a bis(2,9-diphenyl-1,10-phenanthroline)copper(I) complex modified at the para positions with NaO2C groups, were investigated in an aqueous medium using hydroquinone as electron donor.
Abstract: Photoelectrochemical cells based on colloidal films of titanium dioxide and zinc oxide ceramic electrodes sensitized by a bis(2,9-diphenyl-1,10-phenanthroline)copper(I) complex modified at the para positions with NaO2C groups, were investigated in an aqueous medium using hydroquinone as electron donor. The sensitizing effect is greater with the films due to the enhanced geometric area projection. The photocurrent-action spectrum obtained with this complex covers almost the whole of the solar visible region. The quantum efficiency was found to depend on the degree of surface coverage by the complex. In a solar-cell arrangement the open-circuit photovoltage was 0.6 V with a small short-circuit photocurrent of ca. 0.6 mA cm–2 in iodide-containing propylene carbonate.
144 citations
TL;DR: In this article, three new dinuclear cobalt(II) complexes [Co2(H2O)8(bipym)][NO3]41, [Co 2(H 2O]8(Bipym)]]-SO4]2·2H2 O 2 and [Co3(bistym)3(NCS)4]4]3(Bistym = 2,2′-bipyrimidine) have been synthesized and their crystal structures determined by X-ray diffraction methods.
Abstract: Three new dinuclear cobalt(II) complexes [Co2(H2O)8(bipym)][NO3]41, [Co2(H2O)8(bipym)]-[SO4]2·2H2O 2 and [Co2(bipym)3(NCS)4]3(bipym = 2,2′-bipyrimidine) have been synthesised and their crystal structures determined by X-ray diffraction methods. Crystals of 1 and 3 are triclinic, space group P, Z= 1 with a= 7.511(1), b= 8.844(2), c= 9.514(1)A, α= 79.67(1), β= 88.54(1) and γ= 82.46(1)° for 1 and a= 9.045(2), b= 9.149(2), c= 11.621(2)A, α= 74.73(2), β= 80.67(2) and γ= 61.17(1)° for 3. Crystals of 2 are monoclmic, space group P21/c with a= 8.115(1), b= 11.596(2), c= 11.823(3)A, β= 91.57(2)° and Z= 2. The structures of 1 and 2 are made up of dinuclear cations [Co2(H2O)8(bipym)]4+ with nitrate counter ions for 1 and water of crystallization and sulfate groups for 2. The structure of 3 consists of dimeric neutral [Co2(bipym)3(NCS)4] units. Bipyrimidine bridges the cobalt atoms in this series of complexes in a bis(chelating) fashion and a crystallographically imposed inversion centre is located halfway between its two pyrimidyl rings. It is present also as a terminal ligand in 3. The two equivalent cobalt atoms of 1and 2 are each bound to four water oxygens and two cis nitrogens of bipym in a slightly distorted octahedral environment. Each cobalt atom in 3 is bound to six nitrogen atoms belonging to two thiocyanate groups in cis position and to two bipym ligands, one terminal and the other bridging. The intramolecular metal–metal separation varies between 5.761(1) and 5.942(2)A. The magnetic properties of 1–3 have been investigated in the temperature range 4.2–300 K. They all exhibit antiferromagnetic exchange with susceptibility maxima at 13.0–16.4 K. Fits of the magnetic data through the Lines model and the simpler lsing spin-only formalism are compared.
112 citations
TL;DR: The potentially tetradentate ligand 4′-(4-pyridyl)-2,2′ : 6′,2″-terpyridine (pyterpy) acts as a tridentate donor to iron(II), ruthenium(II) and osmium (II) as mentioned in this paper.
Abstract: The potentially tetradentate ligand 4′-(4-pyridyl)-2,2′ : 6′,2″-terpyridine (pyterpy) acts as a tridentate donor to iron(II), ruthenium(II) and osmium(II). The non-co-ordinated pyridyl group reacts with a range of electrophiles to give complexes containing the cationic ligands Hpyterpy and 4′-(4-methylpyridinio)-2,2′ : 6′,2″-terpyridine (mpyterpy) The electrochemical behaviour of these complexes has been studied and correlations between the redox potentials and Hammett σ+ parameters made.
106 citations
TL;DR: In this article, the He I and He II photoelectron spectra were assigned for three closely related molecules, Si(ButNCHCHNBut), Si( ButNCH2CH2NBut) and SiH2(But NCHCHNHBut), providing evidence for an energetically significant contribution from the silicon 3pπ orbital to the ring π system.
Abstract: The He I and He II photoelectron spectra are reported and assigned for three closely related molecules, Si(ButNCHCHNBut), Si(ButNCH2CH2NBut) and SiH2(ButNCHCHNBut), providing evidence for an energetically significant contribution from the silicon 3pπ orbital to the ring π system of Si(ButNCHCHNBut). Theoretical calculations on the model compounds Si(HNCHCHNH), Si(HNCH2CH2NH) and SiH2(HNCHCHNH) have been carried out and there is good agreement between the calculated and experimental geometries. Trends in the orbital energies corresponded closely with the trends found for the ionization energies of the photoelectron bands. Calculated singlet–triplet splittings predict singlet ground states for the model silyienes. Calculated heats of hydrogenation at the ring carbons of Si(HNCHCHNH) and SiH2(HNCHCHNH) show the latter to be more exothermic by 13 kcal mol–1 providing evidence for aromatic cyclic (4n+ 2)-π delocalization in Si(ButNCHCHNBut). Estimates of Si–N double-bond character are obtained by ab initio calculations on rotamers of the model compound Si(NH2)2 and compared with analogous values for C(NH2)2.
91 citations
TL;DR: In this paper, a series of monochelated carboxylatopalladium(II) complexes of general formula [Pd(L−L)(MeCO2)2] and [PD(L −L)(CF3CO2] have been prepared and characterized, and the chemical behavior of the complexes in solution has been studied in different solvents mainly by means of 1H NMR experiments.
Abstract: Two series of monochelated carboxylatopalladium(II) complexes of general formula [Pd(L–L)(MeCO2)2] and [Pd(L–L)(CF3CO2)2][L–L = 1,10-phenanthroline (phen), 2,2′-bipyridine and their substituted derivatives] have been prepared and characterized. The chemical behaviour of the complexes in solution has been studied in different solvents mainly by means of 1H NMR experiments. These showed that, unlike the acetato complexes, the trifluoroacetato derivatives undergo partial dissociation of the anionic ligand in Me2SO solution at room temperature. A similar behaviour was also observed for the acetato complexes in CD3OD. The signals of the H2,9 protons in the phenanthroline series, and those of H6,6 in the bipyridine one, are excellent probes for the evaluation of the environment of the palladium atom. The crystal structures of [Pd(phen)(MeCO2)2], [Pd(2,9-dmphen)(MeCO2)2]·0.40CH2Cl2 and [Pd(2,9-dmphen)(MeCO2)2]·0.25CHCl3](2,9-dmphen = 2,9-dimethyl-1,10-phenanthroline) have been determined. The co-ordination geometry around palladium is square planar in all the structures, but significant deviations from the idealized geometry occur in the last two in order to relieve the interligand contacts. These monochelated carboxylatopalladium(II) complexes are active catalysts in carbon monoxide–olefin copolymerization. Some preliminary results on their catalytic activity are also reported.
85 citations
TL;DR: In this article, a new manganese(II) compound [Mn2(bipy)4(ta)][ClO4]21 has been synthesized and its crystal structure determined by single-crystal X-ray diffraction.
Abstract: A new manganese(II) compound [Mn2(bipy)4(ta)][ClO4]21(bipy = 2,2′-bipyridme, ta = terephthalate dianion) has been synthesised and its crystal structure determined by single-crystal X-ray diffraction. It crystallizes in the triclinic system, space group P, with a= 9.516(2), b= 11.613(3), c= 11.615(3)A, α= 70.92(2), β= 80.16(2), γ= 76.64(2)° and Z= 1. The structure consists of canonic terephthalate-bridged [Mn2(bipy)4(ta)]2+ chains and non-co-ordinated perchlorate anions. Each terephthalate is bound to four manganese atoms through carboxylate oxygens with the sym-sym bridging mode, affording manganese(II) pairs which are linked by the terephthalate group to yield a one-dimensional chain running along the a axis. The intrachain Mn ⋯ Mn separations through the double carboxylate and terephthalate bridges are 4.643(1) and 9.637(2)A, respectively The manganese(II) ion displays a severely distorted octahedral co-ordination being linked to four nitrogen atoms of two bipy ligands and to two oxygen atoms of two carboxylate groups from two terephthalate ligands. The magnetic susceptibility of 1 as a function of temperature (4.2–290 K) exhibits a sharp maximum at 6.0 K which is consistent with a significant antiferromagnetic coupling between the metal centres. This magnetic behaviour has been interpreted in terms of a dimer with a molecular field approximation, the values obtained for J, g and zJ′ being –1.35 cm–1,1.97 and –0.04cm–1, respectively. In the light of the structural data, it can be concluded that the double-carboxylate bridge between the manganese(II) pairs provides a more efficient exchange pathway than that of terephthalate and most likely is responsible for the observed J value.
75 citations
TL;DR: The crystal structures of three series of clathrate compounds with organic guest molecules G have been determined, Cd(CN)2·G, [CdM(CN),4]·2G (M = Hg or Zn) and [NMe4·G][CuM(N), 4] as discussed by the authors, and the cubic Fdmunit cell parameter for the first series (Z= 8) ranges from 12.647(6)A for G = CHCl3 to 12.767(2)A, depending on the molecular size and
Abstract: The crystal structures of three series of clathrate compounds with organic guest molecules G have been determined, Cd(CN)2·G, [CdM(CN)4]·2G (M = Hg or Zn) and [NMe4·G][CuM(CN)4](M = Cd or Zn). The cubic Fdmunit-cell parameter for the first series (Z= 8) ranges from 12.647(6)A for G = CHCl3 to 12.767(2)A for CCl3CF3, depending on the molecular size and orientation of the guest in the cavity. In the second series the space group Fdm is unchanged upon 50% substitution of Cd in the first with Hg or Zn owing to the random distribution of the tetrahedral centres; the lattice parameter varies little when M = Hg, but when M = Zn a= 12.243(2)A, a decrease of 0.5 A from the value for Cd(CN)2·CCl4. The anionic host in the third series accommodates the NMe4+ guest together with neutral CCl4; the lattice parameter of the cubic F3munit cell decreases by ca. 0.6 A in comparison with the values in the first two series. The X-ray data for 24 single crystals are discussed in terms of the crystallographic discrimination between C and N of the linking CN groups and the orientation of the guest molecules, in particular of the tetrahedral and pseudo-tetrahedral guest molecules, in the cavity approximating to a tetrahedron.
75 citations
TL;DR: In this article, the structures of complexes [Au(PPh3)Ph]1, [au2(dppm)Me2]2, [pPh3]Ph2]3 and [{Au[P(C6H4OMe-p)3]}2(µ-CC)]4 were prepared by literature methods.
Abstract: The complexes [Au(PPh3)Ph]1, [Au2(dppm)Me2]2, [Au2(dppm)Ph2]3 and [{Au[P(C6H4OMe-p)3]}2(µ-CC)]4 were prepared by literature methods. The structures of 1–3 have been established by X-ray crystallography: 1, tnclinic, space group P, a= 8.524(2), b= 15.227(2), c= 15.525 A, α= 91.07(1), β= 92.06(1), γ= 94.28(1)°; 2, monoclinic, space group P21/n, a= 12.201(3), b= 13.014(5), c= 16.329(4)A, β= 94.11(2)°; 3, monoclinic, space group C2/c, a= 16.688(3), b= 10.468(1), c= 17.899(2)A, β= 97.70(1)°. The intramolecular Au ⋯ Au distances in 2 and 3 are 3.251(1) and 3.154(1)A respectively. Extended-Huckel molecular orbital calculations showed that the highest occupied molecular orbital of 3 is a combination of dσ* and dδ*, whereas its lowest unoccupied molecular orbital is the π* of the co-ordinated phenyl group. The UV/VIS absorption spectra of 2 and 3 show intense absorptions at around 290–300 nm, which are assigned as Au(dσ*, dδ*)→π*(Ph, dppm) in nature. Both 2 and 3 show luminescence in fluid solution at room temperature. The emission properties of 3 have been examined in detail. Complex 4 shows a well resolved vibronic structured emission at 400–600 nm in dichloromethane at room temperature, arising from the 3[ππ*] excited state of C22–.
TL;DR: In this article, the CH2Cl2 disolvate of 1 is monoclinic, space group P21/n, with a= 1394.33(10), b= 1276.81 (13), c= 2393.08(13) and Z= 4, and the structure was refined to R(Rg)= 0.0351 (0.0384) for 5991 reflections with I > 2.0σ(I).
Abstract: Thermolysis of [7-(CO)-7,7-(PPh3)2-7,1-IrCB7H8]1 at 250 °C resulted in isomerisation to give orange air-stable [7-(CO)-7-H-7,9-(PPh3)2-7,1-IrCB7H7]2 and its 6-(PPh3) isomer 3 as the major products. The compounds were characterised by NMR spectroscopy and single-crystal X-ray diffraction analysis on 1 and 3. The CH2Cl2 disolvate of 1 is monoclinic, space group P21/n, with a= 1394.33(10), b= 1276.81 (13), c= 2393.5(2) pm, β= 94.163(9)°, and Z= 4, and the structure was refined to R(Rg)= 0.0351 (0.0384) for 5991 reflections with I > 2.0σ(I). The CH2Cl2 monosolvate of 3 is triclinic, space group P, with a= 1150.39(11), b= 1177.08(13), c= 1498.3(2) pm, α= 88.192(9), β= 89.506(8), γ= 80.720(9)°, and Z= 2. and the structure was refined to R(Rg)= 0.0299(0.0311) for 5864 reflections with I > 2.0σ(I). The nine-vertex {IrCB7} cluster structures of 1 and 3 have quadrilateral open faces (B–B ca. 220 pm) and therefore ‘isonido’ geometries although of formal closo constitution. The cluster opening is briefly discussed in the context of a nine-vertex closo–isonido–isocloso structural continuum, in the context of other contemporaneously recognised structural continua in twelve-, eleven-, ten-, and eight- vertex boron cluster chemistry, and thence in the context of emerging general structural patterns that interrelate the isocloso, isonido and isoarachno cluster geometries.
Abstract: The synthesis of new metal-free and nickel(II) phthalocyanines substituted with four alkylthio groups SR (R = dodecyl or hexadecyl) is described. The new compounds have been characterized by elemental analyses, and IR, 1H NMR and UV/VIS spectroscopy. The thio donors co-ordinate to AgI and PdII to give 2: 1 metal–nickel phthalocyanine species. The changes in the electronic spectra with respect to increasing concentration of PdII or AgI have been investigated.
TL;DR: In this article, the reaction of [NH4]2[MoO2S2], Cul and NEt4Br in the solid state produced [NEt4]4[Cu6Mo2S6O2Br2I4].
Abstract: The reaction of [NH4]2[MoO2S2], Cul and NEt4Br in the solid state produced [NEt4]4[Cu6Mo2S6O2Br2I4]. Single-crystal X-ray analysis reveals that the cluster anion consists of two nest-shaped fragments interconnected through a Cul2Cu bridge with Cu–I and Cu ⋯ I bond lengths of 2.502 and 2.972 A respectively. The cluster forms monoclinic crystals with space group C2/c, a= 24.423(9), b= 21.021(2), c= 13.715(5)A, β= 114.48(3)° and Z= 4; R= 0.067, R′= 0.087. It exhibits interesting optical-limiting and self-defocusing properties.
TL;DR: In this paper, the reaction of binucleating bridging ligands 3,3′,4,4′-tetrahydroxybiphenyl (H4L1) with 2 equivalents of [Ru(bipy)2Cl2]·2H2O (bipY = 2,2′-bipyridine) results in the formation of binuclear complexes.
Abstract: Reaction of the binucleating bridging ligands 3,3′,4,4′-tetrahydroxybiphenyl (H4L1) or 3,3″,4,4″-tetrahydroxy-p-terphenyl (H4L2) with 2 equivalents of [Ru(bipy)2Cl2]·2H2O (bipy = 2,2′-bipyridine) results in the formation of binuclear complexes [{Ru(bipy)2}(µ-L){Ru(bipy)2}]2+1(L = L1) and 2(L = L2) in which the ligand L4– has been oxidized to the semiquinone (sq) form L2–. In each complex the co-ordinated catecholate fragment (cat) may be oxidised reversibly to the semiquinone and quinone (q) redox states, giving the five-membered redox series cat–cat, cat–sq, sq–sq, sq–q and q–q for the bridging ligands. In the sq–sq state the bridging ligands are necessarily planar due to the presence of double bonds between the aromatic rings; in the cat–cat and q–q states there is formally no double-bond character between the aromatic rings and they are free to adopt a twisted conformation. Spectroelectrochemical measurements confirm that in the cat–cat and q–q states, 1 and 2 behave approximately like their mononuclear counterparts [Ru(bipy)2(cat)] and [Ru(bipy)2(bq)]2+[H2cat = catechol (benzene-1,2-diol); bq =o-benzoquinone]; for 1, the results also show that in the mixed-valence sq–q and sq–cat oxidation states the two halves of the ligand are electronically equivalent (i.e. valence delocalised), which is best explained by the bridging ligand retaining the planar conformation of the sq–sq state. The change from planar to twisted therefore occurs at the extremes of the redox series, on formation of the cat–cat and q–q oxidation states. This control of bridging ligand conformation with oxidation state may form the basis for a molecular switch.
TL;DR: In this paper, the effect of the substituents R (H or Me) and R′ upon the spectroscopic and structural properties of the free ligands and the cyclopalladated complexes is discussed.
Abstract: Ferrocenylimines of general formula [Fe(η5-C5H5)(η5-C5H4CRNR′)](R = Me, R′= Ph 1a, C6H4Me-2 1b, C6H4Me-4 1c, CH2Ph 1d, CH2C6H4Me-2 1e, CH2C6H4Cl-2 1f, CH2CH2Ph 1g or 1-C10H71h; R = H, R′= Ph 1i, C6H4Me-2 1j, C6H4Me-4 1k, CH2C6H4Me-2 1l, CH2C6H4Cl-2 1m or 1-C10H71n) have been prepared and characterized. Addition of these ligands to methanolic solutions of Na2[PdCl4], and sodium acetate trihydrate in a 1 : 1 molar ratio, results in the formation of the di-µ-chloro bridged cyclopalladated complex [{[graphic omitted]R′)](µ-Cl)}2]2a–2n. Reaction of compounds 2a–2n with triphenylphosphine in benzene yields more soluble monocyclopalladated derivatives [[graphic omitted]R′)}Cl(PPh3)]3a–3n. Proton, 13C and 31P NMR spectroscopic studies on these complexes reveal that cyclopalladation occurs on the ferrocenyl moiety, thus producing five-membered metallacycles containing the CN bond (endo-type structures). The crystal structures of compounds 1a, 1i and 3g have been determined. Complex 1a is triclinic, space group P with a= 10.152(3), b= 12.169(3), c= 12.239(3)A, α= 90.45(2), β= 100.56(2) and γ= 102.72(2)°. Compound 1i is monoclinic, space group Cc, with a= 5.876(3), b= 37.298(9), c= 12.640(4)A and β= 103.26(4)°. The complex [[graphic omitted]CH2CH2Ph)}Cl(PPh3)]·CH2Cl23g is monoclinic, space group P21/n with a= 20.343(2), b= 9.133(1), c= 19.714(2)A and β= 97.17(1)°, and its crystal structure confirms the formation of a five-membered palladocycle fused with the ferrocenyl moiety. The influence of the substituents R (H or Me) and R′ upon the spectroscopic and structural properties of the free ligands and the cyclopalladated complexes is also discussed.
TL;DR: In this paper, the 4′-ferrocenyl-2,2′:6′,2″-terpyridine L has been prepared in good yield from ferrocenecarbaldehyde by two different routes.
Abstract: The new ligand 4′-ferrocenyl-2,2′:6′,2″-terpyridine L has been prepared in good yield from ferrocenecarbaldehyde by two different routes. The crystal and molecular structure of L has been determined [monoclinic, space group P21/c, a= 7.905(2), b= 22.045(4), c= 11.394(2)A, β= 107.10(3)°, Z= 4, R= 0.034 for 2486 independent reflections]. The co-ordination behaviour of L has been studied and the homoleptic complexes [ML2][PF6]2(M = Co, Fe or Ru) prepared and characterised. In addition, the heteroleptic complex [RuL(terpy)][PF6]2(terpy = 2,2′:6′,2″-terpyridine) has been prepared. All of these complexes are redox active.
TL;DR: The µ-oxo-bridged diiron(III) complex as mentioned in this paper was found to exhibit monooxygenase-like activity, using H2O2 as the oxidant.
Abstract: The µ-oxo-bridged diiron(III) complex [Fe2O(bipy)4(OH2)2][ClO4]41(bipy = 2,2′-bipyridine) was found to exhibit monooxygenase-like activity, using H2O2 as the oxidant. The system oxidizes alkanes to alcohols and ketones quite efficiently (46 mmol of cyclohexanol + cyclohexanone per rnmol complex in 10 min). In the case of adamantane, selectivity for the tertiary hydrogen was indicated by a high normalized C3:C2 ratio of 9:1. The same reaction yields and rates were obtained whether argon or dioxygen was bubbled through the solution. Dimethyl sulfide was transformed into dimethyl sulfoxide and dimethylsulfone and benzene into phenol. These results exclude O2 as a key reactant in this system and suggest that high-valent oxoiron intermediates and hydroxyl radicals are the active species. The potential of this system is strongly limited by the instability of the catalyst and by its strong catalase-like activity. Complex 1 is actually a very efficient catalyst for hydrogen peroxide dismutation, thus transforming 50% of the excess of H2O2 into O2 in 10 min.
TL;DR: In this paper, three copper(I) complexes with phenazine (phz) were synthesized and their molecular structures and packing determined by single-crystal X-ray diffraction methods.
Abstract: Three copper(I) complexes with phenazine (phz), [{Cu2(µ-X)2(µ-phz)}∞](X = l 1, Br 2 or Cl 3) were synthesized and their molecular structures and packing determined by single-crystal X-ray diffraction methods. The copper atoms of the Cu2I2 rhomboid in 1 are bridged by phz molecules to give an infinite linear chain and the phz molecules overlap between the infinite chains with an interplanar spacing of 3.46 A. Compounds 2 and 3 have two-dimensional sheets of hanging phz molecules between polymeric stair frameworks of CuBr and CuCl, respectively. The interplanar spacings of adjacent phz molecules for 2 and 3 are 3.40 and 3.36 A, respectively. All three complexes exhibit an absorption band at about 710 nm characteristic of copper(I) co-ordination polymers with phz.
TL;DR: In this paper, the solid-state crystal structure of Na[Y(dota)(H2O)]·4H 2O (H4dota = 1,4,7,10-tetraazacyclododecane-N,N′, N″,N″, N‴-Tetraacetic acid) at 115 K has been obtained together with the solution structure of the neutral zirconium complex.
Abstract: The solid-state crystal structure of Na[Y(dota)(H2O)]·4H2O (H4dota = 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid) at 115 K has been obtained together with the solution structure of the neutral zirconium complex. The yttrium complex shows a mono-capped (H2O) square-antiprismatic structure while the solution 1H NMR spectra of [Zr(dota)(H2O)] suggest that a structure of lower symmetry is adopted and a minor isomer is observed. The crystal structure of the yttrium complex of N,N″-bis(benzylcarbamoylmethyl)diethylenetriamine-N,N′,N″-triacetic acid has revealed amide carbonyl ligation in a distorted mono-capped square-antiprismatic structure, with one metal-bound water molecule.
TL;DR: In this paper, metallophthalocyanines (M = Cu or Ni) substituted in peripheral positions with four 14-membered tetraaza macrocycles each attached to a 15membered crown ether have been prepared in a multi-step reaction sequence.
Abstract: New metallophthalocyanines (M = Cu or Ni) substituted in peripheral positions with four 14-membered tetraaza macrocycles each attached to a 15-membered crown ether have been prepared in a multi-step reaction sequence. The N-tosylated derivatives are extensively soluble in apolar solvents and form adducts with alkali-metal cations. Detosylation of the macrocyclic aza groups provides donor sites for binding transition-metal ions (e.g. NiII) which leads to pentanuclear water-soluble complexes.
TL;DR: In this article, the tridentate thiosemicarbazone ligand acts as a bridging ligand occupying the apical position of the symmetric copper atom in the dimeric structure.
Abstract: The compounds [{CuL(X)}2](X = Cl 1 or Br 2, HL = pyridine-2-carbaldehyde thiosemicarbazone) have been synthesised and structurally characterized. Both crystallize in the triclinic space group P. For compound 1, a= 7.915(3), b= 8.262(5), c= 9.016(2)A, α= 67.97(3), β= 92.26(2), γ= 71.33(4)°, Z= 2, R= 0.046, R′= 0.054. For 2, a= 7.617(1), b= 8.451(3), c= 8.966(2)A, α= 68.50(2), β= 95.94(1), γ= 71.73(2)°, Z= 2, R=R′= 0.035. The copper(II) ions have square-pyramidal environments with the tridentate thiosemicarbazone ligands and the halide atoms in an equatorial position. The sulfur atom of the tridentate ligand acts as a bridging ligand occupying the apical position of the symmetric copper atom in the dimeric structure. Such a disposition of the sulfur bridges is very scarce. Q-Band ESR spectra of the two compounds show rhombic signals with g1= 2.183, g2= 2.053, g3= 2.033 for 1 and g1= 2.161, g2= 2.057, g3= 2.033 for 2. Magnetic measurements on 1 and 2 show antiferromagnetic couplings between the copper(II) cations through the sulfur bridges. The exchange parameter is J/k=–6.8K (–4.7 cm–1). Magnetostructural correlations have been analysed by using extended Huckel molecular orbital calculations.
TL;DR: In this article, the rate of terpyridine fluxion was measured by NMR spectroscopy from the exchange effects on the 1H signals of the aromatic hydrogens and in the 19F signals of two C6F5 groups.
Abstract: 2,2′:6′,2″-Terpyridine reacted with trans-[M(C6F5)2(diox)2](M = Pd or Pt, diox = 1,4-dioxane) to form the square-planar complexes cis-[M(C6F5)2(terpy)] in which the terpyridine acts as a bidentate chelate ligand. In solution these complexes are fluxional with the terpyridine oscillating between equivalent bidentate modes by a mechanism consisting of a ‘tick-tock’ twist of the metal moiety through an angle equal to the N–M–N angle of the metal centre. Rates of this fluxion were measured by NMR spectroscopy from the exchange effects on the 1H signals of the aromatic hydrogens and in the 19F signals of two C6F5 groups. The ΔG‡ values for the fluxion were ca. 71 and 94 kJ mol–1 for the complexes of PdII and PtII respectively. At below-ambient temperatures further changes in the 19F NMR spectra of both complexes were interpreted in terms of varying rates of rotation of the unco-ordinated pyridine ring, with the rates of rotation of the C6F5 rings being substantially slower at all temperatures and not separately measurable. The lowest-temperature spectra suggested the presence of a pair of degenerate rotamers each having the planes of both C6F5 rings and the unco-ordinated pyridine ring closely parallel and orthogonal to the remainder of the ligand ring system. The crystal structure of [Pd(C6F5)2(terpy)] confirms the bidentate chelate bonding of terpy with a N–Pd–N angle of 77.9°, and the pendant ring oriented at an angle of 46° to the adjacent co-ordinated ring.
TL;DR: In this article, the crystal and molecular structures of trinuclear cluster salts were determined in the presence of NaBF4 and in the absence of an additional salt, under high pressure conditions (60 atm, 55 °C).
Abstract: The low-pressure hydrogenation of the hydrolysis mixture of [Ru2(η6-C6H6)2Cl4] in water (1.5 atm, 20 °C) led, in the presence of NaClO4, to the oxo-capped trinuclear cluster cation [Ru3(η6-C6H6)3(µ-Cl)(µ3-O)(µ-H)2]+1 which crystallized as the perchlorate salt. The chloro-capped trinuclear cluster cation [Ru3(η6-C6H2Me-1,2,4,6)3(µ3-Cl)H3]2+2, crystallized as the dichloride, was accessible from the durene derivative [Ru2(η6-C6H2Me-1,2,4,6)2Cl4] by high-pressure hydrogenation (60 atm, 55 °C) in water. In hot aqueous solution, the chloro-capped cluster 2 underwent hydrolysis to give the oxo-capped cluster [Ru3(η6-C6H2Me4-1,2,4,6)3(µ3-O)H3]+3. In the presence of NaBF4, the low-pressure hydrogenation (1.5 atm, 20 °C) of the hydrolysis mixture of [Ru2(η6-C6H6)2Cl4] led to the tetranuclear tetrahydrido cluster cation [Ru4(η6-C6H6)4H4]2+4 which precipitated as the tetrafluoroborate salt. Under high-pressure conditions (60 atm, 55 °C) and in the absence of an additional salt, the hexahydrido cluster cation [Ru4(η6-C6H6)4H6]2+5 was formed and obtained as the dichloride. By analogy, the p-cymene derivative [Ru2(η6-C6H4MePri-p)2Cl4] gave [Ru4(η6-C6H4MePri-p)4H6]2+6. In contact with air, the hexahydrido clusters 5 and 6 were transformed into the corresponding tetrahydrido clusters [Ru4(η6-C6H6)4H4]2+4 and [Ru4(η6-C6H4MePri-p)4H4]2+7. The hexahydrido cluster 5 is capable of hydrogenating fumarie acid to give succinic acid and 4; the latter adds molecular hydrogen to regenerate the hexahydrido species 5. The crystal and molecular structures of the cluster salts [Ru3(η6-C6H6)3(µ-Cl)(µ3-O)(µ-H)2]ClO4(cation 1), [Ru3(η6-C6H2Me4-1,2,4,6)3(µ3-O)H3]BF4(cation 3), [Ru4(η6-C6H6)4H4]Cl2(cation 4) and [Ru4(η6-C6H4MePri-p)4H6][ClO4]2(cation 6) have also been determined.
TL;DR: In this paper, a series of nine [M(CO)5(EPh3)] complexes (M = Cr, Mo or W; E = P, As or Sb) were analyzed and the trends in bond lengths and angles were rationalised in terms of steric and electronic interactions between the bonded M( CO)5 and EPh3 fragments.
Abstract: Crystal structures have been determined for [W(CO)5(PPh3)], [M(CO)5(AsPh3)] and [M(CO)5-(SbPh3)](M = Mo or W) as part of a systematic study of a series of nine [M(CO)5(EPh3)] complexes (M = Cr, Mo or W; E = P, As or Sb). Trends in bond lengths and angles are rationalised in terms of steric and electronic interactions between the bonded M(CO)5 and EPh3 fragments. Comparison is made between the solid-state geometry of the free and co-ordinated EPh3. Torsion angles defining the disposition of the EPh3 groups in relation to M(CO)5 show little variation within the [M(CO)5(EPh3)] series. For all nine complexes the EPh3 groups have propeller geometry with small deviations from symmetric C3 structures. The studies were extended to include other related [M(CO)5L] complexes. Trends in the structural parameters of 29 such compounds are related to the steric behaviour and π-acceptor capacity of the ligands L. It is shown that M–P bond dimensions are not adequately explained by hybridisation changes of the phosphorus atom in the ligand L.
TL;DR: In this paper, an unsymmetric phenol-based dinucleating ligand with amino and imino chelating arms formed dinuclear manganese(II) complexes [Mn2L(RCO2)2(NCS)](L = L1 or L2, R = Me or Ph).
Abstract: Unsymmetric phenol-based dinucleating ligands with amino and imino chelating arms, 4-bromo-2-{[(2-dimethylaminoethyl)methylamino]methyl}-6-[2-(dialkylamino)ethyliminomethyl]phenolate(1–)[alkyl = methyl (L1) or ethyl (L2)], formed dinuclear manganese(II) complexes [Mn2L(RCO2)2(NCS)](L = L1 or L2, R = Me or Ph). The complex [Mn2L2(MeCO2)2(NCS)] crystallizes in the monoclinic space group P21/n, a= 13.450(2), b= 18.743(3), c= 12.662(2)A and β= 102.08(1)°. An X-ray diffraction analysis revealed that the dinuclear core structure is bridged by the phenolic oxygen of L2 and by two acetate groups. The unsymmetric ligand provides different co-ordination geometries about the two manganese ions. The geometry of Mn at the imine site is distorted trigonal bipyramidal with the imine N and the two acetate O atoms in the basal plane and the phenolic O and the terminal N at the axial sites. The geometry of the Mn at the amine site is distorted octahedral involving also the nitrogen of the isothiocyanato group. Magnetic susceptibility measurements over the temperature range 4.2–300 K indicated weak antiferromagnetic interaction (J=–3 to –5 cm–1 based on Ĥ=–2JS1·S2). Cyclic voltammetry for [Mn2L1(MeCO2)2(NCS)] in CH2Cl2 revealed three quasi-reversible redox couples (E½= 0.63, 1.07 and 1.24 V vs. saturated calomel electrode) assignable to the stepwise oxidations MnIIMnII→ MnIIMnIII→MnIIIMnIII→MnIIIMnIV. All the complexes show a catalase-like activity, disproportionating H2O2 into O2 and H2O. The presence of oxomanganese(IV) intermediates is suggested based on visible and mass spectrometric investigations.
TL;DR: The emissive one-dimensional gold(I) polymer [{Au2L(CCPh)2}∞], L = 2,6-bis(diphenylphosphino)-pyridine] has been prepared and its crystal structure determined.
Abstract: The emissive one-dimensional gold(I) polymer [{Au2L(CCPh)2}∞][L = 2,6-bis(diphenylphosphino)-pyridine] has been prepared and its crystal structure determined; Au2L(CCPh)2is the repeating unit and the closest intermolecular AuI⋯ AuI separation is 3.252(1)A.
TL;DR: In this paper, the structure of the tridentate Schiff-base ligands and the two heterocyclic nitrogen atoms of py or bipy co-ordinate in equatorial and axial positions, completing an octahedral geometry around the vanadium.
Abstract: The complex [VO(salgly)(H2O)] 1 dissolved in pyridine (py) to form brown [VO(salgly)(py)2]2(salgly =N-salicylideneglycinate). A brown complex [VO(sal-L-ala)(bipy)]3 precipitated on adding 2,2′-bipyridine (bipy) to [VO(sal-L-ala)(H2O)]4(sal-L-ala =N-salicylidene-L-alaninate) in methanol. The structures of 2 and 3 have been determined by X-ray diffraction analysis. In both the tridentate Schiff-base ligands occupy equatorial positions and the two heterocyclic nitrogen atoms of py or bipy co-ordinate in equatorial and axial positions, completing an octahedral geometry around the vanadium. The circular dichroism spectra of 3 dispersed in Nujol and in methanolic solutions are very similar. This finding together with EPR and thin-layer chromatographic experiments suggests that 3 is relatively stable to hydrolysis and that its structures in the solid state and solution are similar. Complex 2 and [VO(sal-L-ala)(py)n] are not as stable to hydrolysis as 3 and a solid formulated as [VO(salgly)(py)(H2O)] was also isolated.