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Here we disclose a sulfurane-mediated method for the formation of dimeric dibenzofuran helicenes via the reaction between diaryl sulfoxides and hexadehydro-Diels-Alder (HDDA) derived benzynes. A variety of S-shaped and U-shaped helicenes were formed under thermal conditions. Both experimental and DFT studies support a sulfur(IV)-based coupling (aka ligand coupling) mechanism involving tetracarbo-ligated S(IV) intermediates undergoing reductive elimination to afford the helicene products. This process involves the de novo generation of five new rings in a single operation and constitutes a new method for the construction of topologically interesting, polycyclic aromatic compounds.

Aryllithiums are one of the most common and important aryl nucleophiles; nevertheless, methods for arylation of aryllithums to produce biaryls have been limited. Herein, we report arylation of aryllithiums with S-arylphenothiazinium ions through selective ligand coupling of intermediary sulfuranes. Various unsymmetrical biaryls could be obtained without transition-metal catalysis.

A transition metal-free one-pot stereoselective approach to substituted (E,Z)-1,3-dienes was developed by using an interrupted Pummerer reaction/ligand-coupling strategy. Readily available benzothiophene S-oxides, which can be conveniently prepared by oxidation of the parent benzothiophenes, undergo Pummerer coupling with styrenes. Reaction of the resultant sulfonium salts with alkyllithium/magnesium reagents generates underexploited hypervalent sulfurane intermediates that undergo selective ligand coupling, resulting in dismantling of the benzothiophene motif and the formation of decorated (E,Z)-1,3-dienes.

The reaction of Re(CO)5Cl with 4-mercaptopyridine (4-PySH) led to the formation of [Re(CO)3(4-HPyS)3]Cl (1), showing three hydrogen-bonding donors of 4-PySH ligands as well as a characteristic liga...

An S-selective arylation of pyridylsulfides with good functional group tolerance has been developed. The resulting pyridylsulfonium salts have been used in a scalable transition metal-free coupling protocol yielding functionalized bipyridine scaffolds with extensive functional group tolerance and modularity. Pyridylsulfonium salts were coupled to lithiated pyridines in a sulfur-mediated synthesis of bipyridines. This modular methodology, permits selective introduction of functional groups from commercially available pyridyl halides, furnishing symmetrical and unsymmetrical 2,2’- and 2,3’-bipyridines. Iterative application of the methodology enabled the synthesis of a functionalized terpyridine with three different pyridine components.

The structures and energetics of the cyclopentadienyliron carbonyl boronyls Cp2Fe2(BO)2(CO)n (n = 3, 2, 1, 0) have been examined by density functional theory. The lowest energy Cp2Fe2(BO)2(CO)n (n = 2, 0) structures are found to have bridging dioxodiborene (µ-B2O2) ligands that can exist as cis or trans stereoisomers. Either µ-B2O2 stereoisomer functions as a net three-electron donor to each iron atom in such binuclear complexes. The lowest energy Cp2Fe2(BO)2(CO)n (n = 3, 1) structures resemble their isoelectronic Cp2Mn2(CO)n+2 analogues. Thus the lowest energy Cp2Fe2(BO)2(CO)3 structure consists of two CpFe(BO)(CO) units joined by an Fe–Fe bond bridged by a CO group. The lowest energy Cp2Fe2(BO)2(CO) structure is a singlet triply bridged structure with a short ∼2.17 A Fe Fe distance suggesting a formal triple bond. This latter structure is very similar to the experimental structure of the isoelectronic Cp*2Mn2(µ-CO)3, synthesized by Hermann and coworkers and shown by X-ray crystallography to be a triply bridged structure with a ∼2.17 A Mn Mn distance.

By treating Tp'W(CO)(HCCH)(NCHCH3) with iodine, a 1 e− oxidation of the metal complex occurs leading to radical coupling through the β-carbons of two 1-azavinylidene ligands. Formation of the diimido bridged dimer [(Tp'W(CO)(HCCH))2(μ-NCH(CH3)CH(CH3)N)][I3]2 occurs diastereoselectively; only the S,S,R,R diastereomer is isolated. An inversion center is located at the center of the bridge C-C bond, leading to identical spectroscopic signals for each end of the dimer. A second order splitting pattern, A3XA3′X′, characterizes the bridge protons in the 1H NMR spectrum. As a result of one electron oxidation of the monomer followed by ligand coupling, each metal center is oxidized from tungsten (II) to tungsten (IV), d4 to d2, leading to a high carbonyl stretching frequency of 2116 cm−1 in the IR spectrum of the dicationic product.

Distinct approaches to synthesize bis-azine biaryls are in demand as these compounds have multiple applications in the chemical sciences and are challenging targets for metal-catalyzed cross-coupling reactions. Most approaches focus on developing new reagents as the formal nucleophilic coupling partner that can function in metal-catalyzed processes. We present an alternative approach using pyridine and diazine phosphines as nucleophilic partners and chloroazines where the heterobiaryl bond is formed via a tandem SNAr-phosphorus ligand-coupling sequence. The heteroaryl phosphines are prepared from chloroazines and are bench stable solids. Using this strategy, a range of bis-azine biaryls can be formed from abundant chloroazines that would be challenging using traditional approaches and a one-pot cross-electrophile coupling of two chloroazines is feasible.

The ligand coupling reaction (LCR) of hypervalent pentacoordinate antimony compounds (ArnTol5−nSb; Ar = p-trifluoromethylphenyl, Tol = p-methylphenyl; n = 0–5) was analyzed via the long-range-corre...

A μ-oxo-linked subphthalocyanine (SubPc)-tetrabenzotriazacorrole (TBC)-SubPc triad has been synthesized. The desired triad could be formed using axial ligand coupling between a TBC phosphorus(V) complex and SubPc, and was characterized by MS, 1H and 31P NMR spectra. The triad can absorb light across the entire UV-vis region. Spectroscopic and theoretical analyses support the proposal that the TBC chromophore interacts with the SubPc chromophore.

The synthesis of 2-sulfinyl oxetanes is described by a C–C bond-forming cyclisation strategy. Oxetanes bearing electron-poor aryl sulfoxides are shown to be viable targets using this strategy. We report investigations into the sulfoxide magnesium exchange on 2-sulfinyl oxetanes, which resulted in products formed via ligand exchange and ligand coupling pathways. The sulfinyl oxetanes can be readily oxidised to the sulfonyl oxetanes.

Sandwich structures formed by metal atoms intercalated between sp(2)-carbon planes can be found either in metal-graphite-based materials or discrete multinuclear sandwich complexes. Their reactivity, and in particular their dynamic behaviour, has recently attracted interest both from a structural and a practical aspect, for example in catalysis. However, progress in this area has been rather slow, and it remains difficult to elucidate their structure and behaviour at the molecular level. Here, we report two sandwich complexes--in which four palladium centres are incorporated between two π-conjugated ligands--which exhibit two modes of redox-switchable structural changes. In the first complex, the tetrapalladium chain is split by oxidation into two well-separated dipalladium units. This motion is reversed on reduction. In the second complex, reversible carbon-carbon coupling occurs between the ligands during the redox process.

[Cp*Ru(μ-NHPh)]2 (Cp* = η5-C5Me5) reacted with CO, t-BuNC, Ph2S═CH2, or Me3SiC≡CH to give the dinuclear ruthenium bridging imido complexes [(Cp*Ru)2(μ-NPh)(μ-L)] (2a, L = CO; 2b, L = t-BuNC; 2c, L = CH2; 2d, L = CCHSiMe3). Protonolysis of 2d with t-BuOH produced the parent vinylidene complex [(Cp*Ru)2(μ-NPh)(μ-CCH2)] (2e). Treatment of 2e with HOTf or MeOTf afforded the cationic alkylidyne complexes [(Cp*Ru)2(μ-NPh)(μ-CR)]OTf (2f, R = Me; 2g, R = Et). Hydride abstraction from 2c with Ph3CBF4 gave the methylidyne complex [(Cp*Ru)2(μ-NPh)(μ-CH)]BF4 (2h). X-ray structures of 2a−c and 2f revealed short Ru−N distances (1.876−1.894 A) consistent with Ru−N multiple bonds, and the μ-alkylidyne 2f also featured short Ru−C bonds (1.929(7) and 1.914(7) A). In addition to giving simple Lewis base adducts such as [(Cp*Ru)2(μ-NPh)(μ-CO)(PMe3)] and [(Cp*Ru)2(μ-NPh)(μ-CH2)(t-BuNC)2], these imido complexes provided an array of novel ligand coupling reactions. Thus, 2b underwent a tandem imido−isocyanide coupling and C−H a...

To prevent the occurrence of dialysis-related amyloidosis, an immunoadsorption wall based on polyacrylamide has been manufactured by a recently developed, partially incomplete, two-stage polymerization method. During the preparation process, efficient utilization of coupling antibodies is the key to large-scale production of such a toxin removal modality. In this study, we attempted to carry out the ligand coupling procedure after formation of a cyanogen bromide (CNBr)-activated stationary phase, using anti-beta2-microglobulin (beta-2M) antibodies. In vitro immunoadsorption tests show that the levels of beta-2M decrease rapidly within the first 2 hours for all the immunoadsorption tests. After that, nearly blank values were reached for tests of initial levels of c. 30 microg/mL and c. 82 microg/mL, whereas a relatively constant level of c. 10 microg/mL was maintained for the test of initial levels of c. 185 microg/mL. The maximum surface binding capacity of the prepared immunoadsorption walls is estimated by fitting experimental data, using a mathematical model of saturation kinetics. The present comparative investigation also suggests the manufacturing process for an immunoadsorption wall could be improved and facilitated by this new ligand coupling procedure without compromising the resulting binding capacity. Furthermore, the experimental protocols as well as the present methodology could be helpful for development of a clinically applicable immunoadsorption wall.

The synthesis of 2-sulfinyl oxetanes is described by a C–C bond-forming cyclisation strategy. Oxetanes bearing electron-poor aryl sulfoxides are shown to be viable targets using this strategy. We report investigations into the sulfoxide magnesium exchange on 2-sulfinyl oxetanes, which resulted in products formed via ligand exchange and ligand coupling pathways. The sulfinyl oxetanes can be readily oxidised to the sulfonyl oxetanes.

π-Allyl (η3-C3H5), a four-electron donor, was used as a ligand model to replace η5-C5Me4SiMe3 in DFT calculations on the tetranuclear yttrium polyhydrido complex (η5-C5Me4SiMe3)4Y4H8 containing a Y4H8 tetrahedral core structure, which may separate the four π-allyl groups and hence suppress the allyl ligand coupling during the computation. In terms of the calculated core geometry, isomerization energy barrier, charge population, and frontier orbital features of the complex, the η3-C3H5 ligand model is comparable to η5-C5H5. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007

The reaction of TiCl4(THF)2 or ZrCl4(THF)2 with Mg in the presence of 1-aza-1,3-dienes (1) has been investigated. Reduction of TiCl4(THF)2 with 2 equiv of Mg in the presence of 2 equiv of (R1)NCHC(R2)CH(Ph) yields the first homoleptic 1-aza-1,3-diene complex, [Ti{N(R1)CHC(R2)CH(Ph)}2] (7), but only if the 1-aza-1,3-diene is substituted by a sterically demanding group at the nitrogen atom (1b: R1 = C6H3-2,6-iPr2, R2 = H). X-ray crystallography indicates a σ2,π coordination of the heterodienes, which are reduced to 1-azabut-2-ene-1,4-diyl dianions to form folded 1-aza-2-titanacyclopent-4-ene rings. As a byproduct, the bicyclic complex [{N(R1)CHC(R2)CH(Ph)}Ti{N(R1)CHC(R2)CH(Ph)CH{C(R2)CH(Ph)}N(R1)] (8) was isolated, which is believed to arise from CN insertion of 1b into the Ti−C bond of the intermediate [{N(R1)CHC(R2)CH(Ph)}TiCl2], followed by the coordination of a further 1-aza-1,3-diene ligand. The analogous bicyclic zirconium complex [{N(R1)CHC(R2)CH(Ph)}Zr{N(R1)CHC(R2)CH(Ph)CH{C(R2)CH(Ph)}N(R1)] (6: R...

Divalent silicon species bearing an 8-amino- or 8-phosphino-1-naphthyl group have been shown to behave as nucleophilic sila-ylides in the presence of diphenylacetylene to afford zwitterionic intermediates containing alkenyl anion and ammonium or phosphonium cation moieties. The reaction pathways of these zeitterionic intermediates have been clarified to be highly dependent on the character of the cationic center such as N and P.

By taking advantage of solvothermal reactions of Re2(CO)10 with 2-mercaptobenzothiazol (HNS2) or 2-mercaptobenzoxazol (HNOS), a series of Re(I) complexes (1–4) with in situ ligands were synthesized and structurally characterized by X-ray diffraction. In this study, we examined the effects of reaction conditions (i.e., reaction solvents and temperatures) on the HNS2 system to give complexes 1–3, and also compared the reaction products of the HNS2 (2) and HNOS (4) systems under similar reaction conditions. For the HNS2 system, the reaction temperatures at 140 and 120 °C in mesitylene led to different ligands in complexes 1 and 2, respectively. However, at the same temperature of 140 °C, different solvents (mesitylene or benzene) caused the formation of complexes 1 and 3 containing different ligands, respectively. Although the same temperature and solvent were used, HNS2 and HNOS underwent a similar in situ ligand reaction in dinuclear complexes 2 and 4, which surprisingly show both anti and syn conformations, respectively.

The reaction of 4-methoxycarbonylchroman-3-one with aryllead triacetates gave the 4-aryl derivatives after 3-4 h reaction times in moderate to good yields. Unexpectedly, 2,4-diarylated derivatives were also obtained after longer reaction times. The activating methyl ester group proved difficult to remove by standard decarboxylation procedures. 4-Benzyloxycarbonylchroman-3-ones were therefore prepared and reacted with aryllead triacetates to afford the corresponding 4-aryl derivatives. These were subsequently decarboxylated, reduced and dehydrated to afford neoflavenes in modest overall yields.

The presence of aryl radical species in the course of arylation reactions with tri and pentavalent organobismuth compounds has been studied by the use of an internal-trap containing reagent: tris(2-allyloxyphenyl)bismuth and its diacetate. The intervention of radical species can be excluded in C - and O -arylation under basic conditions as well as in copper catalyzed O - and N -arylation, as cyclized products were never detected in any of these reactions.