Iron Catalysis of SO2 Oxidation in the Atmosphere

The mechanisms of SO₂ oxidation catalyzed by iron ions in the droplet phase of the convective cloud in the lower atmosphere were examined. The relations of the catalytic SO₂ decrease to the concentration of the iron ions and to the intensity of fluxes to the droplet of the OH _(g) and HO _2(g) radicals were characterized. The determining role of the replacement of the low-reactive HO _2(g)(O^– _2(aq)) radical by the reactive SO^– _5(aq) radical in the sulfite medium during daytime was revealed. This process occurred due to the coupling of the decay of the radicals and their regeneration in the liquid-phase reactions O^– _2(aq) + FeOH²⁺ _(aq) Fe²⁺ _(aq) + OH^– _(aq) + O_2(aq), HSO^– _5(aq) + Fe²⁺ _(aq) FeOH²⁺ _(aq) + SO^– _4(aq)HSO ₃ ^- _(aq),O_{2 (aq)} SO^– _5(aq).     

Activation of C-H and C-Br bonds in cyclopalladation reactions of Schiff base ligands: Influence of the benzylidene ring substituents

Reaction of Pd(AcO)₂ with the Schiff base ligands 2-Br-4,5-(OCH₂O)C₆H₂C(H)N(Cy) (a) and 4,5-(OCH₂CH₂)C₆H₃C(H)N(Cy) (b) leads to the cyclometallated compounds [Pd{2-Br-4,5-(OCH₂O)C₆HC(H)N(Cy)-C6,N}(μ-O₂CMe)]₂ (1a) and [Pd{4,5-(OCH₂CH₂)C₆H₂C(H)N(Cy)-C6,N}(μ-O₂CMe)]₂ (1b), respectively, via C-H activation. Treatment of a with Pd₂(dba)₃ gave [Pd{4,5-(OCH₂O)C₆H₂C(H)N(Cy)-C2,N}(μ-Br)]₂ (6a), via C-Br activation. The metathesis reaction of 1a and 1b with aqueous sodium chloride gave the corresponding cyclopalladated dimers with bridging chloride ligands, 2a and 2b, respectively. Treatment of the halogen-bridged compounds with tertiary tri- and diphosphines in the appropriate molar ratio gave the mono and dinuclear compounds 3a-5a, 7a-9a and 3b-5b. The structure of compounds 3a, 4a, 5a, 8a, 2b, 3b and 5b has been determined by X-ray diffraction analysis.     

Ferrole-type compounds containing thiophenic or thiepinic rings in the 3,4-positions of the metallacycle

The new ferrole Fe₂(CO)₆[μ-η²,η⁴-(Fc)CC{C(H)C(R)S}CC(SiMe₃)] [R = SiMe₃ (1) and R = Fc (2)] and ruthenoles Ru₂(CO)₆[μ-η²,η⁴-(Me₃Si)CC{SC(Fc)C(H)}CC(Fc)] 3 and Ru₂(CO)₆[μ-η²,η⁴-(Me₃Si)CC(SCCFc)C(H)C(Fc)] 4, have been obtained from the reactions of M₃(CO)₁₂ (M = Fe, Ru) and FcCCSCCSiMe₃ through S-C bond activations and C-C coupling reactions. Thermolysis of Ru₂(CO)₆[μ₃-η²,η⁴,η³-(Me₃Si)CC{SC(Fc)C(SCCSiMe₃}Ru(CO)₃}CC(Fc)] alone and in the presence of HCCFc, yielded the compounds Ru₂(CO)₆[μ-η²,η⁴-(Me₃Si)CC{SC(Fc)C(SCCSiMe₃)}CC(Fc)] 5 and Ru₂(CO)₆[μ-η²,η⁴-(Me₃Si)CC{SC(Fc)C(SCCSiMe₃)C(H)C(Fc)}CC(Fc)] 6, respectively. The crystal structures of the compounds 1, 3, 4 and 6 are reported.     

Synthesis, characterization and solid state structures of thiosemicarbazone palladacycles: Influence of hydrogen bonding in the molecular arrangement

Treatment of the thiosemicarbazones 4-FC₆H₄C(Me)NN(H)C(S)NHR, (R = Me, a; Ph, b) and 2-ClC₆H₄C(Me)NN(H)C(S)NHR (R = Ph, c) with lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid gave the tetranuclear cyclometallated complex [Pd{4-FC₆H₃C(Me)NNC(S)NHR}]₄ (1a, 1b) and [Pd{2-ClC₆H₃C(Me)NNC(S)NHPh}]₄ (1c). Reaction of these tetramers with the diphosphines dppe, t-dppe, dppp or dppb in a 1:2 molar ratio gave the dinuclear cyclometallated complexes [(Pd{4-FC₆H₃C(Me)NNC(S)NHR})₂(μ-Ph₂P(CH₂)_nPPh₂)], (n = 2, 2a, 2b; 3, 4a, 4b; 4, 5a, 5b), [(Pd{4-FC₆H₃C(Me)NNC(S)NHPh})₂(μ-Ph₂PCHCHPPh₂)], (3a, 3b) and [(Pd{2-ClC₆H₃C(Me)NNC(S)NHR})₂(μ-Ph₂P(CH₂)_nPPh₂)], (n = 2, 2c, 2d; 3, 4c, 4d; 4, 5c, 5d), [(Pd{2-ClC₆H₃C(Me)NNC(S)NHPh})₂(μ-PPh₂CHCHPPh₂)], (3c, 3d). The X-ray crystal structure of the ligand b and the complexes 3c, 4a and 4d were determined. The structures of complexes 4a and 4d show that the different disposition of the chain cyclometallated of the thiosemicarbazones (in the same orientation or in the opposite one) is due to the different H bonds produced.     

Thermodynamic Study of the Aqueous Rubidium and Manganese Bromide System

Crystallization of 2RbBr · MnBr₂ · 2H₂O, the only double salt obtained under standard conditions from saturated aqueous rubidium–manganese bromide solutions, was theoretically predicted using the hard and soft Lewis acids and bases concept and Pauling's rules. The RbBr—MnBr₂—H₂O system was thermodynamically simulated by the Pitzer model assuming a solubility diagram of three branches only: RbBr, 2RbBr · MnBr₂ · 2H₂O and MnBr₂ · 4H₂O. The theoretical result was experimentally proved at 25°C by the physicochemical analysis method and formation of the new double salt 2RbBr · MnBr₂ · 2H₂O was established. It was found to crystallize in a triclinic crystal system, space group –P1, a = 5.890(1) Å, b = 6.885(1) Å, c = 7.367(2) Å, = 66.01(1)°, = 87.78(2)°, = 84.93(2)°, V = 271.8(1) ų, Z = 1, D _x = 3.552 g-cm^–3. The binary and ternary ion interaction parameters were calculated and the solubility isotherm was plotted. The standard molar Gibbs energy of the synthesis reaction, _rG _m ^o , of the double salt 2RbBr · MnBr₂ · 2H₂O from the corresponding simple salts RbBr and MnBr₂ · 4H₂O, as well as the standard molar Gibbs energy of formation, _fG _m ^o , and standard molar enthalpy of formation _fH _m ^o of the simple and double salts were calculated.     

A new rectangular Re4 cluster compound of the metallocyclodiyne Type

The compound (n-Bu₄N)₂[Re₄Cl₈(-Cl)₂(-O)₂ · 2THF] has been prepared from (n-Bu₄N)₂ Re₂Cl₈ by refluxing it in wet trifluoroacetic acid. It forms brown, block-shaped crystals in space group P , withZ = 2 in a cell of dimensions:a = 11.748(1) Å,b = 16.847(3) Å,c = 16.953(3) Å, = 97.53(1)° = 106.49(1)° = 101.25(1)°V = 3093(1) ų. There are two independent but practically identical tetranuclear anions, each on a crystallographic inversion center. The short, unbridged Re-Re edges, to which triple bonds are assigned have lengths of 2.280(1) Å and 2.276(1) Å and the longer edges, each with a -Cl and a -O atom have lengths of 2.611(1) Å and 2.615(1) Å, for molecules 1 and 2 respectively. This anion completes a series going from [Re₄Cl₈(-O)₂(-OMe)₂]^2– through [Re₄Cl₈(-O)₂(-OMe)(-Cl)]^2– to the present [Re₄Cl₈(-O)₂(-Cl)₂]^2–. These metallocyclobutadiynes can be viewed as products of the 2,2-cycloaddition of two Re-Re quadruple bonds, but the mechanistic details of how they arise remain obscure.     

Reactivity differences between molecular and surface silanols in the preparation of homogeneous and heterogeneous olefin metathesis catalysts

The reaction of Mo(N)(CH₂tBu)₃ (1) and SiO_2-(700) generates (SiO)Mo(NH)(CHtBu)(CH₂tBu) (2) when performed in C₆H₆ (material [1/SiO_2-(700)]_C6H6). The grafting occurs presumably by protonation of the nitrido ligand to form an intermediate (SiO)Mo(NH)(CH₂tBu)₃ (3), a pentacoordinated complex, which decomposes into 2 and 2,2-dimethylpropane. While [1/SiO_2-(700)]_C6H6 is highly active in olefin metathesis, [1/SiO_2-(700)]_CH2Cl2 and [1/SiO_2-(700)]_THF are poorly active or inactive catalysts respectively. In contrast, when Mo(N)(CH₂tBu)₃ reacts with a molecular silanol derivative, a soluble model of the surface of SiO_2-(700), it yields a very stable complex, (c-C₅H₉)₇Si₇O₁₂SiO-Mo(NH)(CH₂tBu)₃ (3m), which does not spontaneously generate 2,2-dimethylpropane and an alkylidene complex in contrast to the surface complex. Moreover, 3m does not catalyse olefin metathesis at room temperature as it does not already contain the initiating carbene ligand, and it is necessary to heat up the reaction mixture to 110 °C to obtain low catalytic activity. Nevertheless, the complex 3m generates well-defined metallocarbenes when heated in the presence of PMe₃: (c-C₅H₉)₇Si₇O₁₂SiO-Mo(N)(CHtBu)(P(CH₃)₃)₂ (4m) as a 10:1 mixture of its syn and anti rotamers with the loss of 2 equiv. of 2,2-dimethylpropane.     

New method for the synthesis of σ-β-ketovinyl derivatives of cyclopentadienyliron dicarbonyl

Conclusions A new method was developed for the synthesis of -RCOCH=CHFe(CO)₂C₅H₅- by the reaction of-iodovinyl ketones with [Fe(CO)₂C₅H₅-]₂. In this case it was demonstrated for the first time that the reaction of organic haloderivatives with [Fe(CO)₂C₅H₅-]₂ can be used for the synthesis of -RFe(CO)₂C₅H₅-.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1646–1647, July, 1972.     

Influence of the size of the formed cycle on the reactivity of free radicals in cyclization reactions

Numerous experimental data for the cyclization of free radicals C·H₂(CH₂)_nCH=CH₂ cyclo-[(CH₂)_n+1CH(C·H₂)], and C·H₂(CH₂)_nCH=CHR cyclo-[(CH₂)_n+1C·HCHR] were analyzed in the framework of the parabolic model. The activation energy of thermoneutral (H _e = 0) cyclization E _e0 decreases linearly with an increase in the energy of cycle strain E _rsc: E _e0(n) (kJ mol–1) = 85.5 – 0.44E _rsc(n) (n is the number of atoms in the cycle). The activation entropy of cyclization S ^# also depends on the cycle size: the larger the cycle, the lower S ^#. A linear dependence of S ^# on the difference between the entropies of formation S° of cyclic hydrocarbon and the corresponding paraffin was found: S ^# = 1.00[S°(cycle) – S°(C_nH_2n+2)]. The E _e0 values coincide for cyclization reactions with the formation of the six-membered cycle and the bimolecular addition of alkyl radicals to olefins.     

An approach to the correlation between vanadium-51 shielding and the local symmetry of carbonyl-substituted phosphine vanadium complexes

Summary The⁵¹V n. m. r. spectra of the compounds [Et₄N][V(CO)_6–nL_n] (1) and ⁵-C₅H₅V(CO)_4–nL_n (2) [n = 1,2 (cis andtrans for2); L = PF₃, P(OMe)₃, PMe₃, PPh₂Me], [Et₄N][V(CO)_mL][m = 3–5; L = PhP(CH₂CH₂PPh₂)₂] andcis/trans-[⁵-C₅H₅V(CO)₂L] are discussed on the basis of variations of the paramagnetic contribution _para to the overall shielding of the⁵¹V nucleus. For anionic complexes, _para increases (shielding decreases) as CO is successively replaced for PR₃ (R F), while the neutral complexes exhibit a minimum shielding in disubstituted,trans-configuration compounds. PF₃ complexes show a contrary trend throughout. These trends are explained by (i) decreased energy separation between highest occupied and lowest unoccupied molecular orbitals as the degeneracy is raised plus increased number of relevant transitions in molecules of lower point symmetry, and (ii) destabilization of -type m.o (1 and2) and of -type m.o. (1 only) as V-PR₃ interactions become increasingly important relative to V-CO interactions. _para also increases in the series PF₃ < CO < P(OMe)₃ < PMe₃ < PPh₂Me, following the inverted order of the -acceptor strength. M.o. results obtained from LCAO-SCCC calculations are presented for ⁵-C₅H₅V(CO)₄ and [⁵-C₅H₅V(CO)₃CN]^–: the local diamagnetic contribution to the shielding for these complexes amounts to 1712 ppm and is considered almost constant for all vanadium compounds. The preparations of [Et₄N][V(CO)₅PF₃], andcis-[Et₄N]V(CO)₄L₂] (L = PF₃, PPh₂Me), [Et₄N][V(PF₃]₆, ⁵-C₅H₅V(CO)₃PF₃,cis/trans-[⁵-C₅H₅V(CO)₂(PF₃)₂],cis-[⁵-C₅H₅V(CO)₂(PPh₂Me)₂] and [Et₄N][⁵-C₅H₅V(CO)₃CN] are reported.     

Crystal Structures of Two New Holmium Polysulfides in the Series of Rare-Earth Polychalcogenides

The crystal structures of two polysulfide phases HoS_1.885(5) (I) and HoS_1.863(8) (II) were determined; the integer stoichiometric ratio was found to be Ho₈S₁₅. The data were collected on an Enraf-Nonius CAD-4 automatic diffractometer using the standard procedure (MoK, graphite monochromator, an absorption correction applied based on -scan data). Crystal I: space group P4/nmm, a = 3.820(1), c = 7.840(3) , V = 114.40(6) ³, Z = 2 for the composition HoS_1.885(5), d _calc = 6.542 g/cm³, R = 0.0520 for 184 unique reflections with I_hkl > 2 _I; crystal II: space group P2₁/m, a = 10.961(2), b = 11.465(2), c = 10.984(2) , = 91.27(3)°, V = 1380.0(4) ³, Z = 24 for the composition HoS_1.863(8), d _calc = 6.486 g/cm³, R = 0.0596 for 5354 unique reflections with I_hkl > 2 _I. In both compounds, the Ho atoms are surrounded by 9 (8+1 for three atoms in II) S atoms forming monocapped square antiprisms. The Ho–S distances vary from 2.717 to 3.067 irrespective of the type of ion [S^2– or (S₂)^2–]; the maximal distance to the atoms completing the coordination is 3.684 . The compounds have PbFCl type structures composed of ...(S₂)^2–...Ho³⁺...S^2–...S^2–...Ho³⁺...(S₂)^2–... layer packets differently oriented in space relative to the unit cell axes. The S^2–...S^2– and S^2–...(S₂)^2– interlayer distances are mostly shorter than the sum of the ionic radii and vary within the limits of 3.331-3.558 and 3.029-3.784 for the first and second types, respectively. For I, the calculated site occupancies and densities are given depending on the composition Ho-S_2-x (x = 0.25-0); for II, the most probable formulas of rational compositions in the same range of x are presented.     

Chemical assembly of a new heterometallic trimethylacetate cluster with the Co6Ni2 core

Co-thermolysis of the tetranuclear trimethylacetate clusters M₄(₃-OH)₂(OOCCMe₃)₆(HOEt)₆ (M = Co or Ni; the reagent ratio was 1 : 1) in decalin (2 h, 170 °C) afforded the octanuclear heterometallic cluster Co₆Ni₂(₄-O)₂(₂-OOCCMe₃)₆(₃-OOCCMe₃)₆, which exhibits ferromagnetic properties at 10—8 K.     

Solubility of dichlorotetraalkylpyridinecobalt III hexachlororhenate(IV) in water + methanol mixtures: Free energies of transfer of the complex cation from water into the mixtures

The solubility of salts [Co(3Rpy)₄Cl₂]₂]ReCl₆] has been determined in water + methanol mixtures. By comparing these with the solubilities of the salt Cs₂ReCl₆ and using calculated activity coefficients for the ions in the water+methanol mixtures, values for {G _t ^o (Co(3Rpy)₄Cl ₂ ⁺ )–G _t ^o (Cs⁺)} can be determined where G _t ^o is the standard Gibbs free energy of transfer from water to an aqueous mixture. G _t ^o (Cs⁺) from the solvent sorting scale and from the TPTB scale are then used to calculate G _t ^o (Co(3Rpy)₄Cl ₂ ⁺ ). These two sets of values for G _t ^o (Co(3Rpy)₄Cl ₂ ⁺ ) on the differing scales are then inserted into a free energy cycle applied to the bond extension Co(3Rpy)₄Cl ₂ ⁺ (initial state)Co(3Rpy)₄Cl²⁺+Cl^– (transition state) for the solvolysis in water and in water + methanol mixtures to produce values for G _t ^o (Co(3Rpy)₄Cl²⁺) using both scales. Data for the solubilites of [Copy₄Cl₂]₂[ReCl₆] and [Co(4Rpy)₄Cl₂]₂[ReCl₆] have been re-calculated to compare free energies of transfer for these complex cations with those specified above.     

Optically active triosmium clusters containing the cysteine ligand

The reactions of cysteine ethyl ester with a series of triosmium clusters have been studied. Enantiomeric (-H)Os₃{-SCH₂CH(CO₂Et)NH₂}(CO)₁₀ and diastereomeric (-H)Os₃{-²-SCH₂CH(CO₂Et)NH₂}(CO)₉ forms of the optically active cluster complexes have been obtained. Diastereomeric clusters have been separated by TLC on Silufol plates. The treatment of the enantiomeric complex (-H)Os₃{-SCH₂CH(CO₂Et)NH₂}(CO)₁₀ with the trimethylamine oxide yields the diastereomeric pair (-H)Os₃{-²-SCH₂CH(CO₂Et)NH₂}(CO)₉. The structures of the complexes obtained have been established on the basis of IR,¹H NMR and mass spectrometry as well as X-ray analysis data.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1981–1984, November, 1993.     

Formation of a four-electron donor carbonyl group in the decarbonylation of the unsaturated H2C2Fe2(CO)6 tetrahedrane as an alternative to an iron-iron triple bond

The unsaturated Fe₂C₂ tetrahedrane derivatives R₂C₂Fe₂(CO)₆ (R = Ph, ^tBu) are among the many products obtained from reactions of the alkynes RCCR with iron carbonyls. In this connection theoretical studies have been performed on the simplest such compounds H₂C₂Fe₂(CO)_n (n = 6, 5) for comparison with the experimentally known structure of the t-butyl derivative t-Bu₂C₂Fe₂(CO)₆ and in order to predict the decarbonylation pathways for such (alkyne)Fe₂(CO)₆ derivatives. These theoretical studies predict an Fe₂C₂ tetrahedrane structure for H₂C₂Fe₂(CO)₆ with a formal FeFe double bond very similar to the experimental structure for t-Bu₂C₂Fe₂(CO)₆. Decarbonylation of H₂C₂Fe₂(CO)₆ is predicted to give an H₂C₂Fe₂(CO)₅ isomer retaining the Fe₂C₂ tetrahedrane structure, with an FeFe double bond but with the unprecedented feature of a four-electron donor bridging carbonyl group in an M₂C₂ tetrahedrane structure. The formation of formal FeFe triple bonds appears to be avoided in even the higher energy H₂C₂Fe₂(CO)₅ structures. These include three triplet Fe₂C₂ tetrahedrane structures with formal FeFe double bonds as well as a coordinately unsaturated singlet structure, still with an FeFe double bond.     

Esr study of the reaction of iron carbonyls with sodium alkylthiolates

Conclusions The reaction of iron carbonyls with sodium alkylthiolates proceeds by redox-disproportionation through one-electron transfer to form the Fe₂(CO)₈ , Fe₃(CO)₁₁ Fe₄(CO)₁₃ , and Fe₃(CO)₁₂ radical-anions. Fe₂(CO)₆(SR)₂ and Fe₃(CO)₉(SR)₂ radical-anions are paramagnetic analogs of the reaction products, Fe₂(CO)₆(SR)₂ and Fe₃(CO)₉(SR)₂, and were detected by ESR spectroscopy.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1652–1654, July, 1987.     

A DFT study on the mechanism of the gas phase reaction of ground-state Y (4d5s,D) with 2-butyne

The reaction of ground-state Y with 2-butyne has been investigated in detail using B3LYP method. Four pathways for elimination of H₂ were identified. Two isomers, Y(HCCC)CH₃ and Y(H₂CCCCH₂) were assigned to the observed product, YC₄H₄. The calculated PESs suggest that the concerted H₂-elimination leading to Y(H₂CCCCH₂) + H₂ product is the most favorable pathway. For the elimination of CH₃, combining the results of this work with our previous study on Y + propyne reaction, a general mechanism for the reactions of Y with 2-alkynes bearing RCCCH₃ structure was established: Y + RCCCH₃ → π-complex → TS(H-migration) → HY(CH₂CC)R → TS (CC insertion) → (CH₂)HYCCR → TS(H-migration) → H₃CYCCR → CH₃ + YC₂R. Such mechanism was found to be always energetically more favorable than the direct sp–sp³ CC bond insertion mechanism. Further, such mechanism can also be applied to the elimination of CH₄ and it can be described as: Y + CH₃CCCH₃ → π-complex → TS (H-migration) → HY(H₂CCC)CH₃ → TS(CC insertion) → (H₂CCC)HYCH₃ → TS(H-migration) → CH₄ + YC₃H₂.