Structures and thermochemistry of ions formed by methane chemical ionization of Fe(CO)5. Site of protonation and determination of Fe?H and Fe?CO bond dissociation energies of HFe(CO)n+ ions

High-energy collisional activation mass spectrometry of HFe(CO)₅⁺ ions shows that Fe(CO)₅ is protonated on the iron atom rather than on one of the ligands. This finding is supported by ab initio quantum chemical calculations. The value of the proton affinity of Fe(CO)₅ was measured by high-pressure mass spectrometry to be 857 kJ mol^?1. The Fe? CO bond dissociation energies for HFe(CO)_n⁺ (n = 1–5) were measured by energy-variable low-energy collisional activation mass spectrometry. The Fe? H bond dissociation energies in HFe(CO)_n⁺ ions were also determined. A synergistic effect on the strengths of the Fe? H and Fe? CO bonds in HFe(CO)⁺ is noticed. It is demonstrated that the electronically unsaturated species HFe(CO)_n⁺ (n = 3, 4) formed in exothermic proton-transfer reactions with Fe(CO)₅ form adducts with CH₄. Adducts between C₂H₅⁺ or C₃H₅⁺ and Fe(CO)_n are observed. These adducts are probably formed in direct reactions between the respective carbocations and Fe(CO)₅.     

Mössbauer Study of Some Gamma- and Neutron-Irradiated Iron Carbonyl Complexes

Mössbauer effect experiments have been carried out on ⁶⁰Co and reactor irradiated CFe(CO)₃SCH₁]₂, [(C₄H₉)₂SnFe(CO)₄]₃, (C₆H₅)₁PFe(CO)₄, (CH₂)₄[Fe(CO)₂C₃H₅]₂, and (CH₂)₄.(CO)₂[Fe(CO)₂C₅H₅]₂. It was found that the Fe—CO bond is rather radiation resistant than are expected due to the π bonding character. The σ bonds such as C—H are labile to radiation. The presence of acyl carbonyl group increase the radiation resistant property of the molecule. The increase in the isomer shift values of the complexes with cyclopentadienyl groups were interpreted as a result of dehydrogenation.     

Anomalous behaviour of an allyl alcohol in reaction with iron pentacarbonyl

[(6,7,8,9-η)-Bicyclo[3.2.2]nona-2,6,8-trien-4-ol]tricabonyliron (6) rearranges in the presence of Fe(CO)₅ to [(2,3,6,7-η)-bicyclo[3.2.2]nona-2,6,8-trien-4-one] tricarbonyliron (7); rather than [(6,7,8,9-η)-bicyclo-[3.2.2]nona-6,8-dien-2-one] tricarbonyliron (9), the product expected on the basis of known organoiron chemistry and previously proposed mechanisms. The starting material 6 is stable in the absence of Fe(CO)₅, which leads to the conclusion that some iron-containing species derived from fe(CO)₅ is responsible for bringing about rearrangement. Since the usual mechanism for iron carbonyl-induced rearrangement in olefins cannot be operating here, a mechanism involving an ion pair with [HFe(CO)₄]^- is suggested.     

A radical mechanism for the photochemical iron pentacarbonyl catalyzed hydrogenation of octenes

A high pressure IR and UV spectroscopic study of the catalysis of hydrogenation of 1-octene by Fe(CO)₅ under UV irradiation reveals that Fe(CO)₅ and (olefin)Fe(CO)₄ are the light absorbing species. The primary photolysis product Fe(CO)₄ reacts with H₂Fe(CO)₄ to give HFe(CO)₄ radicals, which are suggested to be the active hydrogenation promoters.     

Übergangsmetall-komplexe mit schwefelliganden: III. Eisen(II)-komplexe mit dem neuen fünfzähnigen thiol-thioether-liganden dpttd-H2 = 2,3,11,12-dibenzo-1,4,7,10,13-pentathia tridecan,synthese und reaktionen von komplexen des typs [Fe(dpttd)L], L = CO,PR3, DMSO,DMF, N2H4

Alkylation of [Fe(S₂C₆H₄)₂(CO)₂]^2? with S(C₂H₄Br)₂ yields loosing one CO ligand the monocarbonyl complex [Fe(dpttd)CO], where dpttd represents the dianion of the novel pentadentate thioether-thiol ligand dpttd-H₂ = 2,3,11,12-dibenzo-1,4,7,10,13-pentathiatridecan. The extremely stable [Fe(dpttd)CO] forms several coordination isomers with different ν(CO) frequencies. Dependent on the reaction conditions, the thermal or photochemical reaction of [Fe(dpttd)CO] with N₂H₅OH yields [Fe(dpttd)(N₂H₄)_2–3] or [Fe(dpttd)(N₂H₄)]·THF; the latter can also be obtained from [Fe(dpttd){P(OPh)₃}] and N₂H₄ in THF at 5–10°C. The CO ligand of [Fe(dpttd)CO] can be substituted thermally by PMe₃, PEt₃, PMePh₂ or P(OPh)₃ yielding the corresponding phosphine and phosphite complexes, but CO substitution by PPh₃ does not take place. Dissolution of [Fe(dpttd)(N₂H₄)_2–3] in dimethyl sulfoxide (DMSO) leads to [Fe(dpptd)(DMSO)], which yields [Fe(dpttd)(DMF)] at 80°C in dimethyl formamide (DMF). [Fe(dpttd)CO] is stable to air in the solid state as well as in solution, however, it decomposes on oxidation by H₂O₂, I₂, Br₂ or N-bromosuccinimide loosing CO and with destruction of the sulfur ligand. All complexes are not very soluble or hardly soluble in all common solvents; this is also found for methyl-substituted [Fe(dpttd)CO], which is obtained from [Fe(S₂C₆Me₄)₂(CO)₂]^2? and S(C₂H₄Br)₂. Oxidation or thermal decomposition of the N₂H₄ complexes yields [Fe(dpttd)]_x, from which [Fe(dpttd)CO] regenerates rapidly on treatment with CO.     

邻异丙硫基苯甲酰基和苯硫甲基铁衍生物的合成与反应

利用异丙基苯硫醚与丁基锂反应后,再依次与羰基铁和碘反应制得了碘桥双核邻异丙硫基苯甲酰基铁配合物[（o-ⁱPrS） C₆H₄COFe（CO）₂I]₂,而苯甲硫醚类似的反应却仅得到单核苯硫甲基铁配合物C₆H₅SCH₂Fe（CO）₃I。当与亲核试剂作用时,这2个化合物表现出显著不同的反应活性。如双核配合物[（o-ⁱPrS） C₆H₄COFe（CO）₂I]₂与2-吡啶硫醇钠（PySNa）反应得到单核配合物（o-ⁱPrS） C₆H₄COFe（CO）₂（SPy）,但单核配合物C₆H₅SCH₂Fe（CO）₃I与PySNa反应导致其分解。另一方面,单核配合物C₆H₅SCH₂Fe（CO）₃I与三苯基膦（PPh₃）反应得到羰基取代配合物C₆H₅SCH₂Fe（CO）₂（PPh₃） I,但是双核配合物[（o-ⁱPrS） C₆H₄COFe（CO）₂I]₂类似的反应却导致其分解,没有获得可表征的化合物。所有新合成的化合物都通过了核磁与红外光谱的表征,它们的结构也获得了X射线单晶衍射的确证。     

On the possibility of existence of η4-π-complexes of corannulene (C20H10) and Ñ60 fullerene derivatives

The problem of existence of ⁴--complexes of transition metal atoms with Ñ₆₀ fullerene and its simplest bowl-shaped hydrocarbon precursor, corannulene (Ñ₂₀H₁₀), is discussed in the framework of the HF/3-21G and DFT/TZ2P methods. The molecular structures of corannulene and Ñ₆₀ fullerene derivatives, namely, C₂₀H₁₄, C₂₀H₁₆, C₆₀H₄, and C₆₀H₆ were simulated. These molecules can form stable ⁴--complexes C₂₀H₁₄Fe(CO)₃, C₂₀H₁₆Fe(CO)₃, C₆₀H₄Fe(CO)₃, and C₆₀H₆Fe(CO)₃ in which the Fe atom interacts with C atoms of a fulvene-like or butadiene-like conjugated fragment of the hydrocarbon ligands. The energies of the ⁴--bonds in the complexes under study were compared with the corresponding bond energies in the classical complexes C₄H₆Fe(CO)₃ and C₅H₆Fe(CO)₃. The geometric parameters of C₄H₆Fe(CO)₃ and C₅H₆Fe(CO)₃ obtained from DFT calculations are close to the experimental values. Stabilities of the ⁴--complexes studied and their ⁵--analogs were compared.     

邻异丙硫基苯甲酰基和苯硫甲基铁衍生物的合成与反应

利用异丙基苯硫醚与丁基锂反应后,再依次与羰基铁和碘反应制得了碘桥双核邻异丙硫基苯甲酰基铁配合物[（o-ⁱPrS）C₆H₄COFe（CO）₂I]2,而苯甲硫醚类似的反应却仅得到单核苯硫甲基铁配合物C₆H₅SCH₂Fe（CO）₃I。当与亲核试剂作用时,这2个化合物表现出显著不同的反应活性。如双核配合物[（o-ⁱPrS）C₆H₄COFe（CO）₂I]2与2-吡啶硫醇钠（PySNa）反应得到单核配合物（o-ⁱPrS）C₆H₄COFe（CO）₂（SPy）,但单核配合物C₆H₅SCH₂Fe（CO）₃I与PySNa反应导致其分解。另一方面,单核配合物C₆H₅SCH₂Fe（CO）₃I与三苯基膦（PPh₃）反应得到羰基取代配合物C₆H₅SCH₂Fe（CO）₂（PPh₃）I,但是双核配合物[（o-ⁱPrS）C₆H₄COFe（CO）₂I]2类似的反应却导致其分解,没有获得可表征的化合物。所有新合成的化合物都通过了核磁与红外光谱的表征,它们的结构也获得了X射线单晶衍射的确证。     

Structure and Reactivity of Iron(0)-Phenyltellurolate [PPN][PhTeFe(CO)4]

Anionic iron(0) tetracarbonyl with terminal phenyltellurolate ligand PhTe^?, [PhTeFe(CO)₄]^?, has been synthesized and characterized. The title compound was obtained by addition of (PhTe)₂ to [PPN][HFe(CO)₄] THF solution dropwise. [PPN][PhTeFe(CO)₄] crystallizes in the monoclinic space group C c, with a = 16.119(4) Å, b = 13.141(3) Å, c = 19.880(8) Å, β = 93.04(3)°, V = 4205(2) ų, and Z = 4. The [PhTeFe(CO)₄]^? anion is a trigonal-bipyramidal complex in which the phenyltellurolate ligand occupies an axial position with Fe-Te bond length 2.630(5) Å and the Fe-Te-C(Ph) angle is 103.4(5)°. The neutral iron(0)-telluroether compound, (PhTeMe)Fe(CO)₄, was prepared by alkylation of the [PhTeFe(CO)₄]^?. Protonation of [PhTeFe(CO)₄]^?and reaction of H₂Fe(CO)₄ and PhTe)₂ ultimately lead to formation of the known dimer Fe₂(μ-TePh)₂(CO)₆ and H₂.     

Photochemical reactions of cationic isocyanide/carbonyl complexes of iron with selected nucleophiles

Photolysis of (η⁵-C₅H₅Fe(CO)(CNMe)₂]PF₆ in the presence of excess nucleophiles resulted in efficient substitution of the carbonyl ligand, generating the new isocyanide complexes (η⁵-C₅H₅Fe(CNMe)₂)(L)]PF₆ (L = PPh₃, AsPh₃, SbPh₃, pyridine, acetonitrile, and ethylene). Similar reactions of (η⁵-C₅H₅Fe(CO)_2)(CNMe)PF₆ led to sequential replacement of both carbony groups with the exception of L  ethylene. No evidence of photochemical isocyanide substitution was found. The same carbonyl complexes failed to reach with L thermally. In the absence of light, ethylene, pyridine, and acetonitrile complexes were found to disporportionate in the manner [η⁵-C₅H₅Fe(CNMe)(L)₂]PF₆→ [η⁵C₅H₅Fe(CNMe)₂(L)]PF₆ → [η⁵-C₅H₅Fe(CNMe)₃]PF₆ with the first rearrangement occurring much faster than the second. The new isocyanide complexes are characterized by their infrared and NMR (¹H, ¹³C) spectra.     

Stabilization of highly reactive cyclic polyolefins by coordination to iron carbonyls: cis-cyclononatetraene-iron tricarbonyl

Reaction of cis-bicyclo[6.1.0]nona-2,4,6-triene (C₉H₁₀) (I) with Fe₂(CO)₉, at room temperature, yields a number of complexes (IV)–(IX). One of the e, (IX), is the Fe₂(CO)₆ derivative of the starting polyolefin (I), whereas the others are Fe(CO)₃ or Fe(CO)₄ complexes of isomeric C₉H₁₀ polyolefins.(IV) is (h⁴-l,2,3,4-cis-8,9-dihydroindene)iron tricarbonyl, (V) is tentatively formulated as (h²-or h²-5,6-cis-bicyclo[5.2.0]nona-2,5,8-triene)iron tetracarbonyl, (VI) has been characterized only as C₉H₁₀Fe(CO)₃, and (VII) and (VIII) are the asymmetric and symmetric isomers (h⁴-cis-cyclononatetraene)iron tricarbonyl. Characterization of the complexes has been obtained through PMR, IR, and mass spectra.Peculiar features of this reaction are the promotion of the polyolefin (I) rearrangement by iron carbonyls and the stabilization of highly reactive intermediates through coordination to the metal carbonyl groups. fa]Work presented in part at the 3rd International Symposium on Reactivity and Bonding in Transition Organometallic Compounds, Venice, September 9–10, 1970.     

Cyclobutadieneiron nitrosyl complexes

The air stable yellow-orange complexes of cyclobutadieneiron dicarbonyl nitrosyl hexafluorophosphate, [R₄C₄Fe(CO)₂NO]⁺PF^-₆; R = H, CH₃, Ph, were prepared by the reaction of R₄C₄Fe(CO)₃ and nitrosonium hexafluorophosphate. These complexes undergo facile monocarbonyl substitution reactions with various Lewis bases (L) to afford products of the type [R₄C₄Fe(CO)(NO)L]⁺PF^-₆, R = H, L = Ph₃P, Ph₃As, Ph₃Sb or R = Ph; L = Ph₃P, Ph₃As; a dicarbonyl substitution product of the type [R₄C₄Fe(NO)L₂]⁺PF^-₆, R = Ph; L = (PhO)₃P, was also isolated and characterized.     

The reaction of trichlorosilyltetracarbonyliron hydride (HFe(CO)4SiCl3) with conjugated dienes

Isoprene, 1,3-butadiene and 2,3-dimethyl-1,3-butadiene react with HFe(CO)₄SiCl₃ by addition of the Fe---H function to the diene. Isoprene appears to add predominantly 1,4 and 2,3-dimethyl-1,3-butadiene appears to add 1,2, while 1,3-butadiene may add both ways. In the case of isoprene and 1,3-butadiene loss of CO from the addition compound gives a stable π-allyl- Fe(Co)₃SiCl₃ product. Either cis- or trans-1,3-pentadiene is reduced to pentene by HFe(CO)₄SiCl₃.     

Heterobimetallische phosphanido-verbrückte Zweikern-Komplexe - Synthese von cis-rac-[(η-C5H4R)2Zr{μ-PH(2,4,6−iPr3C6H2)}2M(CO)4] (RMe,MCr,Mo; RH,MMo)

Heterobimetallic Phosphanido-bridged Dinuclear Complexes - Syntheses of cis-rac-[(η-C₅H₄R)₂Zr{μ-PH(2,4,6-ⁱPr₃C₆H₂)}₂M(CO)₄] (R?Me, M?Cr, Mo; R?H, M?Mo) The zirconocene bisphosphanido complexes [(η-C₅H₄R)₂Zr{PH(2,4,6-ⁱPr₃C₆H₂)}₂] (R?Me, H) react with [(NBD)M(CO)₄] (NBD?norbornadiene, M?Cr, Mo) to give only one diastereomer of the phosphanido-bridged heterobimetallic dinuclear complexes cis-rac-[(η-C₅H₄R)₂Zr{μ-PH(2,4,6-ⁱPr₃C₆H₂)}₂M(CO)₄] [R?Me, M?Cr ( 1 ), Mo ( 2 ); R?H, M?Mo ( 3 )]. However, no reaction was observed between [(η-C₅H₅)₂Zr{PH(2,4,6-^tBu₃ C₆H₂)}₂] and [Pt(PPh₃)₄]. 1—3 were characterised spectroscopically. For 1—3 , the presence of the racemic isomer was shown by NMR spectroscopy. No reaction was observed at room temperature for 3 and CS₂, (NO)BF₄, Me₃NO or PH(2,4,6-Me₃C₆H₂)₂. With Et₂AlH or PhC?CH decomposition of 3 was observed.     

Übergangsmetall-substituierte phosphane,arsane und stibane: XXXVI. Diastereomere dreikernkomplexe mit verbrückenden dimethylarsino-, dimethylstibino- oder dimethylbismutino-einheiten

Interaction of the chiral organometallic Lewis bases Cp(CO)(Me₃P)Fe—EMe₂ (E = As, Sb, Bi) (1a–1c) with the norbornadiene metal complex (C₇H₈)Mo(CO)₄ yields the first examples of trinuclear complexes [Cp(CO)(Me₃P)Fe—EMe₂]₂Mo(CO)₄ (2a–2c), bearing two chiral metal atoms separated by a E—Mo—E-linkage. 2a–2c are generated as a mixture of two diastereomers (RS/SR, RR/SS), which gives rise to a resonance doubling in their ¹H and ³¹P NMR spectra. This phenomenon is not observed for the achiral, in part sterically more crowded derivatives [Cp(CO)₂Fe—SbMe₂]₂Mo(CO)₄ (4) and [Cp(CO)₂(Me₃P)Mo—EMe₂]₂Mo(CO)₄ (E = As, Sb (6a, 6b)), which excludes the existence of conformers resulting from restricted rotation about the FeE or MoE bond in the case of 2a–2c.     

Über ein carbonyleisenhaltiges schwefelylid

From the reaction of [π-C₅H ₅Fe(CO)₃]⁺PF₆^- with two equivalents of (CH₃)₂S-(O)CH₂ in THF a yellow complex of composition (π-C₅H₅)(CO)₂Fe—C(O)—CH—S(O)(CH₃)₂ is obtained in addition to (CH₃)₃SOPF₆. The chemical and spectroscopic properties of the iron complex are described.     

Ligand Site Preference in Iron Tetracarbonyl Complexes Fe(CO)4L (L = CO,CS, N2, NO+, CN–, NC–, η2‐C2H4, η2‐C2H2, CCH2, CH2, CF2, NH3, NF3, PH3, PF3, η2‐H2)

Equilibrium geometries, bond dissociation energies and relative energies of axial and equatorial iron tetracarbonyl complexes of the general type Fe(CO)₄L (L = CO, CS, N2, NO⁺, CN^–, NC^–, η²‐C₂H₄, η²‐C₂H₂, CCH₂, CH₂, CF₂, NH₃, NF₃, PH₃, PF₃, η²‐H₂) are calculated in order to investigate whether or not the ligand site preference of these ligands correlates with the ratio of their σ‐donor/π‐acceptor capabilities. Using density functional theory and effective‐core potentials with a valence basis set of DZP quality for iron and a 6‐31G(d) all‐electron basis set for the other elements gives theoretically predicted structural parameters that are in very good agreement with previous results and available experimental data. Improved estimates for the (CO)₄Fe–L bond dissociation energies (D₀) are obtained using the CCSD(T)/II//B3LYP/II combination of theoretical methods. The strongest Fe–L bonds are found for complexes involving NO⁺, CN^–, CH₂ and CCH₂ with bond dissociation energies of 105.1, 96.5, 87.4 and 83.8 kcal mol^–1, respectively. These values decrease to 78.6, 64.3 and 64.2 kcal mol^–1, respectively, for NC^–, CF₂ and CS. The Fe(CO)₄L complexes with L = CO, η²‐C₂H₄, η²‐C₂H₂, NH₃, PH₃ and PF₃ have even smaller bond dissociation energies ranging from 45.2 to 37.3 kcal mol^–1. Finally, the smallest bond dissociation energies of 23.5, 22.9 and 18.5 kcal mol^–1, respectively are found for the ligands NF₃, N₂ and η²‐H₂. A detailed examination of the (CO)₄Fe–L bond in terms of a semi‐quantitative Dewar‐Chatt‐Duncanson (DCD) model is presented on the basis of the CDA and NBO approach. The comparison of the relative energies between axial and equatorial isomers of the various Fe(CO)₄L complexes with the σ‐donor/π‐acceptor ratio of their respective ligands L thus does not generally support the classical picture of π‐accepting ligands preferring equatorial coordination sites and σ‐donors tending to coordinate in axial positions. In particular, this is shown by iron tetracarbonyl complexes with L = η²‐C₂H₂, η²‐C₂H₄, η²‐H₂. Although these ligands are predicted by the CDA to be stronger σ‐donors than π‐acceptors, the equatorial isomers of these complexes are more stable than their axial pendants.     

The photoreaction of the (η-C5H5)Fe(CO)2I—diisopropylamine system with pyrrole and indole

η-C₅H₅)Fe(CO)₂ I reacts with pyrrole and indole in the presence of diisopropylamine, in sunlight, to give the corresponding (η-C₅H₅)Fe(CO)₂-η¹-N-heterocyclic complexes in 72–88% yield.     

Di- and poly-nuclear transition metal complexes as catalysts for the metal carbonyl substitution reaction. The role of supported metals and metal oxides as catalyst promoters

Various di- and poly-nuclear transition metal complexes have been investigated as catalysts for the metal carbonyl substitution reaction. The complexes [{(η⁵-C₅H₄R)Fe(CO)₂} ₂] (R = H, Me, CO₂Me, OMe, O(CH₂)₄OH) and [{(η⁵-C₅H₅)-Ru(CO)₂} ₂] are active catalysts for a range of substitution reactions including the probe reaction [Fe(CO)₄(CNBu^t)] + Bu^tNC → [Fe(CO)₃(CNBu^t)₂] + CO. [{(η⁵-C₅Me₅)Fe(CO)₂}₂] is catalytically active only on irradiation with visible light. For [{η⁵-C₅H₅)Fe(CO)₂}₂] and a range ofisocyanides RNC ( R = Bu^t, C₆H₅CH₂, 2,6-Me₂C₆H₃), catalyst modification by substitution with isocyanide is a major factor influencing the degree of the catalytic effects observed, e.g. [{(η⁵-C₅H₅)Fe(CO)(CNBu^t)}₂] is approximately 35 times as active as [(η⁵-C₅H₅)₂FE₂(CO)₃(CNBu^t)] for the [Fe(CO)₄(CNBu^t)] → [Fe(CO)₃(CNBu^t)₂] conversion. Mechanistic studies on this system suggest that the catalytic substitution step probably involves a rapid intermolecular attack of isonitrile, possibly on a labile catalyst-substrate radical intermediate such as {[Fe(CO)₄(CNR)][(η⁵-C₅H₅)Fe(CO)₂]}; or on a reactive radical cation such as [Fe(CO)₄(CNR)]⁺ generated via electron transfer between the substrate and the catalyst. Other transition metal complexes which also catalyze the substitution of CO by isocyanide in [Fe(CO)₄(CNR)] (and [M(CO)₆] (M = Cr, Mo, W), [Mn₂(CO)₁₀], [Re₂(CO)₁₀]) include [Ru₃(CO)₁₂], [H₄Ru₄(CO)₁₂], [M₄(CO)₁₂] (M = Co, Ir) and [Co₂(CO)₈]. These reactions conform to the general mechanistic patterns established for [{(η⁵-C₅H₅)Fe(CO)₂}₂], suggesting a similar mechanism. A range of materials, notably PtO₂, PdO and Pd/C, act as promoters for the homogeneous di- and poly-nuclear transition metal catalysts, and can even be used to induce activity in normally inactive dimer and cluster complexes e.g. [Os₃(CO)₁₂]. This promotion is attributed to at least three possible effects: the removal of catalyst inhibitors, a catalyzed substitution of the homogeneous catalyst partner, and a possible homogeneous-heterogeneous interaction which promotes the formation of catalytic intermediates.     

Iron(II) carbonyl complexes containing xanthate,dithiocarbamate or dithiophosphate ligands

Summary Starting from Fe(CO)₄I₂, octahedral Fe^II carbonyl derivatives of the types Fe(CO)₂(xan)₂, Fe(CO)₃(xan)I and Fe(CO)₃(dtc)I were prepared (xan = xanthate, dtc = dithiocarbamate). Infrared evidence was obtained for the formation of Fe(CO)₂(dtp)₂ complexes (dtp = dithiophosphate). The dixanthate complexes are also formed from Fe^II salts and potassium xanthates by CO absorption in MeOH/H₂O solution.