Synthesis of platinum-iodo-alkyl/aryl complexes in ligand-exchange reactions: Determination of the structure of Pt{(S,S)-bdpp}(X)I complexes (X = Me, I) by X-ray crystallography

Pt{(S,S)-bdpp}(R)I (bdpp = 2,4-bis(diphenylphosphino)pentane; R = Me, Ph, Bz, 2-Tioph) complexes were formed in alkyl/aryl ligand - iodide ligand-exchange reactions by reacting the corresponding Pt{(S,S)-bdpp}R₂ complexes with methyl iodide. The Pt{(S,S)-bdpp}(Me)I complex was isolated and fully characterised. The influence of the X ligand on the platinum-bdpp chelate conformation was investigated in Pt{(S,S)-bdpp}(X)I (X = I, SnCl₃, Me) complex series by means of X-ray crystallography.     

Syntheses and reactivities of azido coordinated CpCo(dithiolene) complexes

Azido coordinated dithiolene complexes [CpCo(N₃){S₂C₂(CO₂Me)₂}(S-CHR¹R²)], where R¹, R² = H (4a); R¹ = H, R² = SiMe₃ (4b); R¹ = H, R² = CO₂Et (4c), were synthesized by the reactions of the corresponding Cl⁻ coordinated precursors [CpCo(Cl){S₂C₂(CO₂Me)₂}(S-CHR¹R²)] (3a-3c) with sodium azide. The Cl⁻ coordinated complex 3d (R¹, R² = CO₂Me) did not produce any N₃⁻ coordinated complexes but formed the CR¹R²-bridged alkylidene adduct [CpCo{S₂C₂(CO₂Me)₂}(CR¹R²)] (2d; R¹, R² = CO₂Me). The structure of 4a was determined by X-ray diffraction study. In the molecular structure of 4a, the coordinated N₃⁻ ligand and CHR¹R² group were located at the same side with respect to the dithiolene ring (syn form), although the corresponding Cl⁻ precursor (3a; R¹, R² = H) was anti form. A structural conversion of syn/anti was conceivable during the Cl⁻/N₃⁻ ligand exchange. Thermal (80 °C) and photochemical reactions (Hg lamp) of 4a-4c were performed. Among them, 4c was relatively well reacted compared with the others to form the CR¹R²-bridged alkylidene adduct (2c; R¹ = H, R² = CO₂Et), followed by a formal HN₃ elimination, and the reaction also produced non-adduct of the cobalt dithiolene complex [CpCo{S₂C₂(CO₂Me)₂}] (1). The electrochemical 1e⁻ reduction of 4c underwent a formal N₃⁻ ligand elimination, and successive second reduction caused the CHR¹R² group elimination or reformed the CR¹R²-bridged alkylidene adduct 2c.     

Titanium (IV) complexes based on substituted 2-[(2-hydroxyethyl)]aminophenols

Novel substituted 2-[(2-hydroxyethyl)]aminophenols, MeN(CHR¹CR²R³OH)(C₆H₄-o-OH) (2-5), were synthesized by the reaction of 2-methylaminophenol with corresponding oxiranes. Titano-spiro-bis(ocanes) [MeN(CHR¹CR²R³O)(C₆H₄-o-O)]₂Ti 6-9 (2, 6, R¹ = H, R² = R³ = Me; 3, 7, R¹ = R² = Ph (treo-), R³ = H; 4, 8, R¹ = Ph, R² = R³ = H; 5, 9, R¹ = R² = H, R³ = Ph) based on [ONO]-ligands have been synthesized. The obtained compounds were characterized by ¹H and ¹³C NMR spectroscopy and elemental analysis data. The complex [Ti(μ²-O){O-o-C₆H₄}{μ²-CMe₂CH₂}NMe]₆ (10) was obtained by controlled hydrolysis of 6. Molecular structure of 10 was determined by X-ray structure analysis.     

Insertion of alkynes into the heterocycle of (η-pentaalkyl-2,3-dihydro-1,3-diborolyl)(η-pentamethylcyclopentadienyl)ruthenium: Formation and characterization of 4-borataborepine ruthenium complexes

The violet ruthenium complex [(η⁵-C₅Me₅)Ru(η⁵-C₃B₂Me₄R¹)] (2a, R¹ = Me) reacts with terminal alkynes R²CCH to give yellow 4-borataborepine compounds [(η⁵-C₅Me₅)Ru{η⁷-(MeC)₃(R¹B)₂(R²C₂H)}] (4c, R¹ = Me, R² = Ph; 4d, R¹ = Me, R² = SiMe₃; 4e, R¹ = Me, R² = H). The insertion of alkynes into the folded C₃B₂ heterocycle of 2a causes some steric hindrance, which yields with elimination of the distant boranediyl group the corresponding boratabenzene complexes 5 as byproducts. The analogous reactions with internal alkynes R²CCR² proceed slowly and afford predominantly the boratabenzene complexes [(η⁵-C₅Me₅)Ru{η⁶-(MeC)₃(MeB)(R²C)₂}] (5f, R² = Et, 5g, R² = p-tolyl), respectively. In the latter case, three byproducts are formed: methylboronic acid and 1,2,3,4-tetra-p-tolyl-1,3-butadiene (9) due to hydrolysis of the postulated 2,3,4,5-tetra-p-tolyl-1-methylborole (10) and unexpectedly, the cationic triple-decker complex [{(η⁵-C₅Me₅)Ru}₂{μ,η⁷-(MeC)₃(MeB)₂(CH)₂}]Cl (11) having two separated CH groups. The new compounds were characterized by NMR, MS, and single-crystal X-ray studies of 4c, 5f, 9 and 11.     

Synthesis and structures of nickel(II) and copper(II) compounds of 5,5,7,13-tetramethyl-13-nitro-1,4,8,11-tetraazacyclotetradecane and the 13-ethyl-5,5,7-trimethyl-homologue

Reduction by NaBH₄ of the imine functions of (5,7,7,13-tetramethyl-13-nitro-1,4,8,11-tetraazacyclotetradec-4-ene)-nickel(II) and -copper(II), and of their 13-ethyl-5,7,7-trimethyl-homologues, yield the nitro-substituted cyclic tetraamine cations (5,5,7,13-tetramethyl-13-nitro-1,4,8,11-tetraazacyclotetradecane)-nickel(II) and -copper(II), [M(neh)]²⁺, and (13-ethyl-5,5,7-trimethyl-homologues, [M(nph)]²⁺, respectively. The nickel(II) cations form square–planar, singlet ground, state salts with poorly coordinating anions and octahedral, triplet ground state, compounds with additional ligands, trans-β-[Ni(neh)A₂], A⁻ = Cl⁻, NCS⁻ and trans-β-[Ni(neh)A₂](ClO₄)₂, X = NH₃, MeCN, all with nitrogen configuration III, 1R,4R,8S,11S = β. With oxalate the chain-polymeric compound catena-trans-β-[Ni(neh)(μ-C₂O₄)]_n · 3n(H₂O) is formed. Folded macrocycle compounds cis-α-[Ni(neh)(C₅H₇O₂)]ClO₄ and cis-α-[{Ni(neh)}₂(C₂O₄)](ClO₄)₂ are formed with the chelates acetylacetonate and oxalate, with configuration 1R,4R,8R,11R = α. These react with HClO₄ to form metastable α-[Ni(neh)](ClO₄)₂ with retention of configuration. The copper(II) cations form crimson salts with poorly coordinating anions and compounds of the type β-[Cu(neh)A]ClO₄ of varying shades of blue with coordinating anions. Structures of singlet ground state square–planar nickel(II) compounds β-[Ni(neh)](ClO₄)₂ · H₂O, β-[Ni(neh)](ClO₄)₂, β-[Ni(neh)]₂[ZnCl₃(OH₂)]₂[ZnCl₄] · H₂O and α-[Ni(neh)](ClO₄)₂, the triplet ground state chain-polymeric compound catena-trans-β-[Ni(neh)(μ-C₂O₄)]_n · 3n(H₂O) and of square–pyramidal β-[Cu(nph)Cl]ClO₄ are reported.     

Cyclometalated N,N-dimethylbenzylamine ruthenium(II) complexes [Ru(C6HRRR-o-CH2NMe2)(bpy)(RCN)2]PF6 for bioapplications: synthesis, characterization, crystal structures, redox properties, and reactivity toward PQQ-dependent glucose dehydrogenase

Cyclometalated derivatives of ring-substituted N,N-dimethylbenzylamines with controlled redox potentials as potent mediators of bioelectrochemical electron transport are reported. The cycloruthenation of R¹R²R³C₆H₂CH₂NMe₂ (R¹, R², R³ = H, Me, ^tBuO, MeO, NMe₂, F, CF₃, CN, NO₂) by [(η⁶-C₆H₆)RuCl(μ-Cl)]₂ in the presence of NaOH/KPF₆ in acetonitrile or pivalonitrile affords cyclometalated complexes [(η⁶-C₆H₆)Ru(C₆HR¹R²R³-o-CH₂NMe₂)(RCN)]PF₆ [R = Me (1) and R = CMe₃ (2)] in good yields. Reactions of complexes 1 and 2 with 2,2′-bipyridine (bpy) in acetonitrile or pivalonitrile result in dissociation of η⁶-bound benzene and the formation of [Ru(C₆HR¹R²R³-o-CH₂NMe₂)(bpy)(RCN)₂]PF₆ [R = Me (3) and R = CMe₃ (4)]. All new compounds have been fully characterized by mass spectrometry, ¹H/¹³C NMR, and IR spectroscopy. An X-ray crystal structural investigation of complex 1 (R¹/R²/R³ = H/H/H) and two complexes of type 3 (R¹/R²/R³ = MeO/H/H, MeO/MeO/H) has been performed. Acetonitrile ligands of 3 are mutually cis and the σ-bound carbon is trans to one of the bpy nitrogens. Measured by the cyclic voltammetry in MeOH as solvent, the redox potentials of complexes 3 for the Ru^II/III feature cover the range 320-720 mV (versus Ag/AgCl) and correlate linearly with the Hammett constants. Complexes 3 mediate efficiently the electron transport between the active site of PQQ-dependent glucose dehydrogenase (PQQ = pyrroloquinoline quinone) and a glassy carbon electrode. Determined by cyclic voltammetry the second order rate constant for the oxidation of the reduced (by d-glucose) enzyme active site by Ru^III derivative of 3 (R¹/R²/R³ = H) (generated electrochemically) is as high as 4.8 × 10⁷ M⁻¹ s⁻¹ at 25 °C and pH 7.     

Synthesis, structure, properties, volatility, and thermal stability of molybdenum(II) and tungsten(II) complexes containing allyl, carbonyl, and pyrazolate or amidinate ligands

Treatment of M(allyl)(Cl)(CO)₂(py)₂ (M = Mo, W) with 1 equiv. of potassium pyrazolates in tetrahydrofuran at −78 °C afforded M(allyl)(R₂pz)(CO)₂(py)_n (R₂pz = 3,5-disubstituted pyrazolate; n = 1, 2) in 68-81% yields. X-ray crystal structure analyses of Mo(allyl)((CF₃)₂pz)(CO)₂(py)₂ and W(allyl)(tBu₂pz)(CO)₂(py) revealed η¹- and η²-coordination of the (CF₃)₂pz and tBu₂pz ligands, respectively. Analogous treatment of Mo(allyl)(Cl)(CO)₂(NCCH₃)₂ with 1 equiv. of tBu₂pzK in tetrahydrofuran at −78 °C afforded [Mo(allyl)(tBu₂pz)(CO)₂]₂ in 79% yield. An X-ray crystal structure analysis of [Mo(allyl)(tBu₂pz)(CO)₂]₂ showed a dimeric structure bridged by two μ-η²:η¹-tBu₂pz ligands. Treatment of M(allyl)(Cl)(CO)₂(py)₂ with 1 equiv. of lithium 1,3-diisopropylacetamidinate or lithium 1,3-di-tert-butylacetamidinate in diethyl ether at −78 °C afforded M(allyl)(iPrNC(Me)NiPr)(CO)₂(py) and M(allyl)(tBuNC(Me)NtBu)(CO)₂(py), respectively, in 68-78% yields. The new complexes were characterized by spectral and analytical methods and by X-ray crystal structure determinations. M(allyl)(iPrNC(Me)NiPr)(CO)₂(py) adopt pseudo-octahedral geometry about the metal centers, with the 1,3-diisopropylacetamidate ligand nitrogen atoms spanning one axial site and one equatorial site of the octahedron. By contrast, M(allyl)(tBuNC(Me)NtBu)(CO)₂(py) adopt pseudo-octahedral structures in which the two 1,3-di-tert-butylacetamidinate ligand nitrogen atoms span two equatorial coordination sites. Sublimation of M(allyl)(tBuNC(Me)NtBu)-(CO)₂(py) at 105 °C/0.03 Torr afforded ?7% yields of M(allyl)(tBuNC(Me)NtBu)(CO)₂, along with sublimed M(allyl)(tBuNC(Me)NtBu)(CO)₂(py). W(allyl)(tBuNC(Me)NtBu)(CO)₂ exists in the solid state as a 16-electron complex with distorted square pyramidal geometry. Many of the new complexes undergo dynamic ligand site exchange in solution, and these processes were probed by variable temperature ¹H NMR spectroscopy. The volatilities and thermal stabilities were evaluated to determine the potential of the new complexes for use as precursors in thin film growth experiments.     

Organotin(IV) triazolates: Synthesis and their spectral characterization

Some organotin(IV) triazolates of general formula R_nSn(L)_4 − n (where R = Me, n-Bu and Ph for n = 2; R = Me, n-Pr and n-Bu for n = 3 and HL = 3-amino-5-mercapto-1,2,4-triazole) have been synthesized by the reaction of R₂SnCl₂/R₃SnCl with NaL in 1:2/1:1 molar ratio. Whereas, Oct₂SnL₂ has been synthesized azeotropically by the reaction of Oct₂SnO and HL in 1:2 molar ratio. As good single crystals were not obtained, a large number of experimental techniques, viz. UV/Vis, IR, far-IR, multinuclear (¹H, ¹³C and ¹¹⁹Sn) NMR and ¹¹⁹Sn Mössbauer spectroscopic studies, were used to accomplish a definitive characterization and determination of their most probable structures. In these compounds triazole acts as a monoanionic bidentate ligand, coordinating through S_exo and N(4). The IR and ¹¹⁹Sn Mössbauer spectroscopic studies allow us to deduce a highly distorted cis-trigonal-bipyramidal structure for R₃SnL and a distorted skew trapezoidal-bipyramidal structure for R₂SnL₂, in the solid state. However, ¹H, ¹³C and ¹¹⁹Sn NMR spectral studies revealed that weak bonding between tin and N(4) is further weakened in the solution leading to pseudo-tetrahedral/tetrahedral structure.     

Synthesis, characterization and antitumor activity of 1,2-disubstituted ferrocenes and cyclodextrin inclusion complexes

Seven different ferrocene derivatives have been tested in vitro against Ehrlich ascites tumor cells. Neither ferrocene nor the monosubstituted derivative N,N-dimethylaminomethylferrocene showed cytotoxic activity (IC₅₀ > 1000 μM for 3 h treatments). Better results were obtained with 1,2-disubstituted derivatives. The IC₅₀ values ranged from 376.6 μM for 1,2-diformylferrocene to 71.2 μM for racemic 2-(N,N-dimethylaminomethyl)ferrocenecarboxamide. The latter derivative was also encapsulated in native β-cyclodextrin (CD), heptakis-2,3,6-tri-O-methyl-β-CD (TRIMEB) and 2-hydroxypropyl-β-CD (HPβCD) to give 1:1 (host:guest) inclusion compounds. The existence of true inclusion complexes in the solid state was confirmed by a combination of powder X-ray diffraction, thermogravimetric analysis, FTIR and ¹³C CP MAS NMR spectroscopy. The IC₅₀ value for the β-CD inclusion compound was identical to that obtained for the nonincluded ferrocene derivative. By contrast, the inclusion compounds comprising TRIMEB and HPβCD yielded IC₅₀ values of 25.2 and 20.0 μM, respectively. No obvious relationship could be established between the redox behavior of the compounds determined by cyclic voltammetry and the biochemical data.     

Structural characterization of triorganotin(IV) complexes with sodium fusidate and DFT calculations

Three new complexes of the steroid sodium fusidate (sodium 2-[(1S,2S,5R,6S,7S,10S,11S,13S, 14Z,15R,17R)-13-(acetyloxy)-5,17-dihydroxy-2,6,10,11-tetramethyl tetracyclo[8.7.0.0^2,7.0^11,15] heptadecan-14-ylidene]-6-methylhept-5-enoate = (NaFusidate, NaFA)]), with triorganotin(IV) moieties have been prepared and investigated by conventional techniques as FTIR, Mössbauer, ESI-MS and NMR spectroscopy. The isolated compounds showed stoichiometries organotin(IV)/fusidate 1/1, R₃Sn(IV)FA (R = Me, FA1; Bu, FA2; Ph, FA3). The ligand coordination sites were determined by FTIR spectroscopic measurements. In the complexes, the carboxylate group of the fusidate ligand behaves as monodentate monoanionic donor, binding the Sn(IV) through one oxygen atom.On the basis of C-Sn-O_COO angles, calculated through the rationalization of the ¹¹⁹Sn Mössbauer parameter nuclear quadrupole splitting, it has been confirmed that, in all the solid state complexes, the Sn(IV) was tetracoordinated in a distorted tetrahedral structure.Further data from ¹¹⁹Sn CP-MAS spectra confirmed the distorted tetrahedral arrangement.In MeOH solution, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy showed monomeric complexes, where the carboxylate group mainly acts as monodentate ester-type ligand, and the occurrence of a coordinated solvent molecule to the tin center, as validated by non-relativistic NMR DFT study.     

Anomalous charge transport in CeB6

The comprehensive study of conductivity σ, Hall coefficient R_H and Seebeck coefficient S has been carried out on high-quality single crystals of CeB₆ in a wide range of temperatures 1.8-300 K. An anomalous behavior of all transport characteristics (σ, R_H, S) was found for the first time in the vicinity of T^*≈80 K. The strong decrease of conductivity σ as well as the unusual asymptotic behavior of Seebeck coefficient S(T)∼−ln T observed below T^* allowed us to conclude in favor of crossover between different regimes of charge transport in CeB₆. The pronounced change of Hall mobility μ_H, which diminishes from the maximum value of 20 cm²/(V s) at T^* to the values of ∼6 cm²/(V s) at T∼10 K, seems to be attributed to the strong enhancement of charge carriers scattering due to fast spin fluctuations on Ce-sites. The low-temperature anomalies of the charge transport characteristics are compared with the predictions of the Kondo-lattice model.     

Highly efficient substitution of allylic picolinates with copper reagents derived from aryl-, alkenyl-, furyl-, and thienyl-lithiums

Substitution of optically active allylic picolinate, cis R¹-CH(OC(O)(2-Py))CHCHR² (R¹=(CH₂)₂Ph, R²=CH₂OTBS), with phenylcopper reagents derived from salt free PhLi (2 equiv) and CuBr·Me₂S (2 and 1 equiv, respectively) was highly promoted by MgBr₂ (3 equiv), producing anti S_N2′ product regio- and stereoselectively. This reagent system was proven to be general with several picolinates (R¹, R²: Ph(CH₂)₂, PMBO(CH₂)₃, Me, TBSOCH₂, PMBOCH₂, c-Hex). Furthermore, aryl copper reagents prepared from ArLi, which was in turn prepared by Li-halogen exchange, was proven to be compatible with the substitution in the presence of larger quantity of MgBr₂ than that of LiX coproduced by the exchange. Substitution was not interfered with the steric hindrance on aryl coppers (Ar: 2-MeOC₆H₄, 2,6-(MOMO)₂-4-MeC₆H₂, 2,6-Me₂C₆H₃, etc.). Similarly, stereodefined cis and trans alkenyl, furyl, and thienyl reagents gave the corresponding anti S_N2′ products efficiently.     

Fe Spin crossover materials based on dissymmetrical N4 Schiff bases including 2-pyridyl and 2R-imidazol-4-yl rings: Synthesis,crystal structure and magnetic and Mössbauer properties

The synthesis and characterization of new symmetrical Fe^II complexes, [FeL^A(NCS)₂] (1), and [FeL^Bx(NCS)₂] (2–4), are reported (L^A is the tetradentate Schiff base N,N′-bis(1-pyridin-2-ylethylidene)-2,2-dimethylpropane-1,3-diamine, and L^Bx stands for the family of tetradentate Schiff bases N,N′-bis[(2-R-1H-imidazol-4-yl)methylene]-2,2-dimethylpropane-1,3-diamine, with: R = H for L^B1 in 2, R = Me for L^B2 in 3, and R = Ph for L^B3 in 4). Single-crystal X-ray structures have been determined for 1 (low-spin state at 293 K), 2 (high-spin (HS) state at 200 K), and 3 (HS state at 180 K). These complexes remain in the same spin-state over the whole temperature range [80–400 K]. The dissymmetrical tetradentate Schiff base ligands L^Cx, N-[(2-R₂-1H-imidazol-4-yl)methylene]-N′-(1-pyridin-2-ylethylidene)-2,2-R₁-propane-1,3-diamine (R₁ = H, Me; R₂ = H, Me, Ph), containing both pyridine and imidazole rings were obtained as their [FeL^Cx(NCS)₂] complexes, 5–10, through reaction of the isolated aminal type ligands 2-methyl-2-pyridin-2-ylhexahydropyrimidine (R₁ = H, 5–7) or 2,5,5-trimethyl-2-pyridin-2-ylhexahydropyrimidine (R₁ = Me, 8–10) with imidazole-4-carboxaldehyde (R₂ = H: 5, 8), 2-methylimidazole-4-carboxaldehyde (R₂ = Me: 6, 9), and 2-phenyl-imidazole-4-carboxaldehyde (R₂ = Ph: 7, 10) in the presence of iron(II) thiocyanate. Together with the single-crystal X-ray structures of 7 and 9, variable-temperature magnetic susceptibility and Mössbauer studies of 5–10 showed that it is possible to tune the spin crossover properties in the [FeL^Cx(NCS)₂] series by changing the 2-imidazole and/or C2-propylene susbtituent of L^Cx.     

Structural, spectroscopic, and magnetic properties of a diphenolate-bridged FeNi complex showing excellent phosphodiester cleavage activity

To mimic the phosphate ester hydrolysis behavior of purple acid phosphatases the heterobimetallic complex [(BNPP)Fe^IIIL(μ-BNPP)Ni^II(H₂O)](ClO₄) (1) has been synthesized from the precursor complexes [Fe^III(LH₂)(H₂O)₂](ClO₄)₃·3H₂O and [Fe^III(LH₂)(H₂O)Cl](ClO₄)₂·2H₂O. In these compounds, L²⁻ is the anion of the tetraiminodiphenol macrocyclic ligand (H₂L), while LH₂ is the zwitterionic form in which the phenolic protons are shifted to the two metal-uncoordinated imine nitrogens, and BNPP is bis(4-nitrophenyl)phosphate. The X-ray crystal structure of compound 1 has been determined. The structure of 1 comprises of two edge-shared distorted octahedrons whose metal centers are bridged by two equatorial phenolate oxygens and two axially disposed oxygens of a BNPP ligand. The internuclear Fe?Ni distance is 3.083 Å. The high-spin iron(III) and nickel(II) in 1 are antiferromagnetically coupled (J = −7.1 cm⁻¹; H = −2JS₁·S₂) with S = 3/2 spin ground state. The phosphodiesterase activity of 1 has been studied in 70:30 H₂O-(CH₃)₂SO medium with NaBNPP as the substrate. The reaction rates have been measured by varying pH (3-10), temperature (25-50 °C), and with different concentrations of the substrate and complex at a fixed pH and temperature. Treatment of the rate data, obtained at pH 6.0 and at 35 °C, by the Michaelis-Menten approach have provided the following parameters: K_M = 3.6 × 10⁻⁴ M, V_max = 1.83 × 10⁻⁷ M s⁻¹, k_cat = 9.15 × 10⁻³ s⁻¹. As compared to the uncatalyzed hydrolysis rate of BNPP, the k_cat value is 8.3 × 10⁸ times higher, showing that 1 behaves as an excellent model for phosphate ester hydrolysis.     

Self-assembly of di- and triorganotin(IV) complexes: Syntheses, characterization and crystal structures of 1D polymeric chain containing O,O-diethyl or O,O-diisopropyl phosphoric acid ligands

A series of organotin(IV) complexes with O,O-diethyl phosphoric acid (L¹H) and O,O-diisopropyl phosphoric acid (L²H) of the types: [R₃Sn · L]_n (L = L¹, R = Ph 1, R = PhCH₂2, R = Me 3, R = Bu 4; L = L², R = Ph 9, R = PhCH₂10, R = Me 11, R = Bu 12), [R₂Cl Sn · L]_n (L = L¹, R = Me 5, R = Ph 6, R = PhCH₂7, R = Bu 8; L = L², R = Me 13, R = Ph 14, R = PhCH₂15, R = Bu 16), have been synthesized. All complexes were characterized by elemental analysis, TGA, IR and NMR (¹H, ¹³C, ³¹P and ¹¹⁹Sn) spectroscopy analysis. Among them, complexes 1, 2, 3, 5, 8, 9 and 11 have been characterized by X-ray crystallography diffraction analysis. In the crystalline state, the complexes adopt infinite 1D infinite chain structures which are generated by the bidentate bridging phosphonate ligands and the five-coordinated tin centers.     

Formation and crystal structures of [(alkoxy)bis(pyridin-2-yl)methanolato-N,O,N]tin(IV) complexes

Reactions of bis(pyridin-2-yl)ketone with tin tetrahalides, SnX₄ (X = Cl or Br), or organotin trichlorides, R^′SnCl₃ (R^′ = Ph, Bu or CH₂CH₂CO₂Me), in ROH (R = Me or Et) readily produces RObis(pyridin-2-yl)methanolato)tin complexes, [5: RO(py)₂C(OSnX₃)] (5: R,X = Me,Cl; Et,Cl; Et,Br) or [6: MeO(py)₂C(OSnCl₂R^′)] (R^′ = Ph, Bu, CH₂CH₂CO₂Me). In addition, halide exchange reaction between SnI₄ and (5: R,X = Me,Cl) occurred to give (5: R,X = Me,I). The crystal structures of six tin(IV) derivatives indicated, in all cases, a monoanionic tridentate ligand, [RO(py)₂C(O⁻)-N,O,N], arranged in a fac manner about a distorted octahedral tin atom. The Sn–O and Sn–N bonds lengths do not show much variation amongst the six complexes despite the differences in the other ligands at tin.     

Syntheses, structures, physical properties, and electronic structures of KLn2CuS4 (Ln=Y, Nd, Sm, Tb, Ho) and K2Ln4Cu4S9 (Ln=Dy, Ho)

Seven new quaternary metal sulfides, KY₂CuS₄, KNd₂CuS₄, KSm₂CuS₄, KTb₂CuS₄, KHo₂CuS₄, K₂Dy₄Cu₄S₉, and K₂Ho₄Cu₄S₉, were prepared by the reactive flux method. All crystallographic data were collected at 153 K. The isostructural compounds KLn₂CuS₄ (Ln=Y, Nd, Sm, Tb, Ho) crystallize in space group Cmcm of the orthorhombic system with four formula units in cells of dimensions (Ln, a, b, c (Å)): Y, 3.9475(9), 13.345(3), 13.668(3); Nd, 4.0577(3), 13.7442(10), 13.9265(10); Sm, 4.0218(4), 13.6074(14), 13.8264(14); Tb, 3.9679(5), 13.4243(17), 13.7102(18); Ho, 3.9378(3), 13.3330(11), 13.6487(11). The corresponding R₁ indices for the refined structures are 0.0197, 0.0153, 0.0158, 0.0181, and 0.0178. The isostructural compounds K₂Dy₄Cu₄S₉ and K₂Ho₄Cu₄S₉ crystallize in space group C2/m of the monoclinic system with two formula units in cells of dimensions (Ln, a, b, c (Å), β (°)): Dy, 13.7061(13), 3.9482(4), 15.8111(15), 109.723(1); Ho, 13.6760(14), 3.9360(4), 15.7950 (16), 109.666(2). The corresponding R₁ indices are 0.0312 and 0.0207. Both structure types are closely related three-dimensional tunnel structures. The tunnels are filled with bicapped trigonal-prismatically coordinated K atoms. Their anionic frameworks are built from LnS₆ octahedra and CuS₄ tetrahedra. KLn₂CuS₄ contains _∞¹[CuS₃⁵⁻] chains of vertex-sharing tetrahedra and K₂Ln₄Cu₄S₉ contains _∞¹[Cu₄S₈¹²⁻] chains of tetrahedra. K₂Ho₄Cu₄S₉ shows Curie-Weiss paramagnetic behavior between 5 and 300 K, and has an effective magnetic moment of 10.71 μ_B for Ho³⁺ at 293 K. Optical band gaps of 2.17 eV for KSm₂CuS₄ and 2.43 eV for K₂Ho₄Cu₄S₉ were deduced from diffuse reflectance spectra. A first-principles calculation of the density of states and the frequency-dependent optical conductivity was performed on KSm₂CuS₄. The calculated band gap of 2.1 eV is in good agreement with the experimental value.     

Syntheses,characterizations and crystal structures of monomeric or macrocyclic compounds of di- or triorganotin (IV) moieties with 4,4′-thiodibenzenethiol

Six organotin compounds with 4,4′-thiodibenzenethiol (LH₂) of the type R_nSnL_4−nSnR_n (n = 3: R = Me 1, Ph 2, PhCH₂3, n = 2: R = Me 4, Ph 5, PhCH₂6) have been synthesized. All compounds were characterized by elemental analysis, IR and NMR (¹H, ¹³C, and ¹¹⁹Sn) spectra. The structures of compounds 1, 2, 4, 5 and 6 were also determined by X-ray diffraction analysis, which revealed that compounds 1 and 2 were monomeric structures, compounds 4, 5 and 6 were centrosymmetric dinuclear macrocyclic structures, and all the tin(IV) atoms are four-coordinated. Furthermore, supramolecular structures were also found in compounds 1, 2, 4, 5 and 6, which exhibit one-dimensional chains, two-dimensional networks or three-dimensional structures through intermolecular C–H?S weak hydrogen bonds (WHBs), non-bonded Sn?S interactions or C–H?π interactions.     

The synthesis, structural characterization and in vitro anti-cancer activity of novel N-(3-ferrocenyl-2-naphthoyl) dipeptide ethyl esters and novel N-(6-ferrocenyl-2-naphthoyl) dipeptide ethyl esters

N-(3-ferrocenyl-2-naphthoyl) dipeptide esters (5-7) and N-(6-ferrocenyl-2-naphthoyl) dipeptide esters (8-10) were prepared by coupling either 3-ferrocenylnaphthalene-2-carboxylic acid 2 or 6-ferrocenylnaphthalene-2-carboxylic acid 4 to the dipeptide ethyl esters GlyAla(OEt) (5, 8), AlaGly(OEt) (6, 9), and AlaAla(OEt) (7, 10) using the standard N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC), 1-hydroxybenzotriazole (HOBt) protocol. All the compounds were fully characterized using a combination of ¹H NMR, ¹³C NMR, DEPT-135 and ¹H-¹³C COSY (HMQC) spectroscopy, electrospray ionization mass spectrometry (ESI-MS) and cyclic voltammetry (CV). In vitro, the cytotoxic effects of compounds 5-10 show improvements over the corresponding N-(ferrocenyl)benzoyl derivatives, with IC₅₀ values against the H1299 lung cancer cells ranging from 1.2 μM to 8.0 μM. N-(6-ferrocenyl-2-naphthoyl)-glycine-l-alanine ethyl ester 8 was found to be the most active derivative of the naphthoyl series so far, displaying an IC₅₀ value of 1.3 ± 0.1 μM. This value is slightly lower than that found for the clinically employed anti-cancer drug cisplatin (IC₅₀ = 1.5 ± 0.1 μM against H1299).     

Ring-opening polymerization of l-lactide by organotin(IV)alkoxides,R2Sn(OPr)2: Estimation of the activation parameters

The ring-opening polymerization of l-lactide, l-LA, to give poly-l-lactide by R₂Sn(OPrⁱ)₂ compounds, where R = Buⁿ and p-XC₆H₄ (X = CF₃, F, H, Me and OMe) has been studied in benzene over a temperature range. There is a relatively small variation in ΔH^≠ as a function of R with all the values falling within the range 11 ± 2 kcal mol⁻¹. The entropy of activation, ΔS^≠, is consistently large and negative, −50 ± 5 eu, supporting the view that the ring-opening event, the enchainment step involves a highly ordered transition state. The crystal and molecular structures of the compounds Ph₂Sn(OPrⁱ)₂, (p-FC₆H₄)₂Sn(OPrⁱ)₂ and (p-Me₂NC₆H₄)₃SnOPrⁱ are also reported. While the latter compound is monomeric in the solid state the former are both dimeric with a pair of bridging OPrⁱ ligands.