Radical Reactivity of the Biradical [⋅P(μ-NTer)2P⋅] and Isolation of a Persistent Phosphorus-Cantered Monoradical [⋅P(μ-NTer)2P-Et]

The activation of C−Br bonds in various bromoalkanes by the biradical [⋅P(μ-NTer)₂P⋅] ( 1 ) (Ter=2,6-bis-(2,4,6-trimethylphenyl)-phenyl) is reported, yielding trans-addition products of the type [Br−P(μ-NTer)₂P−R] ( 2 ), so-called 1,3-substituted cyclo-1,3-diphospha-2,4-diazanes. This addition reaction, which represents a new easy approach to asymmetrically substituted cyclo-1,3-diphospha-2,4-diazanes, was investigated mechanistically by different spectroscopic methods (NMR, EPR, IR, Raman); the results suggested a stepwise radical reaction mechanism, as evidenced by the in-situ detection of the phosphorus-centered monoradical [⋅P(μ-NTer)₂P-R].< To provide further evidence for the radical mechanism, [⋅P(μ-NTer)₂P-Et] ( 3Et ⋅) was synthesized directly by reduction of the bromoethane addition product [Br-P(μ-NTer)₂P-Et] ( 2 a ) with magnesium, resulting in the formation of the persistent phosphorus-centered monoradical [⋅P(μ-NTer)₂P-Et], which could be isolated and fully characterized, including single-crystal X-ray diffraction. Comparison of the EPR spectrum of the radical intermediate in the addition reaction with that of the synthesized new [⋅P(μ-NTer)₂P-Et] radical clearly proves the existence of radicals over the course of the reaction of biradical [⋅P(μ-NTer)₂P⋅] ( 1 ) with bromoethane. Extensive DFT and coupled cluster calculations corroborate the experimental data for a radical mechanism in the reaction of biradical [⋅P(μ-NTer)₂P⋅] with EtBr. In the field of hetero-cyclobutane-1,3-diyls, the demonstration of a stepwise radical reaction represents a new aspect and closes the gap between P-centered biradicals and P-centered monoradicals in terms of radical reactivity.     

Regioselective 1,2-Addition of Ti(IV)-enolate to α, β–Unsaturated Compounds

The nucleophilic addition to α, β-unsaturated carbonyl compounds is a fundamental C-C bond forming reaction in organic chemistry1. Since there are two reaction sites in the α, β–unsaturated carbonyl group, the regioselectivity of the nucleophilic addition (1, 2 vs. 1, 4 addition) is of primary importance when applying this type of reaction in organic synthesis. Factors that control the regioselectivity include the softness and hardness of the attacking nucleophiles2, solvent and temperatu…     

Influence of Saturated or Unsaturated Dicarboxylate Anions on Magnetism of Co(Ⅱ) and Cu(Ⅱ) Hydroxide-based Spin Layers

In the context of molecule-based magnets, a driving force is the design of complex systems, combining molecular units used as building blocks, to favor bulk magnetic properties. Such a strategy has been successfully explored for the preparation of both purely organic as well as purely inorganic magnets. A step forward, to achieve multifunctional solids, is the combination of both the molecular and inorganic chemistries to build hybrid organic/inorganic materials. Clearly, such an approach is very appealing for the design of novel 3d materials exhibiting improved properties with respect to those of the individual networks.     

Reactivity of the bridged-sulfide complex Pd2Cl2(μ-S)(μ-dmpm)2 toward electrophiles

The dipalladium(I) complex Pd(2)Cl(2)(dmpm)(2) (1a) [dmpm = bis(dimethylphosphino)methane] is known to react with elemental sulfur (S(8)) to give the bridged-sulfide complex Pd(2)Cl(2)(μ-S)(dmpm)(2) (2a) but, in the presence of excess S(8), PdCl(2)[P,S-dmpm(S)] (4a) and dmpm(S)(2) are generated. Treatment of 1a with elemental selenium (Se(8)), however, gives only Pd(2)Cl(2)(μ-Se)(dmpm)(2) (3a). Complex 4a is best made by reaction of trans-PdCl(2)(PhCN)(2) with dmpm(S). Complex 2a reacts with MeI to yield initially Pd(2)I(2)(μ-S)(dmpm)(2) and MeCl, and then Pd(2)I(2)(μ-I)(2)(dmpm)(2) and Me(2)S, whereas alkylation of 2a with MeOTf generates the cationic, bridged-methanethiolato complex [Pd(2)Cl(2)(μ-SMe)(dmpm)(2)]OTf (5). Oxidation of 2a with m-CPBA forms a mixture of Pd(2)Cl(2)(μ-SO)(dmpm)(2) and Pd(2)Cl(2)(μ-SO(2))(dmpm)(2), whereas Pd(2)Br(2)(μ-S)(dmpm)(2) reacts selectively to give Pd(2)Br(2)(μ-SO)(dmpm)(2) (6b). Treatment of the Pd(2)X(2)(μ-S)(dmpm)(2) complexes with X(2) (X = halogen) removes the bridged-sulfide as S(8), with co-production of Pd(II)(dmpm)-halide species. X-ray structures of 3a, 5 and 6b are presented. Reactions of dmpm with S(8) and Se(8) are clarified. Differences in the chemistry of the dmpm systems with that of the corresponding dppm systems [dppm = bis(diphenylphosphino)methane] are discussed.     

Gas-Phase Reactivity of Peptide Thiyl (RS•), Perthiyl (RSS•), and Sulfinyl (RSO•) Radical Ions Formed from Atmospheric Pressure Ion/Radical Reactions

In this study, we demonstrated the formation of gas-phase peptide perthiyl (RSS?) and thiyl (RS?) radical ions besides sulfinyl radical (RSO?) ions from atmospheric pressure (AP) ion/radical reactions of peptides containing inter-chain disulfide bonds. The identity of perthiyl radical was verified from characteristic 65 Da (?SSH) loss in collision-induced dissociation (CID). This signature loss was further used to assess the purity of peptide perthiyl radical ions formed from AP ion/radical reactions. Ion/molecule reactions combined with CID were carried out to confirm the formation of thiyl radical. Transmission mode ion/molecule reactions in collision cell (q2) were developed as a fast means to estimate the population of peptide thiyl radical ions. The reactivity of peptide thiyl, perthiyl, and sulfinyl radical ions was evaluated based on ion/molecule reactions toward organic disulfides, allyl iodide, organic thiol, and oxygen, which followed in order of thiyl (RS?) > perthiyl (RSS?) > sulfinyl (RSO?). The gas-phase reactivity of these three types of sulfur-based radicals is consistent with literature reports from solution studies.      

Radical/Iminium Domino Strategy (RIDS) for Rapid Construction of Sterically Congested γ-Lactam-Based Multiheterocycles

Cu-Catalyzed radical/iminium domino strategy (RIDS) for the efficient synthesis of quaternary-carbon-containing γ-lactam-based multiheterocyclic structures from α-bromocarboxamides is reported. This domino reaction strategy enables the construction of multiheterocycles in one step. Mechanistic studies showed that two catalytically generated iminiums are likely to be key intermediates in the catalytic cycle. The developed method can be used in a chemoselective manner to produce multicyclic products in the reaction with ketones possessing two different carbonyls.     

Reactivity of the Unsaturated Triosmium Cluster [Os3(CO)8{Ph2PCH2P(Ph)C6H4}(μ-H)] with Thiols

The reaction of the unsaturated cluster [(-H)Os₃(CO)₈{Ph₂PCH₂P(Ph)C₆H₄}] 2 with C₂H₅SH, CH₃CH(CH₃)SH and C₆H₅SH are reported. The reaction of 2 with C₂H₅SH yields the new complexes [Os₃(CO)₈(-SC₂H₅)(¹-SC₂H₅){Ph₂PCH₂P(Ph)C₆H₄}(-H)] 9 and [Os₃(CO)₈)(SC₂H₅)(Ph₂PCH₂P)(Ph)C₆H₄}] 8 in 24 and 57% yields respectively and the known compound [(Os₃(CO)₈)(-SC₂H₅)(-dppm)(-H)] 7 in 5% yield. Compound 9, which exists as two isomers in solution, converts into 8 almost quantitatively in solution at 25°C and more rapidly in refluxing hexane. Compound8 reacts with H₂ at 110°C to give 7 in high yield (86%). Treatment of 2 with propane-2-thiol yields [Os₃(CO)₈{-SCH(CH₃)CH₃}{Ph₂PCH₂P(Ph)C₆H₄}] 10 and [(Os₃(CO)₈{-SCH(CH₃)CH₃}{¹-SCH(CH₃)CH₃}{Ph₂PCH₂P(Ph)C₆H₄}(-H)] 11 in 75 and 3% yields respectively while with C₆H₅SH, [(Os₃(CO)₈(-SC₆H₅)(-dppm)(-H)] 6 is obtained as the only product in 75% yield. In both 8 and 10, the thiolato ligand bridges the Os–Os edge which is also bridged by the metallated phenyl group. The new compounds have been characterized by elemental analyses and spectroscopic methods (IR, ¹H and ³¹P NMR). The molecular structures of 7, 8, 9 and 10 are reported as determined by X-ray diffraction studies.     

Reactivity of the heteronuclear cluster RuOs3(μ-H)2(CO)13 with indene

The heteronuclear cluster RuOs₃(μ-H)₂(CO)₁₃ (1) reacts with indene under thermal activation to afford the novel clusters RuOs₃(μ-H)(CO)₉(μ-CO)₂(η⁵-C₉H₇) (3), RuOs₃(μ-H)(CO)₉(μ₃,η⁵:η²:η²-C₉H₇) (4) and Ru₂Os₃(μ-H)(CO)₁₁(μ₃,η⁵:η²:η²-C₉H₇) (5), the latter two possessing indenyl ligands in the μ₃,η⁵:η²:η² bonding mode. Cluster 5 exists as a mixture of two isomers. The inter-relationship among the clusters has also been investigated.     

Controlled/“Living “Radical Polymerization of(-)-Menthyl Methacrylate

The atom transfer radical polymerization(ARP)of (-)-menthyl methacrylatc((-)-MnMA) mediated by CuCl/bipyridine and ethy1 2-bromopropionate or 1-phenylethyl bromide in THF system has been studied.The dependence of the specific rotation on molecular weight and the CD of Poly((-)-MnMA) thus obatined was investigated.     

Rational Design of Fe2(μ-PR2)2(L)6 Coordination Compounds Featuring Tailored Potential Inversion

It was recently discovered that some redox proteins can thermodynamically and spatially split two incoming electrons towards different pathways, resulting in the one-electron reduction of two different substrates, featuring reduction potential respectively higher and lower than the parent reductant. This energy conversion process, referred to as electron bifurcation, is relevant not only from a biochemical perspective, but also for the ground-breaking applications that electron-bifurcating molecular devices could have in the field of energy conversion. Natural electron-bifurcating systems contain a two-electron redox centre featuring potential inversion (PI), i. e. with second reduction easier than the first. With the aim of revealing key factors to tailor the span between first and second redox potentials, we performed a systematic density functional study of a 26-molecule set of models with the general formula Fe₂(μ-PR₂)₂(L)₆. It turned out that specific features such as i) a Fe−Fe antibonding character of the LUMO, ii) presence of electron-donor groups and iii) low steric congestion in the Fe's coordination sphere, are key ingredients for PI. In particular, the synergic effects of i)-iii) can lead to a span between first and second redox potentials larger than 700 mV. More generally, the “molecular recipes” herein described are expected to inspire the synthesis of Fe₂P₂ systems with tailored PI, of primary relevance to the design of electron-bifurcating molecular devices.     

Free Radical Cyclization of 1,3‐Dicarbonyl Compounds Mediated by Manganese(III) Acetate with Alkynes and Synthesis of Tetrahydrobenzofurans,Naphthalene, and Trifluoroacetyl Substituted Aromatic Compounds

Furan derivatives were obtained from radical cyclizations of 1,3‐dicarbonyl compounds mediated by Mn(OAc)₃ with phenyl acetylene 2a (14–66% yields). Naphthalene derivates 4a and 4b were produced in the treatments with 2a. In addition to these, trifluoroacetyl substituted naphthalene 4c, benzofuran 4d, and benzothien 4e were obtained in the reactions of trifluoromethyl‐1,3‐dicarbonyls (1 g–i) with 2a.     

Activation of propargylic alcohols by dimolybdenum tris(μ-thiolate) complexes: Influence of the substituents R in HCCCR2(OH)-vinylidene/allenylidene transformation. Reactivity of allenylidene complexes

Reaction of the bis(nitrile) complex [Mo₂Cp₂(μ-SMe)₃(NCMe)₂](BF₄) (1) with dimethylpropargylic alcohol, HCCCMe₂(OH), at room temperature in dichloromethane produced good yields of the μ-alkynol species [Mo₂Cp₂(μ-SMe)₃{μ-CHCCMe₂(OH)}](BF₄) (2a) through replacement of the two acetonitrile ligands in 1 by the alkynol. The NMR spectra of 2a indicate a μ-η¹:η¹ coordination mode for the alkyne which is thereby incorporated into a dimetallacyclobutene ring like that found here by X-ray diffraction (XRD) analysis of the related complex [Mo₂Cp₂(μ-SMe)₃(μ-η¹:η¹-CHCCO₂Me)](BPh₄) (2b). When 2a was stirred with Et₃N at room temperature in dichloromethane, deprotonation gave high yields of the μ-3-hydroxyalkynyl derivative [Mo₂Cp₂(μ-SMe)₃{μ-η¹:η²-CCCMe₂(OH)}] (3), together with small amounts of the already-known vinylacetylide [Mo₂Cp₂(μ-SMe)₃{μ-η¹:η²-CCC(Me)CH₂}] (4) resulting from dehydration of 3. Treatment of 3 with 1 equiv. of HBF₄ · OEt₂ in diethyl ether at room temperature gave the 3-hydroxyvinylidene derivative [Mo₂Cp₂(μ-SMe)₃{μ-η¹:η²-CCHCMe₂(OH)}](BF₄) (5) as the major product, together with other minor products [Mo₂Cp₂(μ-SMe)₃{μ-η¹:η²-CCHC(Me)CH₂}](BF₄) (6), [Mo₂Cp₂(μ-SMe)₃(μ-η¹:η²-CCCMe₂)](BF₄) (7), [Mo₂Cp₂(μ-SMe)₃(μ-η¹:η²-CCH₂)](BF₄) (8), [Mo₂Cp₂(μ-SMe)₃{μ-η¹:η²-CCH(CHMe₂)}](BF₄) (9) and [Mo₂Cp₂(μ-SMe)₃(μ-O)](BF₄) (10). The vinylidene (6) and allenylidene (7) species resulted from dehydration of the 3-hydroxyvinylidene complex 5 whereas the vinylidene derivative 8 was formed by deketonisation of 5. When 3 reacted with a large excess of HBF₄ · OEt₂ in dichloromethane, the 3-isopropylvinylidene complex 9 was obtained nearly quantatively via a H radical process. When left for several days CD₂Cl₂ solutions of 5 afforded mainly the vinylidene species 8 by deketonisation and the side-oxoproduct [Mo₂Cp₂(μ-SMe)₃(μ-O)](BF₄) (10) by hydrolysis or reaction with oxygen. Addition of nucleophiles (H⁻, OMe⁻, OH⁻, SMe⁻) to the allenylidene complex [Mo₂Cp₂(μ-SMe)₃(μ-η¹:η²-CCCPh₂)](BF₄) (11) resulted in the formation of the corresponding μ-acetylide derivatives [Mo₂Cp₂(μ-SMe)₃(μ-η¹:η²-CCCRPh₂)] [R = H (12), OMe (16a), OH (17), SMe (16b)], which by further reaction with tetrafluoroboric acid afforded either the vinylidene species [Mo₂Cp₂(μ-SMe)₃{μ-η¹:η²-CCH(CRPh₂)}](BF₄) when R = H (13), or the starting complex 11 when R is a leaving group (OMe). Reaction of 13 with Na(BH₄) gave the μ-alkylidyne complex [Mo₂Cp₂(μ-SMe)₃(μ-η¹-CCH₂CPh₂H)] (14) by nucleophilic attack of H⁻ at the C_β carbon atom of the vinylidene chain. Proton addition at C_α in 14 led to the formation of a μ-vinylidene compound 15 containing an agostic C-H bond. New complexes have been characterised by elemental analyses and spectroscopic methods, supplemented for 2b and 3 by X-ray diffraction studies.     

Synthesis of 1-(2''''-Phenyl)cyclopropyl-2,3-epoxypropan-1-ol as the Radical Precursor for the Kinetic Study of Oxiranylcarbinyl Radical

The oxiranylcarbinyl radical can undergo rapid rearrangement to generate an allyloxy radical (1 2)1. This process has been found application in organic synthesis2. For example, Rawal developed a novel method leading to cis-fused bicyclic compounds based on tandem reactions of oxiranylcarbinyl radical ring opening - intramolecualr H abstraction - radical addition2f. OOk1k-112 On the other hand, the oxiranylcarbinyl radical rearrangement is so rapid that this radical species has never be…     

Development of a micro-total analysis system (μ-TAS) for the determination of catecholamines

In this study, the first micro-total analysis system (μ-TAS) for catecholamines (dopamine, epinephrine, and norepinephrine) analysis in which preconcentration, separation, and determination steps were integrated on a microchip was developed. Electrophoresis microchips in a variety of channel lengths and designs were produced in borofloat glass for the μ-TAS studies. Chambers for the preparation of monolithic disks were formed in the microchips at the intersection of the injection and separation channels. Vinyl phenylboronic acid–ethylene glycol dimethacrylate polymers were prepared as monolithic disks in these chambers with a depth of 0.05 mm and a diameter of 2.1 mm. The microchips could be used more than 50 times if mechanical problems such as plugging or fracturing did not occur. Adsorption and elution of catecholamines were realized electrokinetically, with catecholamines determined via laser-induced native fluorescence detection following elution and electrophoretic separation. The most promising results were obtained with 100 mM phosphate buffer (pH 2) for elution with 25% propanol added to the separation buffer (100 mM phosphate, pH 3).     

Reactivity of the heteronuclear cluster Cp*IrOs3(μ-H)2(CO)10 with some group 16 substrates

The mixed metal cluster Cp*IrOs₃(μ-H)₂(CO)₁₀ (1) reacted readily with a number of group 16 substrates under chemical activation with TMNO. It reacted with C₆H₅SH to afford the novel cluster Cp*IrOs₃(μ-H)₃(CO)₉(μ-SPh) (2). It also reacted readily with Ph₃PSe to afford five new clusters, viz., Cp*IrOs₃(μ-H)₂(CO)₉(μ₃-Se) (3) Os₃(μ-H)₂(CO)₇(μ₃-Se)(PPh₃)₂ (4), Cp*IrOs₃(μ-H)₂(CO)₉(PPh₃) (5), Cp*IrOs₃(μ-H)₂(μ₃-Se)(CO)₈(PPh₃) (6) and Cp*IrOs₃(μ-H)₂(μ₃-Se)₂(CO)₇(PPh₃) (7). The reaction pathway for this reaction has been studied carefully and suggests that Ph₃PSe functioned primarily as a selenium atom transfer agent to give initially the even more reactive 3. The reaction of 1 with di-p-tolyl ditelluride yielded three new clusters, 8-10, which were non-interconverting stereoisomers with the formulation Cp*IrOs₃(μ-H)₂(μ-Te-p-C₆H₄CH₃)₂(CO)₈.     

N-Chlorosuccinimide(NCS):A Novel Initiator for Atom Transfer Radical Polymerization of Methyl Methacrylate

Atom transfer radical polymerization （ATRP） of methyl methacrylate （MMA） was achieved, using N-chlorosuccinimide （NCS） as an initiator together with catalytic system CuCl/PMDETA （N,N,N＇,N＇,N＂-pentamethyldiethylenetriamine）, CuCl/MA5-DETA （N,N＇,N＇,N＂-penta（methylacrylate）diethylenetriamine）, and CuCl/bipy （bipy= 2,2＇-bipyridyl） respectively. The results indicated that the polymerization possessed typical controlled/living radical polymerization characteristics. The analysis for terminal group of obtained polymer by ^1H NMR proved that NCS is an initiator for ATRP. In comparison with NBS, the polymerization rate was slower and the resulted polymer had narrower molecular weight distribution （MWD） when NCS was employed as the initiator.     

The X-ray Structure, Electrochemistry and Catalytic Reactivity of Os4Au(μ-H)3(CO)12(PPh3) Towards the Oxidative Carbonylation of Aniline

The reaction of the anion [Os₄(-H)₃(CO)₁₂]^– with one equivalent of Au(PPh₃)Cl affords [Os₄Au(-H)₃(CO)₁₂(PPh₃)] (1), the structure of which was established by single crystal X-ray analysis. Its electrochemical behavior and catalytic properties are also reported. This bimetallic cluster catalyses the oxidative carbonylation of aniline to give methyl phenylcarbamate in methanol with good conversion and selectivity compared to the homometallic [Os₄(-H)₄(CO)₁₂] cluster.     

Electron Spin Resonance (ESR) Spectroscopy of the Transition-Metal Complexes and Clusters Ⅰ.Systematic Investigations of Real-and Complex-Orbital Methods for Calculating the d-Orbital Energies of a Low-Spin(S=1/2)nd~5(t_2~5,~2T_2

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