Complicated Mixture Of Products Research Articles

(Invited) Optimization of Carbonate Electrolytes for Lithium Metal Anodes

A solid electrolyte interphase (SEI) is generated on the anode of lithium ion batteries during the first few charging cycles. While the SEI generated for LiPF6/carbonate based electrolytes is stable on graphite anodes, the stability of the SEI is poor for LiPF6/carbonate based electrolytes with lithium metal anodes. However, modification of the carbonate based electrolytes via incorporation of alternative salts and/or electrolyte additives significantly improves the stability of the SEI and the cycle life of lithium metal anodes. Investigations of the SEI structure have been conducted via a combination of XPS, IR-ATR, SEM, and TEM. Mechanisms for the generation of the complicated mixture of products are presented along with the differences in the SEI structure and function.

Dinucleating ligands based on functionalized oxalamides: Lability of Re(I) coordination with the phosphorus pendant arms

The reactions of ortho-(thio)phosphorylated anilines with oxalyl chloride smoothly afforded new ditopic pincer ligands with an oxalamide core and phosphorus(V) pendant arms. The thiophosphoryl-functionalized oxalamide readily underwent direct cyclometalation under the action of Re(CO)5Br in the presence of a base, furnishing the expected ditopic Re(I) pincer complex. At the same time, its phosphoryl-containing counterpart, owing to the labile coordination of the PO groups, afforded a complicated mixture of products, which finally resulted in two binuclear complexes with either coordinated or uncoordinated phosphoryl arms. The structures of all the isolated complexes were elucidated using NMR and IR spectroscopy as well as X-ray diffraction analysis, which provided some insight into the mechanism of their formation. The results of the preliminary evaluation of cytotoxic properties of some of the Re(I) complexes are presented.

Copper Complexes of Benzoylacetone Bis-Thiosemicarbazones: Metal and Ligand Based Redox Reactivity

Bis-thiosemicarbazones derived from the β-diketone benzoylacetone (H3banR, R=Me, Et, Ph) are potentially tetradentate N2S2 ligands whose coordination chemistry with copper is reported. In the absence of oxygen and in the presence of base they form anionic CuII complexes of the fully deprotonated ligands [CuII(banR)]–. Upon exposure to atmospheric oxygen they undergo a complex series of reactions leading to two types of products; one a ligand oxidised ketone complex [CuII(banRO)] and the other an unprecedented dimeric di-CuIII complex [(CuIII(banR))2] depending on the R substituent. Time-resolved UV-vis spectroscopy, cyclic voltammetry, spectroelectrochemistry, and electron paramagnetic resonance (EPR) spectroscopy have been used to identify intermediates on the way to stable products formed under both anaerobic and aerobic conditions. It is found that both ligand-centred and Cu-centred oxidation reactions are occurring in parallel leading to this unusually complicated mixture of products.

(Invited) Generation and Evolution of Materials in the Anode Solid Electrolyte Interphase (SEI) of Lithium Ion Batteries

A solid electrolyte interphase is generated on the anode of lithium ion batteries during the first few charging cycles. The presence and stability of the solid electrolyte interphase (SEI) is critical to the performance of the battery. Despite thorough investigation of the SEI for over 20 years, the mechanism of formation and function are still relatively poorly understood. We have investigated the structure of the initial SEI on graphite and silicon electrodes along with changes which occur to the SEI upon additional cycling via a combination of ex-situ surface analysis techniques. The investigation of SEI provides significant insight into the structure and properties of the anode SEI. The one electron reducing agent, lithium napthalenide has been used to independently prepare the reduction products which constitute the SEI. The initial reduction product of ethylene carbonate is lithium ethylene dicarbonate (LEDC). However, the thermal decomposition of LEDC and related lithium alkyl carbonates in the presence of LiPF6 generates a intricate mixture of compounds which greatly complicates the structure of the SEI. The reduction products and their subsequent thermal decomposition products have been thoroughly investigated via a combination of NMR, XPS, IR-ATR, TGA, and GC-MS. Mechanisms for the generation of the complicated mixture of products will be discussed. Thermal behavior of the SEI on a silicon electrode for Lithium ion batteries has been investigated by TGA. In order to provide a better understanding of the thermal decomposition of the SEI on silicon, the thermal decomposition behavior of independently synthesized lithium ethylene dicarbonate (LEDC) was investigated as a model SEI. The model SEI (LEDC) has three stages of thermal decomposition. Over the temperature range of 50~300oC, LEDC decomposes to evolve CO2 and C2H4 gasses leaving lithium propanoate (CH3CH2CO2Li) and Li2CO3 as solid residues. The lithium propanoate decomposes over the temperature range of 300~600oC to evolve pentanone leaving Li2CO3 as a residual solid. Finally, the Li2CO3 decomposes over 600oC to evolve CO2 leaving Li2O as a residual solid. A very similar thermal decomposition process is observed for the SEI generated on cycled silicon electrodes. However, two additional thermal decomposition reactions were observed characteristic of LixPOyFz at 300oC and the polyimide binder at 550oC. TGA measurements of Si electrodes after various numbers of cycles suggest that the LEDC on Si electrodes thermally decomposes during cycling to form lithium propanoate and Li2CO3, resulting in increased complexity of the SEI.

Generation and Evolution of Materials in the Anode Solid Electrolyte Interphase (SEI) of Lithium Ion Batteries

A solid electrolyte interphase is generated on the anode of lithium ion batteries during the first few charging cycles. The presence and stability of the solid electrolyte interphase (SEI) is critical to the performance of the battery. Despite thorough investigation of the SEI for over 20 years, the mechanism of formation and function are still relatively poorly understood. We have investigated the structure of the initial SEI on graphite and silicon electrodes along with changes which occur to the SEI upon additional cycling via a combination of ex-situ surface analysis techniques. The investigation of SEI provides significant insight into the structure and properties of the anode SEI. The one electron reducing agent, lithium napthalenide has been used to independently prepare the reduction products which constitute the SEI. The initial reduction product of ethylene carbonate is lithium ethylene dicarbonate (LEDC). However, the thermal decomposition of LEDC and related lithium alkyl carbonates in the presence of LiPF6 generates a intricate mixture of compounds which greatly complicates the structure of the SEI. The reduction products and their subsequent thermal decomposition products have been thoroughly investigated via a combination of NMR, XPS, IR-ATR, TGA, and GC-MS. Mechanisms for the generation of the complicated mixture of products will be discussed. Thermal behavior of the SEI on a silicon electrode for Lithium ion batteries has been investigated by TGA. In order to provide a better understanding of the thermal decomposition of the SEI on silicon, the thermal decomposition behavior of independently synthesized lithium ethylene dicarbonate (LEDC) was investigated as a model SEI. The model SEI (LEDC) has three stages of thermal decomposition. Over the temperature range of 50~300oC, LEDC decomposes to evolve CO2 and C2H4 gasses leaving lithium propanoate (CH3CH2CO2Li) and Li2CO3 as solid residues. The lithium propanoate decomposes over the temperature range of 300~600oC to evolve pentanone leaving Li2CO3 as a residual solid. Finally, the Li2CO3 decomposes over 600oC to evolve CO2 leaving Li2O as a residual solid. A very similar thermal decomposition process is observed for the SEI generated on cycled silicon electrodes. However, two additional thermal decomposition reactions were observed characteristic of LixPOyFz at 300oC and the polyimide binder at 550oC. TGA measurements of Si electrodes after various numbers of cycles suggest that the LEDC on Si electrodes thermally decomposes during cycling to form lithium propanoate and Li2CO3, resulting in increased complexity of the SEI.

Unexpected detours and reactivity encountered during the planned synthesis of hypervalent 10–Pn–3 species (Pn = P or As)

The planned synthesis of hypervalent 10–P–3 and 10–As–3 compounds 1 and 2 from brominated bis(oxazoline) and bis(imine) NCN pincers via a lithiation/electrophilic quenching (with PnCl3; Pn=P or As)/reduction protocol resulted in unexpected findings and reactivity. Generation of bis(oxazoline)-ligated (NCN)PCl2 derivative CP resulted in an intramolecular SN2 reaction, leading to formation of ring-opened 3, which could be phenylated with PhMgBr to give 4. In solution, bis(imine)-based (NCN)PCl2 analogue DP displayed a complicated product mixture by 31P{1H} NMR spectroscopy, likely due to the presence of several ionic species and iminium-enamine tautomers, while the As derivative (DAs) was isolable and crystallized in a distorted square pyramidal geometry. Reduction of both derivatives of D with PMe3 did not afford the targeted 10–Pn–3 (Pn=P or As) species 2, but rather generated rare examples of dynamic bell-clappers. [Display omitted]

New insights into the action of bacterial chondroitinase AC I and hyaluronidase on hyaluronic acid

Hyaluronic acid (HA), a glycosaminoglycan, is a linear polysaccharide with negative charge, composed of a repeating disaccharide unit [→4)-β-d-glucopyranosyluronic acid (1→3)-β-d- N-acetyl-d-glucoaminopyranose (1→]n ([→4) GlcA (1→3) GlcNAc 1→]n). It is widely used in different applications based on its physicochemical properties associated with its molecular weight. Enzymatic digestion by polysaccharides lyases is one of the most important ways to decrease the molecular weight of HA. Thus, it is important to understand the action patterns of lyases acting on HA. In this study, the action patterns of two common lyases, Flavobacterial chondroitinase AC I and Streptomyces hyaluronidase, were investigated by analyzing HA oligosaccharide digestion products. HA oligosaccharides having an odd-number of saccharide residues were observed in the products of both lyases, but their distributions were quite different. Chondroitinase AC acted more efficiently at the β 1–4 glycosidic bond linking GlcNAc and GlcA. Oligosaccharides, having an even number of saccharide residues, and with an unsaturated uronic acid (4-deoxy-α-l-threo-hex-4-enepyranosyluronic acid, △UA) residue at their non-reducing end represent the major product. A minor amount of oligosaccharides having an odd number of saccharide residues resulted from the irregular terminal residues of HA substrate chains. Hyaluronidase showed a more complicated product mixture. Its minimum recognition and digestion domain is HA heptasaccharide and it could cleave both β 1–4 and β 1–3 glycosidic linkages. The HA oligosaccharides, generated with a 2-acetamido-2,3-di-deoxy-β-d-erythro-hex-2-enopyranose (△HexNAc) at the non-reducing end, are believed to be unstable and undergo breakdown immediately after their generation, and the oligosaccharides with △UA residue at the non-reducing end are formed. Thus, oligosaccharides having both an even and odd-number saccharide residues with a △UA residue at their non-reducing ends, represent the major products of hyaluronidase acting on HA.

Low coordinate iron derivatives stabilized by a β-diketiminate mimic. Synthesis and coordination chemistry of enamidophosphinimine scaffolds to generate diiron dinitrogen complexes.

In an effort to mimic N-diaryl-β-diketiminate ligands (Nacnac), we have converted N-arylimine phosphine ligands to enamine-phosphinimines via the Staudinger reaction. By varying the aryl azide, one can access enamine-phosphinimine ligands with the same or different N-aryl substituents on both the enamine and phosphinimine units, which allows this intrinsically unsymmetrical bidentate donor set to present variable steric effects at the metal center. The enamine-phosphinimine was deprotonated and used in metathetical reactions with Fe(ii) bromide precursors to generate low coordinate complexes of the empirical formula [(CY5)NpN(Ar,Ar')]FeBr (where CY5 = cyclopentenyl; Ar,Ar' = 2,6-diisopropylphenyl, 2,6-dimethylphenyl, 2,4,6-trimethylphenyl). Depending on the substituents, these bromide derivatives can be monomeric or dimeric via bromide bridges. Reduction under dinitrogen using potassium graphite generates the dinitrogen complexes ([(CY5)NpN(Ar,Ar')]Fe)2(μ-N2) for Ar,Ar' = 2,6-diisopropylphenyl, and Ar = 2,6-dimethylphenyl, Ar' = 2,4,6-trimethylphenyl. However, for the former, a unsymmetrical side product can be isolated that has a bridging N-2,6-diisopropylphenylimide unit with one enamido-phosphine ligand bound to one iron and the other iron stabilized with an intact enamido-phosphinimine. When the steric bulk is reduced on both nitrogen donors, a complicated product mixture is obtained after reduction from which a small amount of [(CY5)NpN(Ar,Ar')]Fe[(CY5)NP(Ar)] (Ar,Ar' = 2,6-dimethylphenyl) could be isolated. All of these complexes are paramagnetic and have been characterized by elemental analysis, magnetic studies and X-ray crystallography.

Rapid, Reversible, Solid-Gas and Solution-Phase Insertion of CO2 into In-P Bonds.

The P,P-chelated heteroleptic complex bis[bis(diisopropylphosphino)amido]indium chloride [(i-Pr2P)2N]2InCl was prepared in high yield by treating InCl3 with 2 equiv of (i-Pr2P)2NLi in Et2O/tetrahydrofuran solution. Samples of [(i-Pr2P)2N]2InCl in a pentane slurry, a CH2Cl2 solution, or in the solid state were exposed to CO2, resulting in the insertion of CO2 into two of the four M-P bonds to produce [O2CP(i-Pr2)NP(i-Pr2)]2InCl in each case. Compounds were characterized by multinuclear NMR and IR spectroscopy, as well as single-crystal X-ray diffraction. ReactIR solution studies show that the reaction is complete in less than 1 min at room temperature in solution and in less than 2 h in the solid-gas reaction. The CO2 complex is stable up to at least 60 °C under vacuum, but the starting material is regenerated with concomitant loss of carbon dioxide upon heating above 75 °C. The compound [(i-Pr2P)2N]2InCl also reacts with CS2 to give a complicated mixture of products, one of which was identified as the CS2 cleavage product [S═P(i-Pr2)NP(i-Pr2)]2InCl]2(μ-Cl)[μ-(i-Pr2P)2N)].

Isoclast Active Manufacture: In Situ Spectroscopic Investigation of the Unstable Products of Cyanamide and Sodium Hypochlorite Reactions

Isoclast Active is a new insecticide manufactured by Dow AgroSciences LLC. In an effort to lower the cost of manufacture of Isoclast Active, we have studied the reaction which produces N-cyano sulfilimine, which is the precursor to Isoclast Active. The reaction involves the oxidative coupling of cyanamide with the sulfide intermediate using sodium hypochlorite. In this study, we demonstrated that a transient intermediate species is produced by the reaction between bleach and cyanamide. On the basis of in situ Raman, IR, and NMR spectroscopic evidence we propose that the intermediate is the anionic form of N-chlorocyanamide: ClN––C≡N. The degradation of this intermediate species was found to be highly sensitive to its environment and leads to a complicated mixture of products. This work also demonstrates that in situ Raman and IR spectroscopy are powerful and invaluable tools for monitoring reactions/processes involving unstable reaction intermediates for kinetic modeling and process R&D.

Acetylacetonato(phosphane)iridium Complexes: Synthesis and Catalytic Activity in the Cyclization of Alkynoic Acids

AbstractThe iridium complex [Ir(acac)(η2‐coe)2] (1) has been easily prepared by the addition of Tl(acac) to a suspension of [Ir(μ‐Cl)(η2‐coe)2]2 in hexane. Complex 1 has been characterized fully including an X‐ray diffraction study. It is moderately stable and is a useful precursor to a number of different acetylacetonato(phosphane)iridium complexes via addition of monodentate and bidentate phosphanes. Reactions proceeded at room temperature to give high yields of the desired square planar phosphane complexes [Ir(acac)(P)] (2: P = 2 PPh3, 3: P = 2 PMePh2, 4: P = dppm, 5: P = dppe, 6: P = dppp, 7: P = dppb, 8: P = dppf, 9: P = dcpe) except for those involving dppe, which gave a complicated mixture of products. Complex [Ir(acac)(dppe)] (5) was prepared in a microwave reactor at 125 °C. All complexes prepared in this study were efficient in the intramolecular catalyzed cyclization of4‐pentynoic acid to give exclusive formation of the exocyclic γ‐methylene‐γ‐butyrolactone. Complex 1 was found to be the most active and selective catalyst precursor for the intramolecular cyclization of both 4‐pentynoic acid and 5‐hexynoic acid.

Structural basis for regioisomerization in the alkali-metal-mediated zincation (AMMZn) of trifluoromethyl benzene by isolation of kinetic and thermodynamic intermediates.

Performed with a desire to advance knowledge of the structures and mechanisms governing alkali-metal-mediated zincation, this study monitors the reaction between the TMP-dialkylzincate reagent [(TMEDA)Na(TMP)(tBu)Zn(tBu)] 1 and trifluoromethyl benzene C6H5CF32. A complicated mixture of products is observed at room temperature. X-ray crystallography has identified two of these products as ortho- and meta-regioisomers of heterotrianionic [(TMEDA)Na(TMP)(C6H4-CF3)Zn(tBu)], 3-ortho and 3-meta, respectively. Multinuclear NMR data of the bulk crystalline product confirm the presence of these two regioisomers as well as a third isomer, 3-para, in a respective ratio of 20:11:1, and an additional product 4, which also exhibits ortho-zincation of the aryl substrate. Repeating the reaction at 0 °C gave exclusively 4, which was crystallographically characterized as [{(TMEDA)2Na}+{Zn(C6H4-CF3)(tBu)2}−]. Mimicking the original room-temperature reaction, this kinetic product was subsequently reacted with TMP(H) to afford a complicated mixture of products, including significantly the three regioisomers of 3. Surprisingly, 4 adopts a solvent-separated ion pair arrangement in contrast to the contacted ion variants of 3-ortho and 3-meta. Aided by DFT calculations on model systems, discussion focuses on the different basicities, amido or alkyl, and steps, exhibited in these reactions, and how the structures and bonding within these isolated key metallic intermediates (prior to any electrophilic interception step), specifically the interactions involving the alkali metal, influence the regioselectivity of the Zn−H exchange process.

Oxidation of Carbon Monoxide Cocatalyzed by Palladium(0) and the H5PV2Mo10O40 Polyoxometalate Probed by Electron Paramagnetic Resonance and Aerobic Catalysis

The H(5)PV(2)Mo(10)O(40) polyoxometalate and Pd/Al(2)O(3) were used as co-catalysts under anaerobic conditions for the activation and oxidation of CO to CO(2) by an electron transfer-oxygen transfer mechanism. Upon anaerobic reduction of H(5)PV(2)Mo(10)O(40) with CO in the presence of Pd(0) two paramagnetic species were observed and characterized by continuous wave electron paramagnetic resonance (CW-EPR) and hyperfine sublevel correlation (HYSCORE) spectroscopic measurements. Major species I (65-70%) is assigned to a species resembling a vanadyl cation that is supported on the polyoxometalate and showed a bonding interaction with (13)CO. Minor species II (30-35%) is attributed to a reduced species where the vanadium(IV) atom is incorporated in the polyoxometalate framework but slightly distanced from the phosphate core. Under aerobic conditions, CO/O(2), a nucleophilic oxidant was formed as elucidated by oxidation of thianthrene oxide as a probe substrate. Oxidation reactions performed on terminal alkenes such as 1-octene yielded a complicated mixture of products that was, however, clearly a result of alkene epoxidation followed by subsequent reactions of the intermediate epoxide. The significant competing reaction was a hydrocarbonylation reaction that yielded a approximately 1:1 mixture of linear/branched carboxylic acids.

Cyclometalation of 6-Phenyl-2,2′-Bipyridine and Iridium: Synthesis, Characterization, and Reactivity Studies

Heating the potential tridentate 6-(4-R-phenyl)-2,2′-bipyridine ligand 1a (R = H), and derivatives 1b (R = CMe3) and 1c (R = OH), with IrCl3 hydrate in 2-methoxyethanol or acetone/H2O gave the unexpected bidentate cyclometalated NC dinuclear complexes [Ir(NC)Cl2(C5H5N)]2 (2a−cPy), as the major product. Altering the ligand/metal ratio from 1:1 to 2:1 produced a mixture of bis-cyclometalated complexes, Ir(NNC)(NC)Cl (3a,b), with tridentate and bidentate binding modes. Using discrete IrI synthons, such as Ir(dmso)3Cl or [Ir(cyclooctene)2Cl]2, gave a complicated mixture of products. However, when [Ir(C2H4)2Cl]2 was used, then the desired tridentate cyclometalated Ir(NNC) complex Ir(NNC)Et(C2H4)Cl (4) was synthesized cleanly. The dinuclear complex 2a-Py was converted to the corresponding mononuclear dichloride complexes Ir(NC)(NN)Cl2 (5a) upon refluxing with 4,4′-di-tert-butylbipyridine in N,N-dimethylacetamide (DMA). Treatment of 5a with ZnMe2 gives Ir(NC)(NNtBu)MeCl (6a). Abstraction of the chloride with AgOTF yields Ir(NC)(NNtBu)MeOTf (7a). Complex 7a undergoes stoichiometric CH activation with arenes and shows catalytic activity for the H/D exchange between benzene and (trifluoro)acetic acids.

Secondary organic aerosol formation from multiphase oxidation of limonene by ozone: mechanistic constraints via two-dimensional heteronuclear NMR spectroscopy

Because it is doubly unsaturated, gaseous limonene and ozone reactions exhibit considerable potential for not only a large quantity of secondary organic aerosol (SOA), but also a diverse and complicated product mixture influenced by reactant conditions. We explore the chemistry of limonene ozonolysis and provide evidence that under low-NOx conditions, the endocyclic double bond is oxidized in the gas phase, while under excess ozone conditions, the residual exocyclic double bond in condensed-phase products is heterogeneously oxidized by ozone. We use regular and multinuclear-multidimensional NMR spectroscopy, in particular 1D 1H-NMR, 1H,1H-COSY correlation spectroscopy, and 1H,13C-HSQC (heteronuclear single quantum coherence). For structural assignments we simulate 1H and 13C NMR spectra with ACDLabs online, relying representative products consistent with the postulated reaction mechanism. The 1-D 1H-NMR data allow us to quantify the extent to which the residual unsaturation is oxidized with rising ozone, confirming our hypothesis that the residual unsaturation is oxidized via heterogeneous uptake of ozone to fresh SOA particles.

The Implausibility of Metabolic Cycles on the Prebiotic Earth

Cycles occur widely in all branches of chemistry. The definition of a catalyst as an agent that facilitates the conversion of reactants to products without itself being changed almost guarantees that a catalyst can initiate successive “cycles” of the same reaction. Metabolic cycles are different. Strictly, they are by definition restricted to biochemistry. Like catalytic cycles, they too result in repeated conversions of substrates into products, but they involve much more complex sequences of chemical reactions. As far as I am aware, the formose reaction, which converts formaldehyde to a complicated mixture of products, including various sugars [1], is the only known nonenzymatic reaction sequence that is at all similar to a metabolic cycle, although the existence of one or two much simpler cycles has been established or made probable in the literature of prebiotic chemistry [2,3]. The possibility that reactions of hydrogen cyanide (HCN) might form the basis for a complex cyclic organization has been proposed [4], but there is as yet no experimental evidence to support this proposal.

1,2-Azaphosphol-5-ene Complexes through Metal-Assisted Synthesis

Thermal ring opening of {[2-bis(trimethylsilyl)methyl-3-phenyl-2H-azaphosphirene-κP]pentacarbon-yltungsten(0)} (1) in toluene in the presence of 1-piperidino carbonitrile (2) and various mono- and disubstituted alkenes, i.e., ethyl acrylate (4), E-stilbene (6), fumaronitrile (7), and maleic anhydride (10), was investigated. Special emphasis was placed on the dependence of the regio- and stereoselectivity of the transiently formed nitrilium phosphane-ylide complex 3 on the electronic properties of the alkenes. Three-component reaction of 1, 2, and 4 yielded regioselectively a 1:1 mixture of the diastereomeric 4-ethoxycarbonyl-substituted 1,2-azaphosphol-5-ene complexes 5a,b; the constitution of 5a was unambiguously established by single-crystal X-ray diffraction. Whereas E-stilbene (6) gave no reaction with complex 3, fumaronitrile (7) reacted with transient 3 to furnish the diastereomeric 1,2-azaphosphol-5-ene complexes 8a,b together with the 2H-1,3,2-diazaphosphole complex 9; the product ratio of 2:1:1 was determined by 31 P{ 1 H} NMR spectroscopy. Reaction of 1, 2, and maleic anhydride (10) resulted in a complicated product mixture, whereby the constitution of the spirocyclic complexes 11a,b (bearing a 1,3,2-oxazaphosphol-3-ene moiety) is based on their NMR data. Further examination showed that the C-O double bond system of 10 did not participate in a [3+2] cycloaddition reaction if the thermal decomposition of complex 1 was carried out in neat benzonitrile, thus showing the preference of the transiently formed C-phenyl-substituted nitrilium phosphane-ylide complex 12 for the C-C double bond of 6: In this case, the bicyclic complexes 13a,b were formed exclusively.

Formation of novel toxic compounds from oxidative interaction between salsolinol and cysteine

The electrochemically-driven oxidation of salsolinol (SAL) precedes via a 2e, 2H + process to produce the corresponding o-quinone (E) intermediate which has a very short lifetime and can be scavenged by cysteine to give the corresponding adduct cysteinyl salsoninol (F). F is more easily oxidized to the corresponding o-quinone (G) followed by cyclization resulting in the formation of the quinone imine intermediate (H). H can then undergo series of nucleophilic addition and oxidation reactions to produce a very complicated mixture of products including some dihydrobenzothiazines. Six of these products have been isolated and identified. Central administration of these compounds into laboratory mice revealed that three of them are fairly toxic and evoke profound behavioral responses.

Higher Nuclearity Fe,Ru Mixed-Metal Dicarbide Cluster Compounds Derived from Ethynediyldiiron Complex (η5-C5Me5)(CO)2Fe−C⋮C−Fe(η5-C5Me5)(CO)2

Reaction of the ethynyliron complexes FP−C⋮C−H [FP = Fp (1), Fp* (1*); Fp = (η5-C5H5)Fe(CO)2; Fp* = (η5-C5Me5)Fe(CO)2] with Ru3(CO)12 in refluxing benzene affords triruthenium μ-η1(Ru1):η2(Ru2):η2(Ru3)-acetylide cluster type compounds Ru3(CO)9[μ3-η1:η2:η2-C⋮C−FP] [FP = Fp (3), Fp* (3*)] in a manner similar to the reaction of 1-alkynes. In contrast to the clean reaction of 1 and 1*, reaction of the ethynediyldiiron complex, Fp*−C⋮C−Fp* (2*), gives a complicated mixture of products, from which Cp*2Fe2Ru2(μ4-C2)(CO)10 (5*) and Cp*2Fe2Ru6(μ6-C2)(CO)17 (6*) are isolated and characterized as permetalated ethene and permetalated ethane, respectively, by X-ray crystallography. It is revealed that the permetalated hydrocarbon structures in 5* and 6* are constructed via formal addition of a dimetallic species to the C−C triple bond in 2*. The octanuclear complexes 6* and 6 (Cp derivative) are also prepared by thermal dimerization of the tetranuclear FeRu3(μ-C2) core in 3* and 3. Higher nuclearity cluster compounds including the heptanuclear dicarbide cluster compound CpFeRu6(μ5-C2)(μ5-C2H)(CO)16 (12) and the heptanuclear bis(dicarbide) cluster compound Cp2Fe2Ru5(μ5-C2)2(CO)17 (15) are obtained not only by thermolysis but also by one-electron oxidation of the deprotonated anionic form of 3 (13).

Reactivity of "Eu(OiPr)2" with phenols: formation of linear Eu3, square pyramidal Eu5, cubic Eu8, and capped cubic Eu9 polymetallic europium complexes.

The direct reaction of europium with 2-propanol and phenols has been investigated under a variety of conditions. The reaction of europium metal with 2,6-dimethylphenol and 2,6-diisopropylphenol in 2-propanol at reflux revealed that polymetallic europium complexes could be generated by this method. Hx[Eu8O6(OC6H3Me2-2,6)12(OiPr)8], 1, and H5[Eu5O5(OC6H3iPr2-2,6)6(NCCH3)8], 2, were isolated by recrystallization in the presence of hexanes and acetonitrile, respectively, and characterized by X-ray crystallography. Complex 1 has a cubic arrangement of europium ions with face-bridging mu 4-O donor atoms, edge-bridging mu-O(phenoxide/phenol) ligands, and terminal O(isopropoxide/2-propanol) ligands. Complex 2 is mixed valent and has a square pyramidal europium core with four Eu(II) ions at the basal positions and one Eu(III) ion at the apex. Since these reactions gave complicated mixtures of products from which 1 and 2 could only be obtained in low yields, direct reactions under less forcing reaction conditions were investigated. Europium reacts slowly at room temperature to form arene-soluble divalent [Eu(OiPr)2(THF)x]n, 3. Complex 3 reacts with 2,6-dimethylphenol to form the arene-insoluble complex (H[Eu(OC6H3Me2)2(OiPr)])n, 4. Recrystallization of 4 in the presence of THF results in the crystallographically characterizable divalent trimetallic complex [Eu(OC6H3Me2-2,6)2(THF)2]3, 5, which has an unusual linear metal geometry. In the presence of HOiPr at ambient conditions in the glovebox, crystals of 5 slowly convert to the mixed valent H10[Eu8O8(OC6H3Me2-2,6)10(OiPr)2(THF)6], 6, which was found to have a cubic arrangement of europium atoms similar to 1 by X-ray crystallography. Complex 4, upon heating under vacuum, followed by reaction with THF, forms the arene-soluble divalent complex H18([Eu9O8(OC6H3Me2-2,6)10(THF)7][Eu9O9(OC6H3Me2-2,6)10(THF)6]), 7, which contains two types of capped cubic arrangements of europium ions in the solid state.