Dependence of the chemical properties of macrocyclic [Ni(II)(2)L(μ-O(2)CR)](+) complexes on the basicity of the carboxylato coligands (L(2-) = macrocyclic N(6)S(2) ligand)

The dependence of the properties of mixed ligand [Ni(II)(2)L(μ-O(2)CR)](+) complexes (where L(2-) represents a 24-membered macrocyclic hexaamine-dithiophenolato ligand) on the basicity of the carboxylato coligands has been examined. For this purpose 19 different [Ni(II)(2)L(μ-O(2)CR)](+) complexes (2-20) incorporating carboxylates with pK(b) values in the range 9 to 14 have been prepared by the reaction of [Ni(II)(2)L(μ-Cl)](+) (1) and the respective sodium or triethylammonium carboxylates. The resulting carboxylato complexes, isolated as ClO(4)(-) or BPh(4)(-) salts, have been fully characterized by elemental analyses, IR, UV/vis spectroscopy, and X-ray crystallography. The possibility of accessing the [Ni(II)(2)L(μ-O(2)CR)](+) complexes by carboxylate exchange reactions has also been examined. The main findings are as follows: (i) Substitution reactions between 1 and NaO(2)CR are not affected by the basicity or the steric hindrance of the carboxylate. (ii) Complexes 2-20 form an isostructural series of bisoctahedral [Ni(II)(2)L(μ-O(2)CR)](+) compounds with a N(3)Ni(μ-SR)(2)(μ-O(2)CR)NiN(3) core. (iii) They are readily identified by their ν(as)(CO) and ν(s)(CO) stretching vibration bands in the ranges 1684-1576 cm(-1) and 1428-1348 cm(-1), respectively. (iv) The spin-allowed (3)A(2g) → (3)T(2g) (ν(1)) transition of the NiOS(2)N(3) chromophore is steadily red-shifted by about 7.5 nm per pK(b) unit with increasing pK(b) of the carboxylate ion. (v) The less basic the carboxylate ion, the more stable the complex. The stability difference across the series, estimated from the difference of the individual ligand field stabilization energies (LFSE), amounts to about 4.2 kJ/mol [Δ(LFSE)(2,18)]. (vi) The "second-sphere stabilization" of the nickel complexes is not reflected in the electronic absorption spectra, as these forces are aligned perpendicularly to the Ni-O bonds. (vii) Coordination of a basic carboxylate donor to the [Ni(II)(2)L](2+) fragment weakens its Ni-N and Ni-S bonds. This bond weakening is reflected in small but significant bond length changes. (viii) The [Ni(II)(2)L(μ-O(2)CR)](+) complexes are relatively inert to carboxylate exchange reactions, except for the formato complex [Ni(II)(2)L(μ-O(2)CH)](+) (8), which reacts with both more and less basic carboxylato ligands.     

Synthesis and Crystal Structure of (L)2W(CO)4·CH3COCH3 (L = 1-Phenacylimidazole)

The reaction of 1-phenacylimidazole with W(CO)6 in a 1:1 molar ratio under irra- diation with a high-pressure Hg lamp mainly yielded the title compound (C29H26N4O7W, Mr = 726.39), which is of orthorhombic, space group Pbca with a = 27.665(4), b = 7.7807(12), c = 27.803(4) (A), V = 5984.8(16) (A)3, Z = 8, Dc = 1.612 g/cm3, λ(MoKα) = 0.71073 (A), μ = .3.911 mm-1, F(000) = 2864, R = 0.0583 and wR = 0.1502 for 3356 observed reflections (I > 2σ(I)). The crystal structural analysis indicates that in the coordination geometry of tungsten, 1-phenacylimidazole acts as a monodentate ligand and two imidazole ligands locate in a cis-position.     

Cobalt (iron) thiolato complexes containing the Co-ligand phosphine and reaction products of the structural fragment ML 2 L′ (L = 1,2-bidentate thiolate,L′= tertiary phosphine)

Mono-, di-, tri-, and tetra-nuclear cobalt (iron) complexes containing co-ligands phosphine and thiolate are presented according to the classification by combination of different dentates of the two ligands. Emphasis is being put on the triand tetranuclear cluster complexes of monodentate phosphines and 1,2-bidentate thiolates. These complexes are considered to be constructed based on the general structural fragment (or building block) ML ₂L (L=1,2-bidentate thiolate,L=tertiary phosphine). Structural regularities are presented in Tables I, III, IV, and V and discussed. FAB mass spectroscopic data showed the possible fragmentation patterns. Synergism of the cluster skeletons is proposed to explain the occurrence of the distinct structural modes.Abbreviations Bu _n ³ P tri-n-butylphosphine - dmpe 1,2-bis(dimethylphosphino)ethane - dmpm 1,2-bis(dimethylphosphino)methane - dppe 1,2-bis(diphenylphosphino)ethane - dppep bis(2-diphenylphosphinoethyl)phenylphosphine - dppm 1,1-bis(diphenylphosphino)methane - dppp 1,3-bis(diphenylphosphino)propane - Et₃P triethylphosphine - Ph₃P triphenylphosphine - tepme 1,1,1-tris(diethylphosphinomethyl)ethane - tppme 1,1,1-tris(diphenylphosphinomethyl)ethane - H₂bdt 1,2-benzenedithiol - H₂edt 1,2-ethanedithiol - Hmbt 2-mercaptobenzothiazole - H₂mp 2-mercaptophenol - Hmp 2-hydroxythiophenolate - Hmpo 2-mercaptopyridine-N-oxide - H₂mpp 2-mercapto-3-hydroxypyridine - Hmpp 3-hydroxy-2-pyridinothiolate - H₂pdt 1,2-propanedithiol - HSPh thiophenol - H₂tdt 4-methyl-1,2-benzenedithiol(4-toluenedithiol) - R₂dtc dialkyldithiocarbamate - (RO)₂dtp dialkyldithiophosphate     

Semiclassical glory analyses in the time domain for the H + D2(v(i) = 0, j(i) = 0) → HD(v(f) = 3, j(f) = 0) + D reaction

We make the first application of semiclassical (SC) techniques to the plane-wavepacket formulation of time-domain (T-domain) scattering. The angular scattering of the state-to-state reaction, H + D(2)(v(i) = 0, j(i) = 0) → HD(v(f) = 3, j(f) = 0) + D, is analysed, where v and j are vibrational and rotational quantum numbers, respectively. It is proved that the forward-angle scattering in the T-domain, which arises from a delayed mechanism, is an example of a glory. The SC techniques used in the T-domain are: An integral transitional approximation, a semiclassical transitional approximation, a uniform semiclassical approximation (USA), a primitive semiclassical approximation and a classical semiclassical approximation. Nearside-farside (NF) scattering theory is also employed, both partial wave and SC, since a NF analysis provides valuable insights into oscillatory structures present in the full scattering pattern. In addition, we incorporate techniques into the SC theory called "one linear fit" and "two linear fits", which allow the derivative of the quantum deflection function, Θ?(')(J), to be estimated when Θ?J exhibits undulations as a function of J, the total angular momentum variable. The input to our SC analyses is numerical scattering (S) matrix data, calculated from accurate quantum collisional calculations for the Boothroyd-Keogh-Martin-Peterson potential energy surface No. 2, in the energy domain (E-domain), from which accurate S matrix elements in the T-domain are generated. In the E-domain, we introduce a new technique, called "T-to-E domain SC analysis." It half-Fourier transforms the E-domain accurate quantum scattering amplitude to the T-domain, where we carry out a SC analysis; this is followed by an inverse half-Fourier transform of the T-domain SC scattering amplitude back to the E-domain. We demonstrate that T-to-E USA differential cross sections (DCSs) agree well with exact quantum DCSs at forward angles, for energies where a direct USA analysis in the E-domain fails.     

Determination of Ki (i = 1–3) and μj (j = 2–6) in 5CB by observing the angular dependence of Rayleigh line spectral widths

Abstract

Using Parodi's relation, all of the Leslie viscosity coefficients, except μ₁, together with the Frank elastic constants have been measured successfully by the photon correlation spectroscopy of Rayleigh scattered light. The values so determined are in good agreement with those previously determined from shear flow experiments by Chmielewski and by Skarp et al. The polar angle dependence of mode 1 spectral width is proposed as a novel method for the measurement of μ₁ and for the experimental confirmation of Parodi's relation.     

The preparation and spectral properties of the new ‘mixed’ complexes [MI2(CO)3(py)L] (M = Mo and W; L = PPh3, AsPh3 and SbPh3)

Abstract

Seven-coordinate complexes of molybdenum(II) and tungsten(II) have become increasingly important as homogeneous catalysts. For example, the complexes [MX₂(CO)₃L₂] (M = Mo and W; X = Cl and Br; L = PPh₃ and AsPh₃) have been shown to be catalysts for the ring-opening polymerisation of norbornene.¹ Although a wide variety of complexes of the type [MX₂(CO)₃L₂] (M = Mo and W; X = Cl, Br and I; L = nitrogen, phosphorus, arsenic and antimony donor ligands)² have been reported, until now no examples of the mixed complexes [MX₂(CO)₃(py)L] have been prepared. In this communication we wish to describe the synthesis of the new mixed pyridine/L compounds [MI₂(CO)₃(py)L] (M = Mo and W; L = PPh₃, AsPh₃ and SbPh₃).     

Co(III) and Cr(III) complexes of diphosphadithia ligands and the crystal structure of [CoCl2(L3)]PF6·CH2Cl2 (L3=Ph2P(CH2)2S(o-C6H4)S(CH2)2PPh2)

[CrX₃(thf)₃] (X=Cl or Br) reacts with L (L=L¹–L³ or Ph₂[14]aneP₂S₂) (L¹=Ph₂P(CH₂)₂S(CH₂)₂S(CH₂)₂PPh₂, L²=Ph₂P(CH₂)₂S(CH₂)₃S(CH₂)₂PPh₂, L³=Ph₂P(CH₂)₂S(o-C₆H₄)S(CH₂)₂PPh₂, Ph₂[14]aneP₂S₂=4,8-diphenyl-1,11-dithia-4,8-diphosphacyclotetradecane) and TlPF₆ in MeNO₂ solution to yield the distorted octahedral complexes [CrX₂(L)]PF₆ as green coloured solids in high yield. UV/visible spectroscopy suggests that these are cis-dihalo species and they have also been characterised by IR spectroscopy, electrospray mass spectrometry and microanalyses. The Co(III) analogues [CoX₂(L)]⁺ are readily prepared in a two-stage reaction, involving treatment of CoX₂·6H₂O with L (L=L¹–L³) and NH₄PF₆ in EtOH solution to give a green/brown solid, followed by halogen oxidation of this product in CH₂Cl₂ solution using X₂/CCl₄, to give the final products as brown coloured solids. A mixture of PF₆⁻ and [CoX₄]²⁻ anions are present in the final Co(III) compounds in varying ratios. Crystal structures of [CoCl₂(L²)]₂[CoCl₄]·4H₂O and [CoCl₂(L³)]PF₆·CH₂Cl₂ confirm tetradentate P₂S₂ coordination of L in each case, with mutually cis halogens completing the distorted octahedral geometry. In both cases the complex cation adopts the cis-α form in the solid state and this is also consistent with the solution ³¹P{¹H} NMR spectroscopic data. ⁵⁹Co NMR spectroscopy reveals a very broad single resonance at ≈3200 ppm for these species.     

Synthesis and Crystal Structure of an Azido-Bridged Cadmium(II) Dimer [L2Cd2(μ-N3)2(N3)2] (L=1,4,7-Triazacyclononane)

A new dinuclear Cd(II) complex, [L₂Cd₂(μ-N₃)₂(N₃)₂], containing two end-on bridging azide ligands, two monodentate N₃ ligands and 1,4,7-triazacyclononane as the capping ligand, has been synthesized and its structure determined by X-ray crystallography. The complex crystallizes in the monoclinic space group P2₁/c with a=8.467(3), b=14.359(5), c=10.115(4)Å, β=95.026(6)° and z=4. The cadmium(II) centre is six-coordinate with distorted octahedral geometry, bonded to three N atoms of the 1,4,7-triazacyclononane, two nitrogen atoms of μ-azide bridges and one nitrogen atom of a monodentate azide ligand. Neighboring Cd(II) atoms are linked by the double end-on azide bridges.     

Synthesis and Crystal Structure of (L)_2W(CO)_4·CH_3COCH_3 (L=1-Phenacylimidazole)

1 INTRODUCTION Due to their variability in binding modes, five- membered heterocyclic ligands such as pyrazole[1] and 1,2,4-triazole[2] have been drawn much attention. Consequently, there are numerous reports on their derivatives. Imidazoles resemble pyrazoles, and they are isomeric five-membered heterocyclic molecules containing two nitrogen atoms. Furthermore, imida- zole is also a ring component of adenine and purine, one of the most versatile binding sites in biological systems, so th…     

Complexes of the type Mo2(O2CR)2X2(LL) In which the bidentate phosphine ligands LL Straddle the MoMo bond

The reactions of Mo₂(O₂CCH₃)₂Cl₂(PPh₃)₂ with the bidentate phosphine ligands Ph₂PCH₂CH₂PPh₂(dppe), Ph₂PCHCHPPh₂(dppee) and o-C₆H₄(PPh₂)₂(dppbe) yield purple complexes of the stoichiometry Mo₂(O₂CCH₃)₂X₂(LL) in which the acetate ligands are believed to be cis and the LL ligands bridge the dimolybdenum core so that their P atoms are anti to one another. The relationship of these complexes to the previously reported complex Mo₂(O₂CCH₃)₂Cl₂(dppm), where dppm = Ph₂PCH₂PPh₂, is discussed. These complexes have been characterized on the basis of their electrochemical redox properties, and electronic absorption and NMR (¹H and ³¹P{¹H}) spectral measurements.     

The Synthesis and Structure of Herbicidal Mononuclear Cobalt (Ⅱ) Sulfonylurea Complex CoL2 (L=Sulfometuron-methyl Anion)

A number of sulfonylureas are commercialized ALS-inhibiting herbicides to control broad-spectrum weeds in various crops when applied at very low dosage (5-50 g/ha)^[l]. But little sulfonylurea complex is investigated in the literature. Previously we reported the preparation and herbicidal activity of (Chlorsulfuron)₂Cu(OAc)₂^[2]. Herein we report the preparation and structure study of the following novel sulfonylurea cobalt (Ⅱ) complex to study its herbicidal activity:     

The reactions of [MI2(CO)3(NCMe)2] (M = Mo or W) with one equivalent of L (L = pyridine or substituted pyridines) to give [WI2(CO)3(NCMe)L] and [M(μ-I)I(CO)3L]2

The complexes [MI₂(CO)₃(NCMe)₂] (M = Mo or W) react with one equivalent of L in CH₂Cl₂ at room temperature to give initially the mononuclear seven-coordinate complexes [MI₂(CO)₃(NCMe)L] which have been isolated for M = W; L = 3Cl-py, 3Br-py, 4Cl-py and 4Br-py. These compounds dimerise to give the iodidebridged dimers [M(μ-I)I(CO)₃L]₂ by displacement of acetonitrile. When M = Mo; L = 3Cl-py, 3Br-py, 4Cl-py and 4Br-py, and when M = Mo and W; L = py, 2Me-py (for M = W only), 4Me-py, 3,5-Me₂-py, 2Cl-py and 2Br-py, only the dimeric complexes have been isolated. The ease of dimerisation of [MI₂(CO)₃(NCMe)L] is discussed in terms of the steric and electronic effects of the substituted pyridines.     

Synthesis and structures of the six-coordinate donor-acceptor complexes R3(C6H4O2)Sb…L (R=Ph, L=OSMe2 or ONC5H5; R=Me, L=ONC5H5 or NC5H5) and R3(C2H4O2)Sb…L (R=Ph, L=ONC5H5; R=Cl or C6F5, L=OPPh3)

One-pot oxidation of R₃Sb (R=Ph, Me, Cl, or C₆F₅) withtert-butyl hydroperoxide in the presence of 1,2-diols and monodentate donor compounds was studied. The structures of the resulting neutral organic donor-acceptor Sb^V complexes, Ph₃(C₆H₄O₂)Sb…OSMe₂, Ph₃(C₆H₄O₂)Sb…ONC₅H₅, Me₃(C₆H₄O₂)Sb…ONC₅H₅, Me₃(C₆H₄O₂)Sb…NC₅H₅, Ph₃(C₂H₄O₂)Sb…ONC₅H₅, and Cl(C₆F₅)₂(C₂H₄O₂)Sb…OPPh₃, were established by X-ray diffraction analysis. In these complexes, the coordination environment about the Sb atoms is a distorted octahedron. The Sb?O(N) distances and the Sb?O?E angles (E=S, N, or P) vary over wide ranges.     

Synthesis of optically active Zn(II) complexes with thiosemicarbazones of (+)-camphor (L) and (−)-carvone (L1). The crystal structures of L and [Zn(L)2Cl2]

The optically active complexes [Zn(L)₂Cl₂] (I) and [Zn(L¹)₂Cl₂] (II) (L and L¹ are thiosemicar-bazones of (+)-camphor and (?)-carvone, respectively) were obtained. The crystal structures of L and complex I were determined by X-ray diffraction. The structure of L consists of hydrogen-bonded molecules united into chains. The crystal structure of complex I is built from mononuclear molecules. The coordination polyhedron of the Zn atom is a distorted tetrahedron Cl₂S₂. The molecule L functions as a monodentate ligand. According to data from IR spectroscopy, complex II is structurally similar to complex I.     

Nickel(II) hydride and fluoride pincer complexes and their reactivity with Lewis acids BX3·L (X = H, L = thf; X = F, L = Et2O)

Reaction of the pincer hydride complex ((tBu)PCP)Ni(H) [(tBu)PCP = 2,6-C(6)H(3)(CH(2)P(t)Bu(2))(2)] with BH(3)·thf in THF at 190 K generates the corresponding borohydride complex ((tBu)PCP)Ni(BH(4)). The kinetically stable (but thermodynamically unstable) species undergoes reversible borane loss. The related fluoride complex ((tBu)PCP)Ni(F) shows the same reactivity towards BF(3)·Et(2)O, producing ((tBu)PCP)Ni(BF(4)) as the main final product. The processes were followed through multinuclear NMR spectroscopy and DFT calculations, at the M06//6-31+G(d,p) level of theory.     

Crystal and molecular structure of the [Zn(HL)Cl]·EtOH compound, (H2L = chiral bis(menthane)propylenediaminodioxime)

The crystal structure of a solvate [Zn(HL)Cl]·EtOH is determined by single crystal X-ray crystallography (150 K, Bruker X8 Apex CCD autodiffractometer, MoK _α radiation). The crystals are triclinic, unit cell parameters are: a = 7.4755(4) Å, b = 13.9701(11) Å, c = 14.4593(19) Å, α = 82.277(2)°, β = 75.410(2)°, γ = 75.356(1)°, space group P1. The structure of the solvate contains two crystallographically independent complex [Zn(HL)Cl] molecules and two non-coordinated ethanol molecules. In each of the molecules, Zn²⁺ ions coordinate N atoms of tetradentate chelating ligands HL^? and a Cl atom. ClN₄ polyhedra have a distorted tetragonal pyramidal geometry. EtOH molecules make H-bonds with the complex molecules, thus facilitating the formation of chains along the x axis.     

Copper(II), nickel(II) and palladium(II) complexes of the diamide ligand N,N′-bis(2-carbamoylethyl)ethylenediamine (H2L) and the crystal structure of the carbonyl-oxygen-bonded copper(II) complex [Cu(H2L)](ClO4)2

The preparation of the diamide ligand N,N-bis(2-carbamoylethyl)ethylenediamine (H2L) by Michael addition of ethylenediamine to acrylamide is described. The copper(II) complex [Cu(H2L)](ClO4)2 and the deprotonated complex [CuL]·H2O have been prepared and characterized as has the blue octahedral nickel(II) complex [Ni(H2L)](ClO4)2. The crystal structure of the carbonyl-oxygen-bonded copper(II) complex [Cu(H2L)] (ClO4)2 has been determined (R=5.5%). The stepwise protonation equilibria of the ligand have been studied by potentiometric titration, giving values of logK1= 8.71 and logK2=5.74 at 25°C and I=0.1moldm–3 (NaClO4). The interaction of copper(II) with the ligand (H2L/Cu(II)=1:1) can be fitted to the set of equilibria:With nickel(II), only two complexes, [Ni(H2L)]2+ and [NiL], occur and they have formation constants of log110=7.39 and log 11–2=–11.49. With palladium- (II) the system is similar to that with copper(II) with three complex species, 110, 11–1 and 11–2, with log 110=15.48, log 11–1=11.88 and log 11–2=7.32.     

Theoretical Investigations on the Structures and Properties of the Side-on Complexes B_2(N_2)_2 and Monocyclic B_n(N_2)_n~m (n=3～6,m=-1～+2)

The structures and energies of the side-on complexes B2(N2)2 and monocyclic Bn(N2)nm (n = 3～6,m = -1～+2) between N2 (1∑+g) and B (2P) have been investigated by the DFT-B3LYP and MP2 methods at the 6-311+G(2d) and aug-cc-pVTZ levels. The analyses of NICS (Nucleus Independent Chemical Shifts),NBO (nature bond orbital),AIM (atoms in molecules) and frontal orbitals have been used to reveal the origin of coordination bond between the π-electron donor N2 group and B atom,accompanied by the comparison with the end-on complexes. The results have indicated that the side-on coordination complexes can be formed due to the relative strong fluidity of the π-electrons,and the nature of the coordination bond has been exposed to be that the N2 group offers 1πu electron to the 2p orbital of boron. The coordinate energies of the side-on complexes are less than those of the end-on complexes. Furthermore,the aromaticity of side-on coordination complex is weaker than that of the corresponding end-on coordination complex.     

Kinetic (T = 201-298 K) and equilibrium (T = 320-420 K) measurements of the C3H5 + O2 ⇆ C3H5O2 reaction

The kinetics and equilibrium of the allyl radical reaction with molecular oxygen have been studied in direct measurements using temperature-controlled tubular flow reactor coupled to a laser photolysis/photoionization mass spectrometer. In low-temperature experiments (T = 201-298 K), association kinetics were observed, and the measured time-resolved C(3)H(5) radical signals decayed exponentially to the signal background. In this range, the determined rate coefficients exhibited a negative temperature dependence and were observed to depend on the carrier-gas (He) pressure {p = 0.4-36 Torr, [He] = (1.7-118.0) × 10(16) cm(-3)}. The bimolecular rate coefficients obtained vary in the range (0.88-11.6) × 10(-13) cm(3) s(-1). In higher-temperature experiments (T = 320-420 K), the C(3)H(5) radical signal did not decay to the signal background, indicating equilibration of the reaction. By measuring the radical decay rate under these conditions as a function of temperature and following typical second- and third-law procedures, plotting the resulting ln K(p) values versus 1/T in a modified van't Hoff plot, the thermochemical parameters of the reaction were extracted. The second-law treatment resulted in values of ΔH(298)° = -78.3 ± 1.1 kJ mol(-1) and ΔS(298)° = -129.9 ± 3.1 J mol(-1) K(-1), with the uncertainties given as one standard error. When results from a previous investigation were taken into account and the third-law method was applied, the reaction enthalpy was determined as ΔH(298)° = -75.6 ± 2.3 kJ mol(-1).