Vanadium(III) complexes containing phenoxy–imine–thiophene ligands: Synthesis,characterization and application to homo‐ and copolymerization of ethylene

A set of vanadium(III) complexes, namely {SNO}VCl₂(THF)₂ ( 2a , SNO = thiophene‐(N═CH)‐phenol; 2b , SNO = 5‐phenylthiophene‐(N═CH)‐phenol; 2c , SNO = 5‐phenylthiophene‐(N═CH)‐4‐tert ‐butylphenol; 2d , SNO = 5‐methylthiophene‐(N═CH)‐phenol; 2e , SNO = 5‐methylthiophene‐(N═CH)‐4‐tert ‐butylphenol; 2f , SNO = 5‐methylthiophene‐(N═CH)‐2‐methylphenol; 2g , SNO = 5‐methylthiophene‐(N═CH)‐4‐fluorophenol), were synthesized by reaction of VCl₃(THF)₃ with phenoxy–imine–thiophene proligands ( 1a – g ). All vanadium(III) complexes were characterized using elemental analysis and infrared and electron paramagnetic resonance spectroscopies. Upon activation with methylaluminoxane (MAO), vanadium precatalysts 2a – g proved active in the polymerization of ethylene (213.6–887.2 kg polyethylene (mol[V])⁻¹⋅h⁻¹), yielding high‐density polyethylenes with melting temperatures in the range 133–136 °C and crystallinities varying from 28 to 41%. The 2e/ MAO catalyst system was able to copolymerize ethylene with 1‐hexene affording poly(ethylene‐co ‐1‐hexene)s with melting temperatures varying from 126 to 102 °C and co‐monomer incorporation in the range 3.60–4.00%.     

A photochemical route to ferrocenyl‐substituted ferrapyrrolinone complexes

In the presence of iron pentacarbonyl, photochemical reaction between phenylisocyanate and ferrocenylacetylene results in ferrapyrrolinone complex [Fe₂(CO)₆(μ₂‐η³‐FcC═C(H)C(O)NPh)] ( 1 ) and maleimide 3‐ferrocenyl‐1‐phenyl‐1H ‐pyrrole‐2,5‐dione ( 2 ). Under similar experimental conditions, ferrocenyl−/phenyl‐substituted butadiyne primarily shows the activation of only one C☰C bond and results in ferrapyrrolinone complexes [Fe₂(CO)₆(μ₂‐η³‐FcC═C(C☰CR)C(O)NPh)] ( 3 , R = Fc; 3a , R = Ph), maleimides 3‐ferrocenyl‐1‐phenyl‐4‐(ferrocenylethynyl)‐1H –pyrrole‐2,5‐dione ( 5 ) and 3‐ferrocenyl‐1‐phenyl‐4‐(phenylethynyl)‐1H –pyrrole‐2,5‐dione ( 5a ) and [Fe₂(CO)₆(μ₂‐η³‐FcC═C(R)C(O)NPh)] ( 4 ; R  = 3‐ferrocenyl‐1‐phenyl‐1H ‐pyrrole‐2,5‐dione). Compound 4 consists of ferrapyrrolinone and a maleimide unit, formed by the activation of both C☰C bonds of diferrocenylbutadiyne. Activation of both C☰C bonds in a substituted butadiyne is a rare observation. Formation of the ferrapyrrolinone compounds is an advance over the earlier reported methods which generally use internal alkynes and involve prior synthesis of other clusters.     

NMR,IR and DFT studies of phenylplatinum complexes with O-monodentate coordinated silsesquioxanate and auxiliary phosphine ligands

The molecular structure and spectroscopic properties of a series of phenylplatinum complexes containing silsesquioxanate and phosphine ligands with general formula trans-[Pt{O₁₀Si₇(R)₇(OH)₂}(Ph)(L)₂] (1: R = cyclo-C₅H₉, L = PEt₃; 2: R = iso-C₄H₉, L = PEt₃; 3: R = CH₃, L = PEt₃; 4: R = cyclo-C₅H₉, L = PMe₃; 5: R = cyclo-C₅H₉, L = PMe₂Ph; 6: R = cyclo-C₅H₉, L = PPh₂Me; 7: R = cyclo-C₅H₉, L = PPh₃) have been investigated by DFT/OPW91/6-31G(d) calculations, ¹H, ¹³C, ²⁹Si and ³¹P NMR and IR spectroscopy. DFT molecular modeling based on available X-ray and NMR data for complexes 1 and 2 allowed deriving structure-NMR spectra correlations. It was found that the alkyl substituents (R) attached to Si atoms, cyclo-C₅H₉, iso-C₄H₉ and CH₃, slightly influence the geometry and multinuclear NMR parameters of the complexes in the series studied. The molecular structures of the Pt(II) complexes with R = cyclo-C₅H₉ (4–7) were predicted by DFT calculations of their simplified models with R = CH₃ (4′?7′). The geometry optimizations of 4′?7′ showed square-planar configuration of Pt(II) center bonded to two trans phosphine ligands, a phenyl group and an O-monocoordinated silsesquioxanate. The structures 4′?6′ are stabilized by two intramolecular hydrogen bonds similar to 1 and 2. A fast conformer exchange process A?B and switching of H-bonds in solution of 1–6 were suggested based on (i) the calculated conformer energies and small barrier of the process, and (ii) the observed single ¹H NMR signal at low magnetic field. The stability of the Pt(II) complexes depends on the nature of the phosphine ligands and decreases in the order PMe₂Ph > PMe₃ > PPh₂Me > PEt₃ > PPh₃. The PPh₃ ligands attached to Pt(II) in 7 cause the largest geometry changes and a new set of weaker hydrogen bonds. The comparison of the calculated NMR and IR parameters with the experimental spectroscopic data reveals good coincidence and thus confirmed the suggested molecular structures.     

Synthesis and structure of para‐toluene sulfonamide lanthanide complexes and their application in the polymerization of ε‐caprolactone

A series of para‐toluene sulfonamide ligands [TsNHPr‐i( HL ₁ ), TsNHBu‐t( HL ₂ ), TsNHPh( HL ₃ ), TsNHPhMe‐p( HL ₄ ), TsNHPhOMe‐p( HL ₅ )] were synthesized by amidation using para‐toluene sulfonyl chloride reacting with different primary amines. A series of homoleptic lanthanide complexes (Ln L₃, 1–10) (Ln = La, L = L₁ ( 1 ), Ln = Gd, L = L₂ ( 2 ), Ln = La, L = L₂ ( 3 ), Ln = Gd, L = L₂( 4 ), Ln = La, L = L₃ ( 5 ), Ln = Gd, L = L₃ ( 6 ), Ln = La, L = L₄ ( 7 ), Ln = Gd, L = L₄( 8 ), Ln = La, L = L₅ ( 9 ), Ln = Gd, L = L₅ ( 10 )) were prepared by amine elimination reactions of the ligands with Ln[N(SiMe₃)₂]₃ (Ln = La, Gd). Complexes 1 , 3 , 5 , 7 and 9 were all characterized by NMR spectra, and the structures of complex 3 was determined by single‐crystal X‐ray diffraction. Complex 3 crystallizes a binuclear cluster, consisting of two La³⁺ and six (TsNBu‐t)⁻ anions. Three (TsNBu‐t)⁻ anions are chelating to each La³⁺ as bidentate model with O and N forming three‐membered chelate rings; one of three anions is bridging to another La³⁺ via oxygen. All complexes were characterized using elemental analysis and infrared spectra. The catalytic properties of complexes 1–10 for the ring‐opening polymerization of ε‐caprolactone were studied and the results showed that all complexes are efficient initiators for this ring‐opening polymerization reaction.     

Synthesis of a series of new ruthenium organometallic complexes derived from pyridine‐imine ligands and their catalytic activity in oxidation of secondary alcohols

Reactions of pyridine imines [C₅H₄N‐2‐C(H) = N‐C₆H₄‐R] [R = H (1), CH₃ (2), OMe (3), CF₃ (4), Cl (5), Br (6)] with Ru₃(CO)₁₂ in refluxing toluene gave the corresponding dinuclear ruthenium carbonyl complexes of the type {μ‐η²‐CH[(2‐C₅H₄N)(N‐C₆H₄‐R)]}₂Ru₂(CO)₄(μ‐CO) [R = H (7); CH₃ (8); OMe (9); CF₃ (10); Cl (11); Br (12)]. All six novel complexes were separated by chromatography, and fully characterized by elemental analysis, IR, NMR spectroscopy. Molecular structures of 7, 10, 11, and 12 were determined by X‐ray crystal diffraction. Further, the catalytic performance of these complexes was also tested. The combination of {μ‐η²‐CH[(2‐C₅H₄N)(N‐C₆H₄‐R)]}₂Ru₂(CO)₄(μ‐CO) and NMO afforded an efficient catalytic system for the oxidation of a variety secondary alcohols.     

Synthesis and Anticancer Activity of Long-Chain Isonicotinic Ester Ligand-Containing Arene Ruthenium Complexes and Nanoparticles

Arene ruthenium complexes containing long-chain N-ligands L¹ = NC₅H₄–4-COO–C₆H₄–4-O–(CH₂)₉–CH₃ or L² = NC₅H₄–4-COO–(CH₂)₁₀–O–C₆H₄–4-COO–C₆H₄–4-C₆H₄–4-CN derived from isonicotinic acid, of the type [(arene)Ru(L)Cl₂] (arene = C₆H₆, L = L¹: 1; arene = p-MeC₆H₄Pr ⁱ , L = L¹: 2; arene = C₆Me₆, L = L¹: 3; arene = C₆H₆, L = L²: 4; arene = p-MeC₆H₄Pr ⁱ , L = L²: 5; arene = C₆Me₆, L = L²: 6) have been synthesized from the corresponding [(arene)RuCl₂]₂ precursor with the long-chain N-ligand L in dichloromethane. Ruthenium nanoparticles stabilized by L¹ have been prepared by the solvent-free reduction of 1 with hydrogen or by reducing [(arene)Ru(H₂O)₃]SO₄ in ethanol in the presence of L¹ with hydrogen. These complexes and nanoparticles show a high anticancer activity towards human ovarian cell lines, the highest cytotoxicity being obtained for complex 2 (IC₅₀ = 2 μM for A2780 and 7 μM for A2780cisR).     

Triphenylantimony(v) Derivatives of 2,2-Disubstituted Benzothiazoline Ligands: Synthetic and Spectroscopic Studies

The reactions of triphenylantimony(v) isopropoxide with 2,2-disubstituted benzothiazolines in a 1:2 molar ratio in refluxing benzene solution yielded the corresponding triphenylantimony(v) derivatives (1–5) of the type Ph₃Sb[SC₆H₄N: C(R)CH₂C(O)R']₂, [Where, R═CH₃, R'═CH₃(1); R═CH₃, R'═C₆H₅(2); R═CH₃, R'═4-CH₃C₆H₄(3); R═CH₃, R'═4-ClC₆H₄(4); and R═CF₃, R'═C₆H₅(5)]. All of these newly synthesized derivatives have been characterized by elemental analyses and molecular weight measurements as well as IR and NMR [¹H and ¹³C] spectral studies. On the basis of spectral data, seven-coordination around central antimony atom has been assigned to these derivatives.     

Palladium(II) compounds with planar chirality. X-Ray crystal structures of (+)-(R)-[{(η5-C5H4)–CHN–CH(Me)–C10H7}Fe(η5-C5H5)] and (+)-(Rp,R)-[Pd{[(Et–CC–Et)2(η5-C5H3)–CHN–CH(Me)–C10H7]Fe(η5-C5H5)}Cl]

A wide variety of planar chiral cyclopalladated compounds of general formulae [Pd{[(η⁵-C₅H₃)–CHN–CH(Me)–C₁₀H₇]Fe(η⁵-C₅H₅)}Cl(L)] (with L=py-d₅ or PPh₃), [Pd{[(η⁵-C₅H₃)–CHN–CH(Me)–C₁₀H₇]Fe(η⁵-C₅H₅)}(acac)] or [Pd{[(R¹–CC–R²)₂(η⁵-C₅H₃)–CHN–CH(Me)–C₁₀H₇]Fe(η⁵-C₅H₅)}Cl] (with R¹=R²=Et; R¹=Me, R²=Ph; R¹=H, R²=Ph; R¹=R²=Ph; R¹=R²=CO₂Me or R¹=CO₂Et, R²=Ph) are reported. The diastereomers {(R_p,R) and (S_p,R)} of these compounds have been isolated by either column chromatography or fractional crystallization. The free ligand (R)-(+)-[{(η⁵-C₅H₄)–CHN–CH(Me)–C₁₀H₇}Fe(η⁵–C₅H₅)] (1) and compound (+)-(R_p,R)-[Pd{[(Et–CC–Et)₂(η⁵-C₅H₃)–CHN–CH(Me)–C₁₀H₇]Fe(η⁵-C₅H₅)}Cl] (7a) have also been characterized by X-ray diffraction. Electrochemical studies based on cyclic voltammetries of all the compounds are also reported.     

Synthesis of aryl-functionalized, 1,5-disubstituted 1,2,3-triazoles and derivatives by arylation of zwitterionic ruthenium triazolato complexes

The synthesis of a series of ruthenium 1,5-disubstituted 1,2,3-triazolato complexes, 1,5-disubstituted 1,2,3-triazoles, and a triazolium salt is reported. Treatment of the ruthenium azido complex [Ru]-N₃ ( 1 , [Ru] = (η⁵-C₅H₅)(dppe)Ru, dppe = Ph₂PCH₂CH₂PPh₂) with an excess of ethyl propiolate results in the formation of a mixture of the Z- and E-forms of zwitterionic N(1)-bound N(3)-ethyl acryl-4-carboxylate triazolato complexes [Ru]N₃(CH=CHCO₂Et)C₂H(CO₂) ( Z - 2 ) and ( E - 2 ). The arylation of 2 with aromatic bromides gives a series of cationic N(1)-bound N(3)-ethyl acryl-4-alkoxycarbonyl triazolato complexes {[Ru]N₃(CH=CHCO₂Et)C₂H(CO₂CH₂R)}[Br] ( 3a , R = Ph ; 3b , R = C₆F₅; 3c , R = 4-C₆H₄CN, 3d , R = 2,6-C₆H₃F₂) and the subsequent cleavage of the Ru-N bond of 3a–d gives 1,5-disubstituted 1,2,3-triazoles N₃(CH=CHCO₂Et)C₂H(CO₂CH₂R) ( 4a , R = Ph; 4b , R = C₆F₅; 4c , R = 4-C₆H₄CN; 4d , R = 2,6-C₆H₃F₂) and [Ru]-Br. A 1,2,3-triazolium salt [N₃(CH=CHCO₂Et)(CH₂C₆F₅)C₂H₂][Br] ( 5 ) was formed by transformation of 4b in BrCH₂C₆F₅/chloroform mixture. The structures of Z-3a and Z-5 were confirmed by single-crystal x-ray diffraction analysis and both complexes participate in non-covalent aromatic interactions in the solid-state structures which can be favorable in the binding of DNA/biomolecular targets and have shown great potential in the application of biologically active anticancer drugs.     

A new family of octanuclear Mn complexes with a rod-like topology

Three new octanuclear compounds were prepared from reactions of [Mn(O₂CR)₂]·2H₂O (R = Et or Ph) with the diols 1,3-propanediol (pdH₂) or 2-methyl-1,3-propanediol (mpdH₂) in the presence of NaN₃. All three compounds [Mn₈(N₃)₄(O₂CR)₆(L)₄(py)₆] (L = pd²⁻, R = Et 1; L = mpd²⁻, R = Et 2; L = pd²⁻, R = Ph 3) (py = pyridine) possess a novel near-planar, rod-like topology. Dc and ac magnetic susceptibility studies in the 2–300 K range for complexes 1 and 2 revealed the presence of dominant antiferromagnetic exchange interactions, leading to diamagnetic ground spin states.     

Synthesis and reactivity of metal-containing monomers

Optically active mixed alkoxy orthotitanates with general formula Ti(OR¹)₂(OR²)(OR³) (R¹=Et, Buⁿ; R²=CH₂CH₂OCOC(Me)=CH₂; R³=menthyl, CH(Me)CH₂Me, CH(Ph)CH(NHMe)Me, CH(C₉H₆N)(C₉H₁₄N)) were obtained for the first time by transesterification. The Ti^IV monomers synthesized were characterized by elemental analysis, ozonolysis, and¹H and¹³C NMR and IR spectroscopy. Polymer products with optical activity were obtained by liquid phase radical copolymerization of Ti^IV-containing monomers. For Part 51, see Ref. 1. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1739–1743, September, 1999.     

Modified cyclopentadienyl molybdenum compounds with enhanced cytotoxic activity towards MOLT‐4 leukaemia cells

A series of new cyclopentadienyl molybdenum compounds bearing substituted phenanthroline ligands [(η⁵‐C₅H₄CH₂C₆H₄X‐4)Mo(CO)₂(^N,NL)][BF₄] (X = F, Cl, Br; ^N,NL = phen, 5‐NH₂‐phen, 4,7‐Ph₂‐phen) was prepared and characterized using infrared and NMR spectroscopies. Crystal structures of [(η⁵‐C₅H₄CH₂C₆H₄F‐4)Mo(CO)₂(NCMe)₂][BF₄], [(η⁵‐C₅H₄CH₂C₆H₄X‐4)Mo(CO)₂(phen)][BF₄] (X = F, Cl, Br) and [(η⁵‐C₅H₄CH₂C₆H₄Cl‐4)Mo(CO)₂(4,7‐Ph₂‐phen)][BF₄]⋅(4,7‐Ph₂‐phen)⋅HBF₄ were determined using X‐ray diffraction analysis. Biological studies revealed a strong cytotoxic effect of the chelating ligands. Although the cytostatic effect of the halogen in the side chain of the cyclopentadienyl ring is negligible, it could be used for future post‐modification of these types of cytotoxic active molybdenum‐based compounds.     

Photochemical reactions of M(CO)5THF (M = Cr, Mo, W) with thio Schiff bases

The hitherto unknown complexes, [M₂(CO)₆(μ-CO)(μ-L)], [M = Cr; 1, Mo; 2, W; 3] and [M₂(CO)₆(μ-CO)(μ-L′)], [M = Cr; 4, Mo; 5, W; 6] have been synthesized by the photochemical reactions of photogenerated intermediate, M(CO)₅THF (M = Cr, Mo, W) with thio Schiff base ligands, N,N′-bis(2-aminothiophenol)-1,4-bis(2-carboxaldehydephenoxy)butane (H ₂ L) and N,N′-bis(2-aminothiophenol)-1,7-bis(2-formylphenyl)-1,4,7-trioxaheptane (H ₂ L′). The complexes have been characterized by elemental analysis, LC-mass spectrometry, magnetic studies, FT-IR and ¹H NMR spectroscopy. The spectroscopic studies show that H ₂ L and H ₂ L′ ligands are converted to benzothiazole derivatives, L and L′ after UV irradiation and coordinated to the central metal as bridging ligands via the central azomethine nitrogen and sulphur atoms in 1–6.     

Synthesis and Characterization of Metal Complexes (M = Al,Ti, W,Zn) Containing Pyrrole‐imine Ligands

A series of metal compounds (M = Al, Ti, W, and Zn) containing pyrrole‐imine ligands have been prepared and structurally characterized. The reactions of AlMe₃ with one and three equivs of pyrrole‐imine ligand [C₄H₃NH‐(2‐CH=N? CH₂Ph)] ( 1 ) generated aluminum compounds Al[C₄H₃N‐(2‐CH=N? CH₂Ph)]Me₂ ( 2 ) and Al[C₄H₃N‐(2‐CH=NCH₂Ph)]₃ ( 3 ), respectively, in relatively high yield. Reacting two equivs of 1 with Ti(OⁱPr)₄, W(NH^tBu)₂(=N^tBu)₂, or ZnMe₂ afforded Ti[C₄H₃N‐(2‐CH=NCH₂Ph)]₂(OⁱPr)₂ ( 4 ), W[C₄H₃N‐(2‐CH=NCH₂Ph)]₂(=N^tBu)₂ ( 5 ), and Zn[C₄H₃N‐(2‐CH=NCH₂Ph)]₂ ( 6 ), respectively. All the compounds have been characterized by ¹H and ¹³C NMR spectroscopy. Compounds 3 – 6 have also been characterized by single‐crystal X‐ray structural analysis. The biting angles of pyrrole‐imine ligand with metals decrease and their related M? N_pyrrole and M? N_imine bond lengths increase in the order of 6 , 3 , 4 , and 5 .     

Synthesis, characterization, and spectroscopic studies of palladium(II) and silver(I) complexes of 4-methoxybenzoylmethylenetriphenylphosphorane and 4-fluorobenzoylmethylenetriphenylphosphorane

The reactions of 4-methoxybenzoylmethylenetriphenylphosphorane ylide (MOBPPY), {(Ph)₃PCHCOC₆H₄OMe}, and 4-flourobenzoylmethylenetriphenylphosphorane ylide (FBPPY) with [Pd(C₆H₄CH₂NH₂-κ²-C-N)ClL] (L = Py, 3-MePy, 4-MePy, or PPh₃), in equimolar ratios in CH₂Cl₂ yield [Pd(C₆H₄CH₂NH₂-κ²-C-N)L (Ye)]TfO [(L = PPh₃, Ye = MOBPPY; L = PPh₃, Ye = FBPPY; L = Py, Ye = MOBPPY; or L = 3-MePy, Ye = MOBPPY]. The reaction of MOBPPY with AgOTf (OTf = CF₃SO₃) in molar ratios (2:1) using dry acetone as solvent gives [Ag(MOBPPY)₂]OTf.     

Coordination and Activation of AlH and GaH Bonds

The modes of interaction of donor‐stabilized Group 13 hydrides (E=Al, Ga) were investigated towards 14‐ and 16‐electron transition‐metal fragments. More electron‐rich N‐heterocyclic carbene‐stabilized alanes/gallanes of the type NHC?EH₃ (E=Al or Ga) exclusively generate κ² complexes of the type [M(CO)₄(κ²‐H₃E?NHC)] with [M(CO)₄(COD)] (M=Cr, Mo), including the first κ² σ‐gallane complexes. β‐Diketiminato (′nacnac′)‐stabilized systems, {HC(MeCNDipp)₂}EH₂, show more diverse reactivity towards Group 6 carbonyl reagents. For {HC(MeCNDipp)₂}AlH₂, both κ¹ and κ² complexes were isolated, while [Cr(CO)₄(κ²‐H₂Ga{(NDippCMe)₂CH})] is the only simple κ² adduct of the nacnac‐stabilized gallane which can be trapped, albeit as a co‐crystallite with the (dehydrogenated) gallylene system [Cr(CO)₅(Ga{(NDippCMe)₂CH})]. Reaction of [Co₂(CO)₈] with {HC(MeCDippN)₂}AlH₂ generates [(OC)₃Co(μ‐H)₂Al{(NdippCme)₂CH}][Co(CO)₄] ( 12 ), which while retaining direct Al?H interactions, features a hitherto unprecedented degree of bond activation in a σ‐alane complex.     

Synthesis,characterization, and electrochemistry of monophosphine‐containing diiron propane‐1,2‐dithiolate complexes related to the active site of [FeFe]‐hydrogenases

Five monophosphine‐substituted diiron propane‐1,2‐dithiolate complexes as the active site models of [FeFe]‐hydrogenases have been synthesized and characterized. Reactions of complex [Fe₂(CO)₆{μ‐SCH₂CH(CH₃)S}] ( 1 ) with a monophosphine ligand tris(4‐methylphenyl)phosphine, diphenyl‐2‐pyridylphosphine, tris(4‐chlorophenyl)phosphine, triphenylphosphine, or tris(4‐fluorophenyl)phosphine in the presence of the oxidative agent Me₃NO·2H₂O gave the monophosphine‐substituted diiron complexes [Fe₂(CO)₅(L){μ‐SCH₂CH(CH₃)S}] [L = P(4‐C₆H₄CH₃)₃, 2 ; Ph₂P(2‐C₅H₄N), 3 ; P(4‐C₆H₄Cl)₃, 4 ; PPh₃, 5 ; P(4‐C₆H₄F)₃, 6 ] in 81%–94% yields. Complexes 2 – 6 have been characterized by elemental analysis, spectroscopy, and X‐ray crystallography. In addition, electrochemical studies revealed that these complexes can catalyze the reduction of protons to H₂ in the presence of HOAc.     

Double stereoselective coordination of chiral N,S ligands: Synthesis,coordination chemistry and utilization in Pd‐catalyzed allylic alkylation

A series of chiral pentane‐2,4‐diyl‐based thioether‐amine ligands [ 4 and 5 ; (R,S)‐ and (S,S)‐R¹SCH(CH₃)CH₂CH(CH₃)NHR², respectively, where 4a R¹ = iPr, R² = Ph; 4b R¹ = tBu, R² = Ph; 4c R¹ = 1‐Ad, R² = Ph; 5a R¹ = iPr, R² = Ph; 5b R¹ = tBu, R² = Ph; 5c R¹ = 1‐Ad, R² = Ph; 5d R¹ = iPr, R² = 4‐MeOC₆H₄; 5e R¹ = iPr, R² = 4‐MeC₆H₄; 5f R¹ = iPr, R² = 3,5‐Me₂C₆H₃] with stereogenic S‐ and N‐donor atoms has been prepared starting from cyclic sulfates via optically pure γ‐aminoalcohol or 2,4‐dimethylazetidine intermediates. The synthesis of the novel diastereomerically related ligand sets 4 and 5 was accomplished starting from the same source of chirality. The modular ligand structure and the novel synthetic strategies developed for their synthesis allowed the easy modification of the ligands’ (i) S‐ and (ii) N‐substituents, as well as (iii) the relative stereochemistry within the ligand backbone. Six‐membered [Pd(N,S)Cl₂]‐type chelate complexes of the diastereomerically related ligands 4a and 5a were synthesized and characterized by X‐ray crystallography in the solid phase, by density functional theory calculations and in solution by NMR spectroscopy. The coordination of 5a resulted in the formation of a single chair conformation by the stereospecific locking of both stereolabile (N and S) donor atoms. In contrast, compound 4a forms rapidly equilibrating palladium species due to the fast inversion of the sulfur donor. Ligands with stereochemically fixed donor atoms provided robust and efficient catalytic systems that can be effectively applied in alkylene carbonates as green reaction media. Remarkably, the phosphine‐free catalysts are air‐stable, and at room temperature in the presence of moisture gave excellent ee’s (up to 93%) in asymmetric allylation processes thanks to the double stereoselective coordination.     

Hexanuclear 3d − 4f metal–organic cages assembled from a carboxylic acid‐functionalized tris‐triazamacrocycle for highly selective fluorescent sensing of picric acid

Two Ln^III ions are sandwiched by dinuclear Co^II building blocks derived from a tris‐triazamacrocyclic ligand bearing pendant carboxylic acid functionality, 1,3,5‐tris((4,7‐bis(2‐carboxyethyl)‐1,4,7‐triazacyclonon‐1‐yl)methyl)‐benzene (H₆L), giving rising to two nanoscale heterometallic metal–organic cages formulated as [Co₄Ln₂(LH_2.5)₂(H₂O)₄]·(ClO₄)₆·NO₃·nH₂O [Ln = Dy, n = 12 ( 1 ); Ln = Yb, n = 9 ( 2 )], whose internal cavity accommodates a guest NO₃^? anion. Their hexanuclear cage‐like architectures are maintained both in solution and solid states as confirmed by mass spectrum as well as X‐ray diffraction experiments. These two cages display ligand‐based fluorescence emissions and therefore both were chosen to be operated as fluorescent chemosensors for the detection of nitroaromatic compounds. Attractively, these metal–organic cages allow highly selective and sensitive detection of picric acid (PA) over other nitroaromatics in solution and suspension, and the fluorescence resonance energy transfer (FRET) between the cage probes and PA is mainly responsible for the remarkable detection efficiency.     

Diversification of ortho‐Fused Cycloocta‐2,5‐dien‐1‐one Cores and Eight‐ to Six‐Ring Conversion by σ Bond C−C Cleavage

Sequential treatment of 2‐C₆H₄Br(CHO) with LiC≡CR¹ (R¹=SiMe₃, tBu), nBuLi, CuBr?SMe₂ and HC≡CCHClR² [R²=Ph, 4‐CF₃Ph, 3‐CNPh, 4‐(MeO₂C)Ph] at ?50 °C leads to formation of an intermediate carbanion (Z)‐1,2‐C₆H₄{C_A(=O)C≡C_BR¹}{CH=CH(CH^?)R²} ( 4 ). Low temperatures (?50 °C) favour attack at C_B leading to kinetic formation of 6,8‐bicycles containing non‐classical C‐carbanion enolates ( 5 ). Higher temperatures (?10 °C to ambient) and electron‐deficient R² favour retro σ‐bond C?C cleavage regenerating 4 , which subsequently closes on C_A providing 6,6‐bicyclic alkoxides ( 6 ). Computational modelling (CBS‐QB3) indicated that both pathways are viable and of similar energies. Reaction of 6 with H⁺ gave 1,2‐dihydronaphthalen‐1‐ols, or under dehydrating conditions, 2‐aryl‐1‐alkynylnaphthlenes. Enolates 5 react in situ with: H₂O, D₂O, I₂, allylbromide, S₂Me₂, CO₂ and lead to the expected C ‐E derivatives (E=H, D, I, allyl, SMe, CO₂H) in 49–64 % yield directly from intermediate 5 . The parents (E=H; R¹=SiMe₃, tBu; R²=Ph) are versatile starting materials for NaBH₄ and Grignard C=O additions, desilylation (when R¹=SiMe) and oxime formation. The latter allows formation of 6,9‐bicyclics via Beckmann rearrangement. The 6,8‐ring iodides are suitable Suzuki precursors for Pd‐catalysed C?C coupling (81–87 %), whereas the carboxylic acids readily form amides under T3P® conditions (71–95 %).