Mechanistic investigation of vinylic carbon-fluorine bond activation of perfluorinated cycloalkenes using Cp*2ZrH2 and Cp*2ZrHF

Cp*₂ZrH₂ (1) (Cp*: pentamethylcyclopentadienyl) reacts with cyclic perfluorinated olefins to give Cp*₂ZrHF (2) and hydrodefluorinated products under very mild conditions. Initial C-F bond activation occurs selectively at the vinylic positions of the cycloolefin to exchange fluorine for hydrogen. Several mechanisms are discussed for this H/F exchange: (a) olefin insertion/β-fluoride elimination, (b) olefin insertion/α-fluoride elimination, and (c) hydride/fluoride σ-bond metathesis. Following H/F σ-bond metathesis exchange of both vinylic C-F bonds of perfluorocyclobutene, 1 then reacts with allylic C-F bonds by insertion/β-fluoride elimination. A similar sequence is observed with perfluorocyclopentene. Cp*₂ZrHF reacts selectively with vinylic C-F bonds of perfluorocyclobutene to give 3,3,4,4-tetrafluorocyclobutene and Cp*₂ZrF₂ without further hydrodefluorination occurring. In the presence of excess 1 and H₂, perfluorocyclobutene and perfluorocyclopentene are reduced to cyclobutane and cyclopentane in 46% and 16% yield, respectively. DFT calculations exclude the pathway by way of the olefin insertion/α-fluoride elimination and suggest that the pathway by way of hydride/fluoride σ-bond metathesis is preferred.     

Quantum chemical study of ethylene addition to group-7 oxo complexes MO2(CH3)(CH2) (M = Mn, Tc, Re)

Quantum chemical calculations using DFT at the B3LYP level have been carried out for the reaction of ethylene with the group-7 compounds ReO₂(CH₃)(CH₂) (Re1), TcO₂(CH₃)(CH₂) (Tc1) and MnO₂(CH₃)(CH₂) (Mn1). The calculations suggest rather complex scenarios with numerous pathways, where the initial compounds Re1-Mn1 may either engage in cycloaddition reactions or numerous addition reactions with concomitant hydrogen migration. There are also energetically low-lying rearrangements of the starting compounds to isomers which may react with ethylene yielding further products. The [2 + 2]_Re,C cycloaddition reaction of the starting molecule Re1 is kinetically and thermodynamically favored over the [3 + 2]_C,O and [3 + 2]_O,O cycloadditions. However, the reaction which leads to the most stable product takes place with initial rearrangement to the dioxohydridometallacyclopropane isomer Re1a that adds ethylene with concomitant hydrogen migration yielding Re1a-1. The latter reaction has a slightly higher barrier than the [2 + 2]_Re,C cycloaddition reaction. The direct [3 + 2]_C,O cycloaddition becomes more favorable than the [2 + 2]_M,C reaction for the starting compounds Tc1 and Mn1 of the lighter metals technetium and manganese but the calculations predict that other reactions are kinetically and thermodynamically more favorable than the cycloadditions. The reactions with the lowest activation barriers lead after rearrangement to the ethyl substituted dioxometallacyclopropanes Tc1a-1 and Mn1a-1. The manganese compound exhibits an even more complex reaction scenario than the technetium compounds. The thermodynamically most stable final product of ethylene addition to Mn1 is the ethoxy substituted metallacyclopropane Mn1a-2 which has, however, a high activation barrier.     

Synthesis, structural characterization and reactivity of new tin bridged ansa-bis(cyclopentadiene) compounds: X-ray crystal structures of Me2Sn(C5Me4R-1)2 (R = H, SiMe3)

The organo-tin compounds, Me₂Sn(C₅H₄R-1)₂ (R = Me (1), Prⁱ (2), Bu^t (3), SiMe₃ (4)) and Me₂Sn(C₅Me₄R-1)₂ (R = H (5), SiMe₃ (6)), were prepared by the reaction of Me₂SnCl₂ with the lithium or sodium derivative of the corresponding cyclopentadiene. Compounds 1-6 have been characterized by multinuclear NMR spectroscopy (¹H, ¹³C, ¹¹⁹Sn). In addition the molecular structures of 5 and 6 were determined by single crystal X-ray diffraction studies. The transmetalation reaction of 1-6 with ZrCl₄ or [NbCl₄(THF)₂] gave the corresponding metallocene complexes in high yields.     

Synthesis and characterisation of six Fe(II or III), Co(II) or Zr(IV) complexes containing the ligand [CH(SiMe2R)P(Ph)2NSiMe3] (R = Me, NEt2) and of [Co{N(SiMe3)C(Ph)C(H)P(Ph)2NSiMe3}2]

The C,N-(trimethylsilyliminodiphenylphosphoranyl)silylmethylmetal complexes [Fe(L)₂] (3), [Co(L)₂] (4), [ZrCl₃(L)]·0.83CH₂Cl₂ (5), [Fe(L)₃] (6), [Fe(L′)₂] (7) and [Co(L′)₂] (8) have been prepared from the lithium compound Li[CH(SiMe₂R)P(Ph)₂NSiMe₃] [1a, (R = Me) {≡ Li(L)}; 1b, (R = NEt₂) {≡ Li(L′)}] and the appropriate metal chloride (or for 7, FeCl₃). From Li[N(SiMe₃)C(Ph)C(H)P(Ph)₂NSiMe₃] [≡ Li(L″)] (2), prepared in situ from Li(L) (1a) and PhCN, and CoCl₂ there was obtained bis(3-trimethylsilylimino- diphenylphosphoranyl-2-phenyl-N-trimethylsilyl-1-azaallyl-N,N′)cobalt(II) (9). These crystalline complexes 3-9 were characterised by their mass spectra, microanalyses, high spin magnetic moments (not 5) and for 5 multinuclear NMR solution spectra. The X-ray structure of 3 showed it to be a pseudotetrahedral bis(chelate), the iron atom at the spiro junction.     

Reactivity of 2,3-bis(2-pyridyl)pyrazine with [Re2(CO)8(CH3CN)2]: Molecular structures of [Re2(CO)8(C14H10N4)] and [Re2(CO)8(C14H10N4)Re2(CO)8]

The reaction of the labile compound [Re₂(CO)₈(CH₃CN)₂] with 2,3-bis(2-pyridyl)pyrazine in dichloromethane solution at reflux temperature afforded the structural dirhenium isomers [Re₂(CO)₈(C₁₄H₁₀N₄)] (1 and 2), and the complex [Re₂(CO)₈(C₁₄H₁₀N₄)Re₂(CO)₈] (3). In 1, the ligand is σ,σ′-N,N′-coordinated to a Re(CO)₃ fragment through pyridine and pyrazine to form a five-membered chelate ring. A seven-membered ring is obtained for isomer 2 by N-coordination of the 2-pyridyl groups while the pyrazine ring remains uncoordinated. For 2, isomers 2a and 2b are found in a dynamic equilibrium ratio [2a]/[2b]  =  7 in solution, detected by ¹H NMR (−50 °C, CD₃COCD₃), coalescence being observed above room temperature. The ligand in 3 behaves as an 8e-donor bridge bonding two Re(CO)₃ fragments through two (σ,σ′-N,N′) interactions. When the reaction was carried out in refluxing tetrahydrofuran, complex [Re₂(CO)₆(C₁₄H₁₀N₄)₂] (4) was obtained in addition to compounds 1-3. The dinuclear rhenium derivative 4 contains two units of the organic ligand σ,σ′-N,N′-coordinated in a chelate form to each rhenium core. The X-ray crystal structures for 1 and 3 are reported.     

Synthesis and characterization of hetero-binuclear Co-Rh complexes [CpCoS2C2(B9H10)][Rh(COD)] and [CpCoSe2C2(B10H10)][Rh(COD)]

Two hetero-binuclear complexes [Cp^∗CoS₂C₂(B₉H₁₀)][Rh(COD)] (2a) and [Cp^∗CoSe₂C₂(B₁₀H₁₀)][Rh(COD)] (2b) [Cp^∗ = η⁵-pentamethylcyclopentadienyl, COD = cyclo-octa-1,5-diene (C₈H₁₂)] were synthesized by the reactions of half-sandwich complexes [Cp^∗CoE₂C₂(B₁₀H₁₀)] [E = S (1a), Se (1b)] with low valent transition metal complexes [Rh(COD)(OEt)]₂ and [Rh(COD)(OMe)]₂. Although the reaction conditions are the same, the structures of two products for dithiolato carborane and diselenolato carborane are different. The cage of the carborane in 2a was opened; However, the carborane cage in 2b was intact. Complexes 2a and 2b have been fully characterized by ¹H, ¹¹B NMR and IR spectroscopy, as well as by elemental analyses. The molecular structures of 2a and 2b have been determined by single-crystal X-ray diffraction analyses and strong metal-metal interactions between cobalt and rhodium atoms (2.6260 Å (2a) and 2.7057 Å (2b)) are existent.     

Monomeric and dimeric ruthenium thiooxalate complexes: Structures of CpRu(PPh3)2SCOCO2Me and CpRu(dppe)SCOCO2Et

The hydrosulfido complexes CpRu(L)(L′)SH react with one equivalent of O-alkyl oxalyl chlorides (ROCOCOCl) to form the corresponding O-alkylthiooxalate complexes CpRu(L)(L′)SCOCO₂R (L = L′ = PPh₃ (1), (2); L = PPh₃, L′ = CO (3); R = Me (a), Et (b)). The reactions of the hydrosulfido complexes with half equivalent of oxalyl chloride produce the bimetallic complexes [CpRu(L)(L′)SCO]₂ (L = L′ = PPh₃ (4), (5); L = PPh₃, L′ = CO (6)). The crystal structures of CpRu(PPh₃)₂SCOCO₂Me (1a) and CpRu(dppe)SCOCO₂Et (2b) are reported.     

Reactivity of M(en)Cl2 (M = Pd/Pt,en = 1,2-diaminoethane) with N,N′-bis(salicylidene)-p-phenylenediamine: Binding with hexafluorobenzene

Schiff base N,N′-bis(salicylidene)-p-phenylenediamine (LH₂) complexed with Pt(en)Cl₂ and Pd(en)Cl₂ provided [Pt(en)L]₂ · 4PF₆ (1) and Pd(Salen) (2) (Salen = N,N′-bis(salicylidene)-ethylenediamine), respectively, which were characterized by their elemental analysis, spectroscopic data and X-ray data. A solid complex obtained by the reaction of hexafluorobenzene (hfb) with the representative complex 1 has been isolated and characterized as 3 (1 · hfb) using UV–Vis, NMR (¹H, ¹³C and ¹⁹F) data. A solid complex of hfb with a reported Zn-cyclophane 4 has also been prepared and characterized 5 (4 · hfb) for comparison with complex 3. The association of hfb with 1 and 4 has also been monitored using UV–Vis and luminescence data.     

Formation and skeletal transformations of perfluoroindan-1-one and perfluoroindan-1,3-dione in the reaction of perfluoroindan with SiO2/SbF5

Perfluoroindan-1-one (2) is obtained in the reaction of perfluoroindan (1) with SiO₂/SbF₅ at 70 °C. Compound 1 heated with SiO₂/SbF₅ at 130 °C and then treated with water, gives 3-hydroxy-perfluoro-3-methylphthalide (4). Ketone 2 is converted, under the action of SbF₅ at 130 °C, to perfluoro-2-ethylbenzoic acid (9) and disproportionates to compound 1 and perfluoroindan-1,3-dione (3); the latter is transformed to phthalide 4 under the reaction conditions.     

New effective reagent [Cp2ZrH2 · ClAlEt2]2 for alkene hydrometallation

New bimetallic complex [Cp₂ZrH₂ · ClAlEt₂]₂ (1) was synthesized, and its reactivity in hydrometallation reaction with the following alkenes was studied: hept-1-ene, okt-1-ene, α-methylstyrene, (1S)-β-pinene, (+)-camphene. Complex 1 shows the highest reactivity among the other known Al,Zr-bimetallic complexes: [Cp₂ZrH₂ · ClAlBuⁱ₂]₂ (2), [Cp₂ZrH₂ · AlEt₃]₂ (3), [Cp₂ZrH₂ · AlBuⁱ₃]₂ (4) and [Cp₂ZrH₂ · HAlBuⁱ₂] (5) as well as organoaluminium compounds (OAC): ⁱBu₂AlH, ⁱBu₃Al and ⁱBu₂AlCl in presence of Zr catalysts. Chlorine containing complexes 1 and 2 appear to be more effective in alkene hydrometallation, and relative hydrometallation rates are (1S)-β-pinene ? (+)-camphene < α-methylstyrene < oct-1-ene < hept-1-ene. Hydrometallation of (1S)-β-pinene and its subsequent oxidation with I₂ run with high diastereoselectivity and yield trans-myrtanol. However, the diastereoselectivity of (+)-camphene hydrometallation is less than that for (1S)-β-pinene, and the reaction gives predominately endo-camphanol.     

Reactions of Mo(II)-tetraphosphine complex [MoCl2{meso-o-C6H4(PPhCH2CH2PPh2)2}] with a series of small molecules

Reactions of Mo(II)-tetraphosphine complex [MoCl₂(κ⁴-P4)] (2; P4 = meso-o-C₆H₄(PPhCH₂CH₂PPh₂)₂) with a series of small molecules have been investigated. Thus, treatment of 2 with alkynes RCCR′ (R = Ph, R′ = H; R = p-tolyl, R′ = H; R = Me, R′ = Ph) in benzene or toluene gave neutral mono(alkyne) complexes [MoCl₂(RCCR′)(κ³-P4)] containing tridentate P4 ligand, which were converted to cationic complexes [MoCl(RCCR′)(κ⁴-P4)]Cl having tetradentate P4 ligand upon dissolution into CDCl₃ or CD₂Cl₂. The latter complexes were available directly from the reactions of 2 with the alkynes in CH₂Cl₂. On the other hand, treatment of 2 with 1 equiv. of XyNC (Xy = 2,6-Me₂C₆H₃) afforded a seven-coordinate mono(isocyanide) complex [MoCl₂(XyNC)(κ⁴-P4)] (7), which reacted further with XyNC to give a cationic bis(isocyanide) complex [MoCl(XyNC)₂(κ⁴-P4)]Cl (8). From the reaction of 2 with CO, a mono(carbonyl) complex [MoCl₂(CO)(κ⁴-P4)] (9) was obtained as a sole isolable product. Reaction of 9 with XyNC afforded [MoCl(CO)(XyNC)(κ⁴-P4)]Cl (10a) having a pentagonal-bipyramidal geometry with axial CO and XyNC ligands, whereas that of 7 with CO resulted in the formation of a mixture of 10a and its isomer 10b containing axial CO and Cl ligands. Structures of 7 and 9 as well as [MoCl(XyNC)₂(κ⁴-P4)][PF₆](8′) and [MoCl(CO)(XyNC)(κ⁴-P4)][PF₆] (10a′) derived by the anion metathesis from 8 and 10a, respectively, were determined in detail by the X-ray crystallography.     

Quantum chemistry studies on the Ru-M interactions and the P NMR in [Ru(CO)3(Ph2Ppy)2(MCl2)] (M = Zn, Cd, Hg)

To study the Ru-M interactions and their effects on ³¹P NMR, complexes [Ru(CO)₃(Ph₂Ppy)₂] (py = pyridine) (1) and [Ru(CO)₃(Ph₂Ppy)₂MCl₂] (M = Zn, 2; Cd, 3; Hg, 4) were calculated by density functional theory (DFT) PBE0 method. Moreover, the PBE0-GIAO method was employed to calculate the ³¹P chemical shifts in complexes. The calculated ³¹P chemical shifts in 1-3 follow 2 > 3 > 1 which are consistent to experimental results, proving that PBE0-GIAO method adopted in this study is reasonable. This method is employed to predict the ³¹P chemical shift in designed complex 4. Compared with 1, the ³¹P chemical shifts in 2-4 vary resulting from adjacent Ru-M interactions. The Ru → M or Ru ← M charge-transfer interactions in 2-4 are revealed by second-order perturbation theory. The strength order of Ru → M interactions is the same as that of the P-Ru → M delocalization with Zn > Cd > Hg, which coincides with the order of ³¹P NMR chemical shifts. The interaction of Ru → M, corresponding to the delocalization from 4d orbital of Ru to s valence orbital of M²⁺, results in the delocalization of P-Ru → M, which decreases the electron density of P nucleus and causes the downfield ³¹P chemical shifts. Except 2, the back-donation effect of Ru ← M, arising from the delocalization from s valence orbital of M²⁺ to the valence orbital of Ru, is against the P-Ru → M delocalization and results in the upfield ³¹P chemical shifts in 4. Meanwhile, the binding energies indicate that complex 4 is stable and can be synthesized experimentally. However, as complex [Ru(CO)₃(Ph₂Ppy)₂HgCl]⁺5 is more stable than 4, the reaction of 1 with HgCl₂ only gave 5 experimentally.     

Chemically modified oximato complexes of titanium(IV) isopropoxide as new precursors for the sol-gel preparation of nano-sized titania: Crystal and molecular structure of [Ti{ONC10H16}4·2CH2Cl2]

Reactions of [Ti(OPrⁱ)₄] with various oximes, in anhydrous refluxing benzene yielded complexes of the type [Ti{OPrⁱ}_4−n{L}_n], where, n = 1-4 and LH = (CH₃)₂CNOH (1-4), C₉H₁₆CNOH (5-8) and C₉H₁₈CNOH (9-12). The compounds were characterized by elemental analyses, molecular weight measurements, FAB-mass, FT-IR and NMR (¹H, ¹³C{¹H}) spectral studies. The FAB-mass spectra of mono- (1), and di- (2), (6), (10) substituted products indicate their dimeric nature and that of tri- (3) and tetra- (4), (8) substituted derivatives suggest their monomeric nature. Crystal and molecular structure of [Ti{ONC₁₀H₁₆}₄·2CH₂Cl₂] (8A) suggests that the oximato ligands bind the metal in a dihapto η²-(N, O) manner, leading to the formation of an eight coordinated species. Thermogravimetric curves of (3), (6) and (10) exhibit multi-step decomposition with the formation of TiO₂ as the final product in each case, at 900 °C. Low temperature (∼600 °C) sol-gel transformations of (2), (3), (4), (6), (7) and (8) yielded nano-sized titania (a), (b), (c), (d), (e) and (f), respectively. Formation of anatase phase in all the titania samples was confirmed by powder XRD patterns, FT-IR and Raman spectroscopy. SEM images of (a), (b), (c), (d), (e) and (f) exhibit formation of nano-grains with agglomer like surface morphologies. Compositions of all the titania samples were investigated by EDX analyses. The absorption spectra of the two representative samples, (a) and (f) indicate an energy band gap of 3.17 eV and 3.75 eV, respectively.     

Formation and sigmatropic rearrangement of PhCOC(NO2)CH2 cycloadducts of 1,3-cyclohexadiene: a theoretical study

Competing cycloaddition pathways for the reaction of 2-nitro-1-phenyl-2-propen-1-one with 1,3-cyclohexadiene were investigated employing computational methods. A bifurcating pathway was found for formation of nitroketone 3 and nitronic ester 5. A second bifurcating pathway was found for the formation of nitroketone 4 and enol ether 6. Sigmatropic rearrangements of two cycloadducts, nitronic ester 5 and enol ether 6, were also studied computationally. The reaction pathways were mapped using the B3-LYP/6-311G(d) method and relative energies for species 3-6 were calculated at the same level. Solution-phase corrections were performed by the PCM method. The calculations for both bifurcating cycloaddition pathways indicate kinetic control with similar rate-determining activation energies. The nitroketone 3 is more stable than nitronic ester 5 by 5.3 kcal/mol and nitroketone 4 is more stable than enol ether 6 by 3.9 kcal/mol, consistent with the observed direction of sigmatropic rearrangement.     

Synthesis, characterization and Schlenk equilibrium studies of methylmagnesium compounds with O- and N-donor ligands - the unexpected behavior of [MgMeBr(pmdta)] (pmdta = N,N,N′,N″,N″-pentamethyldiethylenetriamine)

MgMe₂ (1) was found to react with 1,4-diazabicyclo[2.2.2]octane (dabco) in tetrahydrofuran (thf) yielding a binuclear complex [{MgMe₂(thf)}₂(μ-dabco)] (2). Furthermore, from reactions of MgMeBr with diglyme (diethylene glycol dimethyl ether), NEt₃, and tmeda (N,N,N′,N′-tetramethylethylenediamine) in etheral solvents compounds MgMeBr(L), (L = diglyme (5); NEt₃ (6); tmeda (7)) were obtained as highly air- and moisture-sensitive white powders. From a thf solution of 7 crystals of [MgMeBr(thf)(tmeda)] (8) were obtained. Reactions of MgMeBr with pmdta (N,N,N′,N″,N″-pentamethyldiethylenetriamine) in thf resulted in formation of [MgMeBr(pmdta)] (9) in nearly quantitative yield. On the other hand, the same reaction in diethyl ether gave MgMeBr(pmdta) · MgBr₂(pmdta) (10) and [{MgMe₂(pmdta)}₇{MgMeBr(pmdta)}] (11) in 24% and 2% yield, respectively, as well as [MgMe₂(pmdta)] (12) as colorless needle-like crystals in about 26% yield. The synthesized methylmagnesium compounds were characterized by microanalysis and ¹H and ¹³C NMR spectroscopy. The coordination-induced shifts of the ¹H and ¹³C nuclei of the ligands are small; the largest ones were found in the tmeda and pmdta complexes. Single-crystal X-ray diffraction analyses revealed in 2 a tetrahedral environment of the Mg atoms with a bridging dabco ligand and in 8 a trigonal-bipyramidal coordination of the Mg atom. The single-crystal X-ray diffraction analyses of [MgMe₂(pmdta)] (12) and [MgBr₂(pmdta)] (13) showed them to be monomeric with five-coordinate Mg atoms. The square-pyramidal coordination polyhedra are built up of three N and two C atoms in 12 and three N and two Br atoms in 13. The apical positions are occupied by methyl and bromo ligands, respectively. Temperature-dependent ¹H NMR spectroscopic measurements (from 27 to −80 °C) of methylmagnesium bromide complexes MgMeBr(L) (L = thf (4); diglyme (5); NEt₃ (6); tmeda (7)) in thf-d₈ solutions indicated that the deeper the temperature the more the Schlenk equilibria are shifted to the dimethylmagnesium/dibromomagnesium species. Furthermore, at −80 °C the dimethylmagnesium compounds are predominant in the solutions of Grignard compounds 4-6 whereas in the case of the tmeda complex7 the equilibrium constant was roughly estimated to be 0.25. In contrast, [MgMeBr(pmdta)] (9) in thf-d₈ revealed no dismutation into [MgMe₂(pmdta)] (12) and [MgBr₂(pmdta)] (13) even up to −100 °C. In accordance with this unexpected behavior, 1:1 mixtures of 12 and 13 were found to react in thf at room temperature yielding quantitatively the corresponding Grignard compound 9. Moreover, the structures of [MgMeBr(pmdta)] (9c), [MgMe₂(pmdta)] (12c), and [MgBr₂(pmdta)] (13c) were calculated on the DFT level of theory. The calculated structures 12c and 13c are in a good agreement with the experimentally observed structures 12 and 13. The equilibrium constant of the Schlenk equilibrium (2 9c ? 12c + 13c) was calculated to be K_gas = 2.0 × 10⁻³ (298 K) in the gas phase. Considering the solvent effects of both thf and diethyl ether using a polarized continuum model (PCM) the corresponding equilibrium constants were calculated to be K_thf = 1.2 × 10⁻³ and K_ether = 3.2 × 10⁻³ (298 K), respectively.     

Oxime-substituted NCN-pincer palladium and platinum halide polymers through non-covalent hydrogen bonding (NCN = [C6H2(CH2NMe2)2-2,6])

The oxime-substituted NCN-pincer molecules HONCH-1-C₆H₃(CH₂NMe₂)₂-3,5 (2a) and HONCH-4-C₆H₂(CH₂NMe₂)₂-2,6-Br-1 (2b) were accessible by treatment of the benzaldehydes H(O)C-4-C₆H₃(CH₂NMe₂)₂-3,5 (1a) and H(O)C-4-C₆H₂(CH₂NMe₂)₂-2,6-Br-1 (1b) with an excess of hydroxylamine. In the solid state both compounds are forming polymers with intermolecular O-H?N connectivities between the Me₂NCH₂ substituents and the oxime entity of further molecules of 2a and 2b, respectively. Characteristic for 2a and 2b is a helically arrangement involving a crystallographic 2₁ screw axis of the HONCH-1-C₆H₃(CH₂NMe₂)₂-3,5 and HONCH-4-C₆H₂(CH₂NMe₂)₂-2,6-Br-1 building blocks.The reaction of 2b with equimolar amounts of [Pd₂(dba)₃ · CHCl₃] (3) (dba = dibenzylidene acetone) or [Pt(tol)₂(SEt₂)]₂ (4) (tol = 4-tolyl) gave by an oxidative addition of the C-Br unit to M coordination polymers with a [(HONCH-4-C₆H₂(CH₂NMe₂)₂-2,6)MBr] repeating unit (5: M = Pd, 6: M = Pt). Complexes 5 and 6 are in the solid state linear hydrogen-bridged polymers with O-H?Br contacts between the oxime entities and the metal-bonded bromide.     

Si-C coupling reaction of polychloromethanes with HSiCl3 in the presence of Bu4PCl: Convenient synthetic method for bis(chlorosilyl)methanes

Coupling reaction of polychloromethanes CH_4−nCl_n (n = 2-4) with HSiCl₃ in the presence of tetrabutylphosphonium chloride (Bu₄PCl) as a catalyst occurred at temperatures ranging from 30 °C to 150 °C. The reactivity of polychloromethanes increases as the number of chlorine-substituents on the carbon increases. In the reactions of CCl₄ with HSiCl₃, a variety of coupling products such as bis(chlorosilyl)methanes CH₂(SiCl₃)(SiXCl₂) [X = Cl (1a), H (1b)], (chlorosilyl)trichloromthanes Cl₃CSiXCl₂ [X = Cl (2a), H (2b)], and (chlorosilyl)dichloromthanes Cl₂HCSiXCl₂ [X = Cl (3a), H (3b)] were obtained along with reductive dechlorination products such as CHCl₃ and CH₂Cl₂ depending on the reaction temperature. In the reaction of CCl₄, 2a is formed at the initial stage of the coupling reaction and converted to give CHCl₃ at low temperature of 30 °C, to give 1a, 3a, and CHCl₃ at 60 °C, and to afford 1a as major product and CH₂Cl₂ in competition above 100 °C. Si-H bond containing silylmethanes can be formed by the H-Cl exchange reaction with HSiCl₃. Reaction of CHCl₃ with HSiCl₃ took placed at 80 °C to give three compounds 1a, 3a, and CH₂Cl₂, and finally 3a was converted to give 1a and CH₂Cl₂ at longer reaction time. While the condition for the reaction of CH₂Cl₂ with HSiCl₃ required a much higher temperature of 150 °C. Under the optimized conditions for synthesizing bis(chlorosilyl)methanes 1a,b, a mixture of 1a and 1b were obtained as major products in 65% (1a:1b = 64:1) and 47% (42:5) yields from the reaction of CCl₄ and CHCl₃ at 100 °C for 8 h, respectively, and in 41% (34:7) yield from that of CH₂Cl₂ at 170 °C for 12 h. In the Si-C coupling reaction of polychloromethanes with HSiCl₃, it seems likely that a trichlorosilyl anion generated from the reaction of HSiCl₃ with Bu₄PCl is an important key intermediate.     

4,5-Bis[(triorganotin)thiolato]-1,3-dithiole-2-thione, (R3Sn)2(dmit), 4,5-bis[(triorganotin)thiolato]-1,3-dithiole-2-one, (R3Sn)2(dmio), compounds: Crystal structures of (cyclohexyl3Sn)2(dmio), (Ph3Sn)2(dmit) and (Ph3Sn)2(dmio)

The synthesis and crystal structures of 4,5-bis[(triorganotin)thiolato]-1,3-dithiole-2-thione, (R₃Sn)₂(dmit), 1, and 4,5-bis[(triorganotin)thiolato]-1,3-dithiole-2-one, (R₃Sn)₂(dmio), 2, compounds are reported. Compounds, (1 or 2: R = Ph or cyclohexyl, Cy), have been obtained from reaction of R₃SnCl with Cs₂dmit or Na₂dmio. The presence of the two tin centres in (2: R = Ph) is shown in the ¹³C NMR spectrum by the couplings of both Sn atoms to the dmio olefinic carbons with J values of 29.4 and 24.7 Hz. The δ¹¹⁹ Sn values for (1: R = Ph) and (2: R = Ph) differ by about 30 ppm, values being −20.7 and −50.1 ppm, respectively, in CDCl₃ solution. X-ray structure determinations for (1: R = Ph) and (2: R = Ph or Cy) reveal the compounds to have 4-coordinate, distorted tetrahedral tin centres. The dithiolato ligands, dmit and dmio, act as bridging ligands, in contrast to their chelating roles in R₂Sn(dmit) and R₂Sn(dmio). A further difference between R₂Sn(dmit) and R₂Sn(dmio), on one hand, and 1 and 2 on the other, is that intermolecular Sn-S and Sn-O interactions are absent in 1 and 2. However, weak intermolecular hydrogen bonding interactions are found in (1: R = Ph) [C-H?π] and in (2: R = Ph) [C-H?π and C-H?O].     

Synthesis and characterization of scandium complexes with reduced ligands: Crystal structures of Cp∗ScI2, [Cp∗ScI(bpy)]2, and [Cp∗ScCl(bpy)]2

The synthesis and characterization of complexes containing a Cp∗Sc(R₂bpy) (Cp∗ = pentamethylcyclopentadienyl, bpy = 4,4′-R,R-2,2′-bipyridine, R = H, Me) motif are described. Cp∗ScI₂ (1) was prepared from Cp∗Sc(acac)₂ (acac = acetylacetonate) and AlI₃ (2 equiv) in pentane. Compound 1 reacted with bipyridine and 4,4′-dimethyl-2,2′-bipyridine (dmb) in benzene to yield Cp∗ScI₂(bpy) (3) and Cp∗ScI₂(dmb) (4), respectively. Compound 3 was reduced by alkali metal reductants such as Na/Hg, NaK₂, and K in aromatic solvents to yield [Cp∗ScI(bpy)]₂ (5). The chloride analog of 5, [Cp∗ScCl(bpy)]₂ (7), was prepared from Cp∗ScCl₂ by salt metathesis with Li₂(dme)₂bpy (6) (dme = dimethoxyethane) in toluene. Compounds 1, 5, and 7 have been structurally characterized. Analysis of the bond distances of the bipyridine ligands in 5 and 7, together with infrared and UV/vis spectroscopic data, suggest that the bipyridine ligands in these molecules exist as radical anions. The bipyridine ligands in 5 and 7 are arranged co-facially and are in close proximity (?3.30 Å), suggesting the presence of a π-π interaction.     

Syntheses, crystal structures and luminescent properties of two novel lanthanide/4-pya complexes: [Ln(4-pya)3(H2O)2]2 (Ln = Eu, La; 4-pya = trans-4-pyridylacrylate)

Reactions of Ln₂O₃ and trans-4-pyridylacrylic acid (4-Hpya) in EtOH/H₂O or MeOH/H₂O produced two new lanthanide/4-pya complexes [Ln(4-pya)₃(H₂O)₂]₂ (1: Ln = Eu; 2: Ln = La) in low yields. However, reactions of LnCl₃ · 6H₂O with 4-Hpya/aqueous ammonia in EtOH/H₂O or MeOH/H₂O gave rise to 1 or 2 in higher yields. Both compounds were structurally characterized by elemental analysis, IR spectroscopy and X-ray analysis. Compounds 1 · 2EtOH · 2H₂O and 2 · 2MeOH · 2H₂O were confirmed to possess one-dimensional polymeric chain structures. In the structure of 1, each Eu(III) adopts a monocapped square-antiprism coordination geometry and each dimer [Eu(4-pya)₃(H₂O)₂]₂ within the chain is interconnected by two pairs of different bridging 4-pya ligands. On the other hand, each La(III) of 2 takes a bicapped square-antiprism coordination geometry and each dimer [La(4-pya)₃(H₂O)₂]₂ within the chain is linked by two pairs of tridentate bridging 4-pya ligands. The luminescent properties of 1 and 2 in the solid state were investigated.