Argon matrix effect on the geometry and infrared spectrum of H2CMH2 (M = Ti, Zr, Hf): A theoretical study

Within the framework of polarizable continuum model with integral equation formalism (IEF-PCM), an argon matrix effect on the geometry and infrared frequencies of the agostic H₂CMH₂ (M = Ti, Zr, Hf) methylidene complexes was investigated at B3LYP level of theory with the 6-311++G(3df,3pd) basis set for C, H, and Ti atoms and Stuttgart/Dresden ECPs MWB28 and MWB60 for the Zr and Hf atoms. At the B3LYP/IEF-PCM level of theory, H₂CTiH₂ was optimized to an energy minimum having a pyramidal structure. The calculated dipole moment of this structure is 3.06 D. The B3LYP/IEF-PCM simulations gave the three complexes’ agostic angle ∠HCM (°), distance r(H?M) (Å), and CM bond length r(CM) (Å) as follows: ∠HCTi = 87.4, r(H?Ti) = 2.079, r(CTi) = 1.803; ∠HCZr = 89.3, r(H?Zr) = 2.243, r(CZr) = 1.956; ∠HCHf = 94.7, r(H?Hf) = 2.343, r(CHf) = 1.972. As a comparison, the B3LYP simulations gave the values as follows: ∠HCTi = 91.5, r(H?Ti) = 2.150, r(CTi) = 1.811; ∠HCZr = 92.9, r(H?Zr) = 2.299, r(CZr) = 1.955; ∠HCHf = 95.6, r(H?Hf) = 2.352, r(CHf) = 1.967. As far as the MH₂ symmetric and asymmetric stretching and CH₂ wagging frequencies are concerned, the IEF-PCM calculated values are in better agreement with the experimental argon matrix ones than those calculated based on a gas phase model.     

Synthesis and characterization of three new fluorovanadate complexes: N(C2H5)4[VOF4], N(CH3)4[VOF3Cl], N(C4H9)4[VOF3Br] and theoretical calculations of VOF4, VOF3Cl and VOF3Br ions

The reaction of VOF₃ with (C₂H₅)₄NF, (CH₃)₄NCl and (C₄H₉)₄NBr salts in anhydrous CH₃CN produced new complexes with the anion general formula [VOF₃X]⁻ in that (X = F⁻, Cl⁻, Br⁻). These were characterized by elemental analysis, IR, UV/Visible and ¹⁹F NMR spectroscopy. The optimized geometries and frequencies of the stationary point are calculated at the B3LYP/6-311G level of theory. Theoretical results showed that the VX (X = F, Cl, Br) bond length values for the [VOF₃X]⁻ in compounds 1-3 are 1.8247, 2.4031 and 2.5595 Å, respectively. Also, the VF₅ bond length values in [VOF₃X]⁻ are 1.824, 1.812 and 1.802 Å, respectively. These results reveal that the bond order for VX bonds decrease from compounds 1 to 3, while for VF₅ bonds, the bond orders increase. It can be concluded that the decrease of VX bonds lengths and the increase of VF₅ bond lengths in compounds 1-3 result from the increase of the hyperconjugation from compounds 1 to 3. Harmonic vibrational frequencies and infrared intensities for VOF₄⁻, VOF₃Cl⁻ and VOF₃Br⁻ are studied by means of theoretical and experimental methods. The calculated frequencies are in reasonable agreement with the experiment values. These data can be used in models of phosphoryl transfer enzymes because vanadate can often bind to phosphoryl transfer enzymes to form a trigonal-bipyramidal structure at the active site.     

Intermolecular hydrogen bonding in the binary mixture [(C2H5)2CO + CH3OH] probed by polarized Raman measurements and DFT calculations

The Raman spectra of neat (C₂H₅)₂CO (pentanone) and its binary mixtures with hydrogen donor solvent (CH₃OH), [(C₂H₅)₂CO + CH₃OH] having different mole fractions of the reference system, (C₂H₅)₂CO in the range 0.1-0.9 at a regular interval of 0.1 were recorded in the CO stretching region. In neat liquid, the Raman peak appears asymmetric. The asymmetric nature of the peak has been attributed to the CO stretching mode of the two conformers of (C₂H₅)₂CO having C₂ and C_2v point groups and the corresponding bands at ∼1711 and ∼1718 cm⁻¹, respectively. A careful analysis of the I_iso (isotropic component of the Raman scattered intensity) at different concentrations reveals that upon dilution with methanol, at mole fraction C = 0.6, an additional peak in the CO stretching region is observed at ∼1703 cm⁻¹ which is attributed to the hydrogen bonding with methanol. A peculiar feature in this study is that upon dilution, the peak at ∼1718 cm⁻¹ shows a minimum at C = 0.6, but on further dilution it shows a blue shift. However, the other peak at ∼1711 cm⁻¹ shows a continuous red shift with dilution as well as a maximum at C = 0.7 in the linewidth vs. concentration plot, which is essentially due to competition between motional narrowing and diffusion phenomena. A significant amount of narrowing in the Raman band at ∼1718 cm⁻¹ can be understood in terms of caging effect of the reference molecule by the solvent molecules at high dilution. A density functional theoretic (DFT) calculation on optimized geometries and vibrational frequencies of two conformers of neat (C₂H₅)₂CO in C₂ ad C_2v forms and the complexes with one and two CH₃OH molecules with both the conformers was performed. The experimental results and theoretical calculations together indicate a co-existence of two conformers as well as hydrogen bonded complex with methanol in the binary mixture, [(C₂H₅)₂CO + CH₃OH] at intermediate concentrations.     

Synthesis, characterization and crystal structures of polymeric and dimeric triphenyltin(IV) complexes of 4-[((E)-1-{2-hydroxy-5-[(E)-2-(2-carboxyphenyl)-1-diazenyl]phenyl}methylidene)amino]aryls

The triphenyltin(IV) complexes of 4-[((E)-1-{2-hydroxy-5-[(E)-2-(2-carboxyphenyl)-1-diazenyl]phenyl}methylidene)amino]aryls (aryls = 4-CH₃, 4-Br, 4-Cl, 4-OCH₃) have been synthesized and characterized by ¹H-, ¹³C-, ¹¹⁹Sn-NMR, ESI mass spectrometry, IR and ^119mSn Mössbauer spectroscopic techniques in combination with elemental analysis. The crystal structures of a representative carboxylate ligand (aryl = 4-CH₃) and three Sn complexes, viz., polymeric (Ph₃Sn[O₂CC₆H₄{NN(C₆H₃-4-OH(C(H)NC₆H₄X-4))}-o])_n (X = Me (1) and Br (2)) and dimeric (Ph₃Sn[O₂CC₆H₄{NN(C₆H₃-4-OH(C(H)NC₆H₄X-4))}-o])₂ (X = OMe (4)) complexes are reported. The coordination environment in each complex is trigonal bipyramidal trans-Ph₃SnO₂. A single zwitterionic carboxylate ligand bridges adjacent Sn atoms via the carboxylate and phenoxide O atoms.     

Effect of substituents on the molybdenum mediated carbonylation and methoxycarbonylation of dihaloalkynes

Dihaloalkynes of the type YCH(R)CCCH(R)Y (Y = Cl, Br, I; R = H or Me) or YCMe₂CCCMe₂Y were prepared from their diol precursors and reacted with [Mo(CO)₃(phen)Y]⁻ (phen = 1,10-phenanthroline) in chlorinated solvent, methanol or water. Formation and stability of substituted products of the type [Mo(CO)₂(η³-CH(R)C(COX)CCH(R))(phen)Y] (X = Y or X = OMe) were found to be dependent upon the nature of the halogen and degree of alkyl substitution of the alkyne. Reactions carried out in mixtures of methanol and ethers gave an alternative double addition product of the type [Mo(CO)₂(η³-CH(R)C(CO₂Me)CC(OMe)(CH₂R))(phen)Y] for R = H, Y = Cl only.     

Zwitterionic diiron vinyliminium complexes: Alkylation, metalation and oxidative coupling at the S and Se functionalities

The zwitterionic vinyliminium complex [Fe₂{μ-η¹:η³-C(R′)C(S)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂] (2a) (R′ = p-Me-C₆H₄ (Tol), Xyl = 2,6-Me₂C₆H₃) undergoes electrophilic addition at the S atom by HSO₃CF₃, MeSO₃CF₃, SiMe₃Cl, BrCH₂Ph, ICH₂CHCH₂ affording the complexes [Fe₂{μ-η¹:η³-C(Tol)C(SX)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂][Y] (X =  H, Y = SO₃CF₃, 4a; X = Me, Y = SO₃CF₃, 4b; X = SiMe₃, Y = Cl, 4c; X = CH₂Ph, Y = Br, 4d; X = CH₂CHCH₂, Y = I, 4e).Compound 2a and the corresponding vinyliminium complexes 2b and 2c (R′ = CH₂OH, 2b; R′ = Me, 2c) react also with etherated BF₃ leading to the formation of the corresponding S-adducts [Fe₂{μ-η¹:η³-C(R′)C(SBF₃)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂] (R′ = Tol, 5a; R′ = CH₂OH, 5b; R′ = Me, 5c).In analogous reactions, the zwitterionic vinyliminium complexes undergo S-metalation upon treatment with in situ generated [Fp]⁺[SO₃CF₃]⁻ [Fp = Fe(CO)₂(Cp)], leading to the formation of [Fe₂{μ-η¹:η³-C(R′)C(S-Fp)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂][SO₃CF₃](R′ = CH₂OH, 6a; R′ = Me, 6b; R′ = Buⁿ, 6c).Similarly, zwitterionic vinyliminium containing Se in the place of S also undergo Se-electrophilic addition. Thus, the complexes [Fe₂{μ-η¹:η³-C(R′)C(SeX)CN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R = X = Me, R′ = Tol, 7a; R = Xyl, R′ = Me, X = Fp⁺, 7b) are obtained upon treatment of the neutral zwitterionic precursors with MeSO₃CF₃ and [Fp][SO₃CF₃], respectively.Alkylation at the S or Se atom of the bridging ligand is also accomplished by CH₂Cl₂, used as solvent, although the reaction is slower compared to more efficient alkylating reagents. The complexes formed by this route are [Fe₂{μ-η¹:η³-C(R′)C(E-CH₂Cl)CN(Me)(R)}(μ-CO)(CO)(Cp)₂][X] [E = S, R = Xyl, R′ = Tol, X = Cl, 8a; E = S, R = Xyl, R′ = Me, X = Cl, 8b; E = Se, R = R′ = Me, X = BPh₄, 8c].Finally, treatment of the zwitterionic vinyliminium complexes with I₂ results in the oxidative coupling with formation of S-S (disulfide) or Se-Se (diselenide) bond. The reactions, performed in the presence of NaBPh₄ afford the tetranuclear complexes [Fe₂{μ-η¹:η³-C(R′)C(E)CN(Me)(R)}(μ-CO)(CO)(Cp)₂]₂[BPh₄]₂ [R = Xyl, R′ = CH₂OH, E = S, 9a; R = Xyl, R′ = Me, E = S, 9b; R = Xyl, R′ = Buⁿ, E = S, 9c; R = Xyl, R′ = Me, E = Se, 9d; R = Me, R′ = Buⁿ, E = Se, 9e].The molecular structures of 4a, 8c and 9e have been determined by X-ray diffraction studies.     

Formation and crystal structures of [(alkoxy)bis(pyridin-2-yl)methanolato-N,O,N]tin(IV) complexes

Reactions of bis(pyridin-2-yl)ketone with tin tetrahalides, SnX₄ (X = Cl or Br), or organotin trichlorides, R^′SnCl₃ (R^′ = Ph, Bu or CH₂CH₂CO₂Me), in ROH (R = Me or Et) readily produces RObis(pyridin-2-yl)methanolato)tin complexes, [5: RO(py)₂C(OSnX₃)] (5: R,X = Me,Cl; Et,Cl; Et,Br) or [6: MeO(py)₂C(OSnCl₂R^′)] (R^′ = Ph, Bu, CH₂CH₂CO₂Me). In addition, halide exchange reaction between SnI₄ and (5: R,X = Me,Cl) occurred to give (5: R,X = Me,I). The crystal structures of six tin(IV) derivatives indicated, in all cases, a monoanionic tridentate ligand, [RO(py)₂C(O⁻)-N,O,N], arranged in a fac manner about a distorted octahedral tin atom. The Sn–O and Sn–N bonds lengths do not show much variation amongst the six complexes despite the differences in the other ligands at tin.     

Syntheses, structures and electrochemistry of some 1-(η-allylamino)-1-ferrocenylcarbene complexes of chromium(0), molybdenum(0) and tungsten(0) : Part 13: The chemistry of metallacyclic alkenylcarbene complexes

The metallacyclic complexes (OC)₄MC(η²-NHCH₂CHCHX)Fc (4; X = H) and (5; X = CH₂OH) [M = Cr: a; Mo: b; W: c; Fc = ferrocenyl = CpFe(C₅H₄)] were obtained in good yields upon photo-decarbonylation of the bimetallic allylaminocarbene complexes (OC)₅MC(NHCH₂CHCHX)Fc (2; X = H)/(3; X = CH₂OH). At room temperature complexes 2/3 exist as mixtures of E- and predominantly Z-isomers with regard to the C-N bond. The molecular structures of 4b and 4c were determined by X-ray diffraction analyses. The intermetallic communicative effects and the interplay of Fc and η²-alkene moieties of 4a and 4b were assessed by cyclovoltammetry. All complexes were also characterized in solution by one- and two-dimensional NMR spectroscopy (¹H, ¹³C, ¹H NOE, ¹H/¹H COSY, ¹³C/¹H HETCOR).     

New developments in the studies of the reactivity of cyclometallated palladium(II) compounds with homo- ([P,P],[As,As]) and heterobidentate ([P,N],[P,O]) ligands

Treatment of the chloro-bridged dinuclear compounds [{Pd[RC₆H₃C(H)NCy-C2,N]}(μ-Cl)]₂ (R = 4-(COH), 1; R = 5-(COH), 2) with bidentate phosphorus or arsenic diphosphines or diarsine ligands in 1:1 molar ratio gave the dinuclear complexes [{Pd[RC₆H₃C(H)NCy-C2,N](Cl)}₂{μ-(o-Tol)₂P(CH₂)₂P(o-Tol)₂}] (R = 4-(COH), 3; R = 5-(COH), 4), [{Pd[RC₆H₃C(H)NCy-C2,N](Cl)}₂{μ-Ph₂PC₄H₂(NH)CH₂PPh₂}] (R = 4-(COH), 5; R = 5-(COH), 6) and [{Pd[RC₆H₃C(H)NCy-C2,N](Cl)}₂{μ-Ph₂As(CH₂)₂AsPh₂}] (R = 4-(COH), 7; R = 5-(COH), 8) with the homobidentate [P,P] and [As,As] ligands in a bridging mode. Treatment of 1 and 2 with the aminophosphine Ph₂P(CH₂)₂NH₂ yields the dinuclear complexes [{Pd[RC₆H₃C(H)NCy-C2,N](Cl)}₂{μ-Ph₂P(CH₂)₂NH₂}] (R = 4-(COH), 9; R = 5-(COH), 10). The analogous reactions carried out in a 1:2 molar ratio, in the presence of NH₄PF₆ or NaClO₄, gave the mononuclear compounds [Pd{RC₆H₃C(H)NCy-C2,N}{(o-Tol)₂P(CH₂)₂P(o-Tol)₂-P,P}][PF₆] (R = 4-(COH), 11; R = 5-(COH), 12), [Pd{RC₆H₃C(H)NCy-C2,N}{Ph₂PC₄H₂(NH)CH₂PPh₂-P,P}][ClO₄] (R = 4-(COH), 13; R = 5-(COH), 14) and [Pd{RC₆H₃C(H)NCy-C2,N}{Ph₂As(CH₂)₂AsPh₂-As,As}][ClO₄](R = 4-(COH), 15; R = 5-(COH), 16), with the [P,P] and [As,As] ligands chelated to the palladium atom.Treatment of 2 with Ph₂P(CH₂)₃NH₂ in a 1:2 molar ratio in acetone in the presence of NH₄PF₆ afforded the mononuclear compound [Pd{5-(COH)C₆H₃C(H)NCy-C2,N}{Ph₂P(CH₂)₃N(Me₂)-P,N}][PF₆], 17, via intermolecular condensation between the aminophosphine and the solvent. Condensation was precluded using toluene as solvent to give [Pd{RC₆H₃C(H)NCy-C2,N}{Ph₂P(CH₂)_nNH₂-P,N}][PF₆], (n = 3, R = 5-(COH), 18; n = 2, R = 4-(COH), 19; n = 2, R = 5-(COH), 20). Treatment of 1 and 2 with Ph₂P(C₆H₄)CHO in a 1:2 molar ratio in the presence of NH₄PF₆ gave the mononuclear complexes [Pd{RC₆H₃C(H)NCy-C2,N}{2-(Ph₂P)C₆H₄CHO-P,O}][PF₆] (R = 4-(COH), 21; R = 5-(COH), 22) with the palladium atom bonded to four different atoms (C, N, P, O) and a chelating [P,O] ligand. The crystal structures of compounds 7, 11, 15 and 21 have been determined by X-ray crystallography.     

The synthesis and single-crystal X-ray structures of palladium(II) and platinum(II) complexes of the difluorovinyl and 1-chloro-2-fluorovinyl-substituted phosphines, PPh2(Z-CFCFH) and PPh2(E-CClCFH)

The coordination chemistry of the fluorovinyl substituted phosphines PPh₂(Z-CFCFH) and PPh₂(E-CClCFH) with K₂MX₄ (M = Pd, Pt; X = Cl, Br, and I) salts has been investigated resulting in the first reported palladium(II) and platinum(II) complexes of phosphines containing partially fluorinated vinyl groups. The complexes have been characterised by a combination of multinuclear [¹H, ¹³C{¹H}, ¹⁹F, ³¹P{¹H}] NMR spectroscopy, and IR/Raman spectroscopy. The single-crystal X-ray structures of trans-[PdX₂{PPh₂(CFCFH)}₂], X = Cl (1), Br (2), I (3), trans-[PdCl₂{PPh₂(CClCFH)}₂] (4), cis-[PtX₂{PPh₂(CFCFH)}₂], X = Cl (5), Br (6), trans-[PtI₂{PPh₂(CFCFH)}₂] (7), and both cis- and trans-[PtCl₂{PPh₂(CClCFH)}₂] (8), have been determined. Results obtained from spectroscopic and crystallographic data suggest that replacement of a β-fluorine by hydrogen, whilst reducing the steric demand of the ligand, has little effect on the electronic character of the ligand. The presence of a proton in the vinyl group results in short proton-halide secondary interactions in the solid state (d(H?X) = 2.72(3) for 1, and 2.92(5) Å for 2) forming an infinite chain ribbon motif.     

Titanium and zirconium ketimide complexes: synthesis and ethylene polymerisation catalysis

The syntheses of ketimide titanium complexes of the type Ti(NC^tBu₂)₃X (X = Cl, Cp, Ind), Ti(NC^tBu₂)₄ and the zirconium complex CpZr(NC^tBu₂)₂Cl are described. When activated by MAO, all compounds are ethylene polymerisation catalysts. In the conditions studied, the most active catalyst is CpZr(NC^tBu₂)₂Cl, with an activity of 2.7 × 10⁵ kg/(molZr [E] h). Titanium complexes are less active by about two orders of magnitude. The polyethylene produced is linear, as determined by NMR spectroscopy. Molecular structures of Ti(NC^tBu₂)₃X (X = Cl, Cp, Ind) and Ti(NC^tBu₂)₄ were determined by X-ray single crystal diffraction.     

Heterometallic Pt-Ag and Pt2Ag transition metal complexes

Complexes of type {cis-[Pt](μ-σ,π-CCPh)₂}AgX (3a, [Pt] = (bipy′)Pt, X = FBF₃; 3b, [Pt] = (bipy′)Pt, X = FPF₅; 3c, [Pt] = (bipy)Pt, X = OClO₃; 3d, [Pt] = (bipy′)Pt, X = BPh₄; bipy′ = 4,4′-dimethyl-2,2′-bipyridine; bipy = 2,2′-bipyridine) are accessible by combining cis-[Pt](CCPh)₂ (1a, [Pt] = (bipy′)Pt; 1b, [Pt] = (bipy)Pt) with equimolar amounts of [AgX] (2a, X = BF₄; 2b, X = PF₆; 2c, X = ClO₄; 2d, X = BPh₄). In 3a-3d the platinum(II) and silver(I) ions are connected by σ- and π-bonded phenyl acetylide ligands. When the molar ratio of 1 and 2 is changed to 2:1 then trimetallic [{cis-[Pt](μ-CCPh)₂}₂Ag]X (8a, [Pt] = (bipy)Pt, X = BF₄; 8b, [Pt] = (bipy′)Pt, X = PF₆; 8c, [Pt] = (bipy)Pt, X = BF₄) is produced. The solid state structure of 8a was determined by single X-ray crystal structure analysis. In 8a the silver(I) ion is embedded between two parallel oriented cis-[Pt](CCPh)₂ units. Within this structural arrangement the phenyl acetylides of individual [Pt](CCPh)₂ entities possess a μ-bridging position between Pt(II) and Ag(I). In addition, a very weak dative Pt → Ag interaction is found (Pt-Ag 2.8965(3) Å). The respective silver carbon distances Ag-C_α (2.548(7), 2.447(7) Å) and Ag-C_β (3.042(7), 2.799(8) Å)(PtC_αC_βPh) confirm this structural motif.Complexes 8a-8c isomerize in solution to form trimetallic [{cis-[Pt](μ-σ,π-CCPh)₂}₂Ag]X (9a, [Pt] = (bipy)Pt, X = BF₄; 9b, [Pt] = (bipy′)Pt, X = PF₆; 9c, [Pt] = (bipy)Pt, X = ClO₄). In the latter molecules the organometallic cation [{cis-[Pt](μ-σ,π- CCPh)₂}₂Ag]⁺ is set-up by two nearly orthogonal positioned [Pt](CCPh)₂ entities which are hold in close proximity by the group-11 metal ion. Within this assembly all four PhCC units are η²-coordinated to silver(I). A possible mechanism for the formation of 9 is presented.     

Alkynyl Ti-M complexes with M = Cd and Hg: Synthesis, characterization, and reaction chemistry

The synthesis and properties of heterobimetallic Ti-Cd complexes of type {[Ti](μ-η¹:η²-CCR)₂}CdX₂ ([Ti] = Ti(η⁵-C₅H₄SiMe₃)₂; R = SiMe₃: 3a, X = Cl; 3b, X = Br; 3c, X = I; R = Fc: 3d, X = Br; Fc = Fe(η⁵-C₅H₄)(η⁵-C₅H₅) is reported. These compounds were accessible by treatment of [Ti](CCR)₂ (1a, R = SiMe₃; 1b, R = Fc) with the cadmium salts CdX₂ (2a, X = Cl; 2b, X = Br; 2c, X = I) in a 1:1 M ratio in diethyl ether. Dissolving, for example, 3b in tetrahydrofuran afforded coordination polymer [Cd(μ-Br)₂(thf)₂]_n (4) along with the tweezer molecule 1a. Treatment of 3b with two equiv of LiCCFc (5) gave {[Ti](μ-η¹:η²-CCSiMe₃)₂}Cd(CCFc)₂ (6) which eliminated at ambient temperature the all-carbon buta-1,3-diyne FcCC-CCFc (7) producing 1a and elemental Cd. The same reaction behavior was observed, when 2b was reacted with 5. The thus obtained bis(alkynyl) cadmium complex Cd(CCFc)₂ (8) is redox-active at low temperature producing 7 and Cd(0). When mercury halides HgX₂ (9a, X = Cl; 9b, X = Br) are used, then the titanocene dihalides [Ti]X₂ (10a, X = Cl; 10b, X = Br) together with Me₃SiCC-CCSiMe₃ (11) and Hg(0) were formed. Nevertheless, mercury acetylides were available by treatment of Hg(OAc)₂ (12) with HCCFc (13) in a 1:2 M ratio. Thus obtained Hg(CCFc)₂ (14) gave with [CuBr] (15) coordination polymer [{Hg(η²-CCFc)₂}(Cu₂(μ-Br)₂]_n (16), while with [AgPF₆] oxidation of the ferrocenyl moieties took place affording dicationic [Hg(CCFc)₂]²⁺ (18).The structures of 3b and 4 in the solid state are reported. Compound 3b shows the typical characteristics for heterobimetallic organometallic π-tweezer complexes with cadmium in a tetrahedral environment, while 4 corresponds to a one-dimensional coordination polymer in which the Cd(II) ions are linked in a edge-sharing fashion by bromide bridges in the pseudo-equatorial plane. The appropriate tetrahydrofuran molecules are completing the pseudo-octahedral coordination sphere at cadmium.The cyclic voltammogram of 14 is reported showing a single reversible redox event at E⁰ = 0.108 V with ΔE_p = 76 mV indicating that there is no communication between the Fc termini along the mercury acetylide unit.     

A promising new catalyst family for enantioselective cycloadditions involving allenes and imines: chiral phosphines with transition metal-CH2-P: linkages

The racemic rhenium-containing phosphine (η⁵-C₅H₅)Re(NO)(PPh₃)(CH₂PPh₃) (3) catalyzes the [3+2] cycloaddition of H₂CCCHCO₂Et and N-tosyl imines ArCHNTs in C₆H₆ (RT, 1 d, 20 mol %) to give 2-aryl-3-carbethoxy-3-pyrrolines (Arp-C₆H₄X (X = H, NO₂, OMe, Me, Cl, Br), 2-furyl; 95-84% isolated). Similar reactions with enantiopure (S)-3 are conducted in C₆H₅Cl at −30 °C (8 d) to maximize enantioselectivities (60-51% ee; 93-90% isolated).     

Theoretical study of the thermochemistry and the kinetics of the SFxCl (x = 0-5) series

A systematic thermodynamic and kinetic study of the entire SF_xCl (x = 0-5) series has been carried out. High-level quantum chemical composite methods have been employed to derive enthalpy of formation values from calculated atomization and isodesmic energies. The resulting values for the SCl, SFCl, SF₂Cl(C₁), SF₃Cl(C_s), SF₄Cl(C_s) and SF₅Cl molecules are 28.0, −36.0, −64.2, −134.3, −158.2 and −237.1 kcal mol⁻¹. A comparison with previous experimental and theoretical values is presented. Statistical adiabatic channel model/classical trajectory, SACM/CT, calculations of selected complex-forming and recombination reactions of F and Cl atoms with radicals of the series have been performed between 200 and 500 K. The reported rate coefficients span over the normal range of about 6 × 10⁻¹² and 5 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ expected for this type of barrierless reactions.     

An antiferromagnetically coupled hexanuclear copper(II) Schiff base complex containing phenoxo and dicyanamido bridges: Structural aspects and magnetic properties

A novel hexanuclear complex [{(CuL)₂Cu}₂(μ-dca)₂](ClO₄)₂·2L′(1) (where H₂L = (OH)C₆H₄C(CH₃)N(CH₂)₃NC(CH₃)C₆H₄(OH) or N,N′-bis(2-hydroxyacetophenone) propylenediimine and dca = N(CN)₂⁻ and L′ = 2-hydroxyacetophenone) has been synthesized and characterized by elemental analysis, UV-Vis, FT-IR spectroscopic and electrochemical methods. Single crystal X-ray structural characterization reveals a centrosymmetric nature of the complex unit, where the metal centers adopt distorted square-planar and distorted octahedral geometries. Structural analysis also reveals μ₂-phenoxo bridges between terminal and the central copper(II) centers of the asymmetric [(CuL)₂Cu(dca)] unit, the latter being interconnected to its symmetry related counterpart by double μ_1,5-dca bridges, leading to the hexanuclear complex ion [{(CuL)₂Cu}₂(μ-dca)₂]²⁺. Low temperature susceptibility measurements of 1 revealed the presence of strong antiferromagnetic coupling (2J = −407 cm⁻¹) between the copper(II) centers.