Silver(I) acetylides stabilized by η-alkynes: Synthesis, reaction chemistry and solid state structures

Individual synthetic routes to heterobimetallic Ti(IV)-Ag(I) acetylides of type {[Ti](μ-σ,π-CCR¹)₂}AgCCR² ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti: R¹ = SiMe₃: 6, R² = SiMe₃; 7, R² = Ph. R¹ = ^tBu: 8, R² = SiMe₃; 9, R² = Ph. [Ti] = (η⁵-C₅H₅)₂Ti): 10, R¹ = ^tBu, R² = SiMe₃) including (i) the reaction of {[Ti](μ-σ, π-CCR¹)₂}AgNO₃ ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti): 1, R¹ = SiMe₃; 2, R¹ = ^tBu. [Ti] = (η⁵-C₅H₅)₂Ti: 3, R¹ = ^tBu) with LiCCR² (4, R² = SiMe₃; 5, R² = Ph) and (ii) treatment of [Ti](CCSiMe₃)₂ ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti) (11) with [AgCCR²] (12, R² = SiMe₃; 13, R² = Ph) are described. The reactions of 1-3 with 4 or 5 appeared to be sensitive towards stoichiometry because an excess of 4 or 5 resulted in the formation of [(Ag(CCR²)₂)Li(OEt₂)]_n (14) and [Ti](CCR¹)₂. Coordination polymer 14 is also accessible, when, for example, [AgCCSiMe₃] (12) is treated with 1 eq. of LiCCSiMe₃ (4) in diethyl ether.The titanium(IV)-silver(I) acetylides 6-10 are stable in the dark and at low temperature, while on exposure to light and on heating they decompose to give R²CC-CCR² together with [Ti](CCR¹)₂ and elemental silver.Complexes 6-10 contain a mono-nuclear AgCCR² entity stabilized by the chelate-bonded organometallic π-tweezer molecule [Ti](CCSiMe₃)₂, which was evinced by structure determination of 7 in the solid state. In 14 linear [Me₃SiCC-Ag-CCSiMe₃]⁻ units are connected by [Li(OEt₂)]⁺ building blocks forming a coordination polymer.     

Synthesis, characterization and applications in ethylene polymerization of asymmetric ansa-titanocene complexes. Molecular structure of [Ti{Me2Si(η-C5Me4)(η-C5H3iPr)}Cl2]

The ansa-titanocene complexes, [Ti{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₃R)}Cl₂] (R = Me (5), iPr (6), tBu (7), SiMe₃ (8)), were obtained from the reaction of Li₂{Me₂Si(C₅Me₄)(C₅H₃R)} (R = Me (1), iPr (2), tBu (3), SiMe₃ (4)) with [TiCl₄(THF)₂], respectively. Compounds 5-8 have been tested as catalysts in the polymerization of ethylene and compared with the ansa-titanocene complexes [Ti{Me₂Si(η⁵-C₅H₄)₂}Cl₂] and [Ti{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂]. The resulting polyethylene showed molecular weights of about 200 000 g mol⁻¹ and polydispersity values of approximately 3. In addition, the molecular structure of 6 has been determined by single crystal X-ray diffraction studies.     

Monoterpenoids from the aerial parts of Aruncus dioicus var. kamtschaticus and their antioxidant and cytotoxic activities

The aerial parts of Aruncus dioicus var. kamtschaticus afforded five new monoterpenoids (1-5): 4-(erythro-6,7-dihydroxy-9-methylpent-8-enyl)furan-2(5H)-one (1, aruncin A), 2-(8-ethoxy-8-methylpropylidene)-5-hydroxy-3,6-dihydro-2H-pyran-4-carboxylic acid (2, aruncin B), 4-(hydroxymethyl)-6-(8-methylprop-7-enyl)-5,6-dihydro-2H-pyran-2-one-11-O-β-d-glucopyranoside (3, aruncide A), (3S,4S,5R,10R)-3-(10-ethoxy-11-hydroxyethyl)-4-(5-hydroxy-7-methylbut-6-enyl)oxetan-2-one-11-O-β-d-glucopyranoside (4, aruncide B), and (3S,4S,5R,7R)-5-(9-methylprop-8-enyl)-1,6-dioxabicyclo[3,2,0]heptan-2-one-7-(hydroxymethyl)-12-O-β-d-glucopyranoside (5, aruncide C). Compound 2 showed potent cytotoxicity against Jurkat T cells with an IC₅₀ value of 17.15 μg/mL. In addition, compounds 7 and 10 exhibited moderate antioxidant activity with IC₅₀ values of 46.3 and 11.7 μM, respectively.     

β-Diketiminato 3d-metal compounds: Synthesis, characterization and catalytic behavior towards ethylene

The lithium β-diketiminate (1c, [Li{N(2,6-ⁱPr₂C₆H₃)C(Ph)CHC(^tBu)NH}]₂ represented as (LiL)₂) reacted with 3d-metal (II) chlorides to afford the corresponding compounds (2-7). All metal compounds were fully characterized by elemental, spectroscopic analyses and the single-crystal X-ray diffraction. The coordination geometries around the metals are shown to be tetrahedral within the trinuclear Co₂Li compound (2), planar in ML₂ (M = Co, 3), pseudo-tetrahedral conformation in the ML₂ with M as Mn (4), Fe (5) or Zn (6), and square planar in the dinickel compound (7). Indicated by the trimetallic Co₂Li compound 2, a six-membered ring is constructed of three metal atoms and three bridged chlorides as a twisted conformation. An inversion center is present in the centroid of the Ni₂Cl₂ four-membered ring within compound 7. The plausible mechanism of forming ML₂ was proposed through the chloro-bridged multinuclear compounds on the basis of isolated intermediates of trinuclear (2) and dinuclearic (7) compounds. Upon treatment with methylaluminoxane (MAO), the nickel compound 7 possessed good activity towards ethylene oligomerization, whereas the other metal compounds showed moderate activities towards ethylene polymerization.     

Synthesis, characterizations, and crystal structures of triorganotin(IV) derivatives with areneseleninic acids

Six new triorganotin(IV) complexes, [R₃Sn(O₂SeC₆H₄Cl)]_n (R = Me 1; Ph 2), [R₃Sn(O₂SeC₆H₄Me)]_n (R = Me 3; Ph 4), [R₃Sn(O₂SeC₆H₄Bu)]_n (R = Me 5; Ph 6) have been synthesized by the reaction of 4-chlorobenzeneseleninic acid, p-Tolueneseleninic acid, and 4-tert-butylbenzeneseleninic acid with triorganotin(IV) chloride in the presence of sodium ethoxide. All of the complexes were characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, and ¹¹⁹Sn) spectroscopy, and X-ray crystallography. Crystal structures show that all of the complexes exhibit 1D infinite chain structures which are generated by the bidentate oxygen atoms and the five-coordinated tin centers.     

Cyclic and high molecular weight chiral binaphthoxy-phosphazene polymers carrying Br or trimethylsilyl-acetylene groups

The new chiral and functionalized cyclic binaphthoxyphosphazenes R,R,R-[N₃P₃(O₂C₂₀H₁₀Br₂)₃] (R-1), R,R,R-[N₃P₃(O₂C₂₀H₁₀(CCSiMe₃)₂)₃] (R-2), and the high molecular weight linear polymers R/S-[NP(O₂C₂₀H₁₀Br₂)]_n (R/S-3), R-[NP(O₂C₂₀H₁₀Br₂)]_n (R-3), and R-{NP[O₂C₂₀H₁₀(CCSiMe₃)₂]}_n, (R-4), with M_w on the order of 10⁶ and very high T_g, have been synthesized and characterized by IR and NMR spectroscopy. The optically active polymer (R-3) was configurationally stable below 300 °C, but at higher temperatures an atropisomerization process took place that became faster near the glass transition temperature (ca. 350 °C).     

Palladium(II) oxalato complexes involving N6-(benzyl)-9-isopropyladenine-based N-donor carrier ligands: Synthesis, general properties, H, C and N{H} NMR characterization and in vitro cytotoxicity

Reactions of potassium bis(oxalato)palladate dihydrate, K₂[Pd(ox)₂]·2H₂O, with two molar equivalents of N6-(benzyl)-9-isopropyladenine-based organic molecules (L_1-7), i.e. 2-chloro-N6-(2-methoxybenzyl)-9-isopropyladenine (L₁), 2-chloro-N6-(3-methoxybenzyl)-9-isopropyladenine (L₂), 2-chloro-N6-(3,5-dimethoxybenzyl)-9-isopropyladenine (L₃), 2-(1-ethyl-2-hydroxyethylamino)-N6-(benzyl)-9-isopropyladenine (L₄), 2-(1-ethyl-2-hydroxyethylamino)-N6-(2-methoxybenzyl)-9-isopropyladenine (L₅), 2-(1-ethyl-2-hydroxyethylamino)-N6-(3-methoxybenzyl)-9-isopropyladenine (L₆) and 2-(1-ethyl-2-hydroxyethylamino)-N6-(4-methoxybenzyl)-9-isopropyladenine (L₇), provided a series of seven palladium(II) oxalato (ox) complexes of the general formula [Pd(ox)(L_1-7)₂]·nH₂O (1-7; n = 0 for 4, 5 and 7, ¾ for 1 and 2, 1 for 6, and 3 for 3). The compounds were characterized by elemental analysis, IR, Raman, ¹H, ¹³C and ¹⁵N{¹H} NMR spectroscopy, ESI+ mass spectrometry, molar conductivity and TG/DTA thermal analysis. The geometry of [Pd(ox)(L₂)₂] (2) was optimized on the B3LYP/6-311G∗/LANL2DZ level of theory. The complexes 4-7 represent the first palladium(II) oxalato complexes with a PdN₂O₂ donor set, which involve highly potent purine-based cyclin-dependent kinase (CDK) inhibitors (L_4-7) as carrier N-donor ligands. The selected complexes 1, 3-5 and 7 were tested by an MTT assay for their in vitro cytotoxic activity against human osteosarcoma (HOS) cancer cell line. The highest activity was found for the complexes 5 (IC₅₀ = 34.9 μM) and 7 (IC₅₀ = 39.2 μM).     

Syntheses and characterization of titanium malonato and amino acid complexes: [Ti(cp)2(OOCCH2NMe2)] - The first structurally characterized α-amino acid titanium(III) complex

The reaction of [Ti(cp^∗)₂(BTMSA)] (1) (cp^∗ = η⁵-C₅Me₅, BTMSA = bis(trimethylsilyl)acetylene) with malonic acids ((HOOC)₂CR₂, R = H, Me) and N,N-dimethylglycine resulted in the formation of titanium(IV) dicarboxylato complexes [Ti(cp^∗)₂{(OOC)₂CR₂}] (R = H, 2; R = Me, 3) and an α-amino acid titanium(III) complex [Ti(cp^∗)₂(OOCCH₂NMe₂)] (4). The identities of complexes 2-4 were confirmed by microanalysis, ¹H and ¹³C NMR spectroscopy (2, 3), ESI-MS and CID experiments (2, 3) as well as by ESR and magnetic measurements (μ_eff = 1.81, 298 K) for 4. Single X-ray diffraction analyses of 2 and 4 exhibited monomolecular complexes in which the titanium atom is distorted tetrahedrally coordinated by two η⁵-C₅Me₅ rings and by the chelating bound malonato-κ²O,O′ (2) and N,N-dimethylglycinato-κ²O,O′ ligand (4).     

Molecular interactions of zinc(II) cyclams with polycarboxylato ligands

Four new zinc(II) cyclams of the composition {Zn(L)(tp²⁻) · H₂O}_n (1), {Zn(L)(H₂bta²⁻) · 2H₂O}_n (2), [Zn₂(L)₂(ox²⁻)] 2ClO₄ · 2DMF (3), and Zn(L)(H₂btc⁻)₂ · 2DMF (4), where L = cyclam, tp²⁻ = 1,4-benzenedicarboxylate ion, H₂bta²⁻ = 1,2,4,5-benzenetetracarboxylate ion, ox²⁻ = oxalate ion, DMF = N,N-dimethylformamide, and H₂btc⁻ = 1,3,5-benzenetricarboxylate ion, have been synthesized and structurally characterized by a combination of analytical, spectroscopic and crystallographic methods. The carboxylato ligands in the complexes 1-4 show strong coordination tendencies toward zinc(II) cyclams with hydrogen bonding interactions between the pre-organized N-H groups of the macrocycle and oxygen atoms of the carboxylato ligands. The macrocycles in 1, 2, and 4 adopt trans-III configurations with the appropriate R,R,S,S arrangement of the four chiral nitrogen centers, respectively. However, the complex 3 shows an unusual cis V conformation with the R,R,R,R nitrogen configuration. The finding of strong interactions between the carboxylato ligands and the zinc(II) ions may provide additional knowledge for the improved design of receptor-targeted zinc(II) cyclams in anti-HIV agents.     

Synthesis, characterization and in vitro cytotoxicity of the first palladium(II) oxalato complexes involving adenine-based ligands

The first [Pd(Lⁿ)₂(ox)] xH₂O oxalato(ox) complexes involving 2-chloro-N6-(benzyl)-9-isopropyladenine (L¹; complex 1), 2-chloro-N6-(4-methoxybenzyl)-9-isopropyladenine (L²; 2), 2-chloro-N6-(2,3-dimethoxybenzyl)-9-isopropyladenine (L³; 3), 2-chloro-N6-(2,4-dimethoxybenzyl)-9-isopropyladenine (L⁴; 4), and 2-chloro-N6-(4-methylbenzyl)-9-isopropyladenine (L⁵; 5) have been synthesized by the reactions of potassium bis(oxalato)palladate(II) dihydrate, [K₂Pd(ox)₂]·2H₂O, with the mentioned organic compounds (H₂ox = oxalic acid; x = 0 for 1-3 and 5 or 2 for 4). Elemental analyses (C, H, N), FTIR, Raman and NMR (¹H, ¹³C, ¹⁵N) spectroscopies, conductivity measurements and thermal studies (thermogravimetric and differential thermal analyses, TG/DTA) have been used to characterize the prepared complexes. The molecular structures of [Pd(L²)₂(ox)] (2) and [Pd(L⁵)₂(ox)]·L⁵·Me₂CO (5·L⁵·Me₂CO) have been determined by a single crystal X-ray analysis. The geometry of these complexes is slightly distorted square-planar with two appropriate Lⁿ (n = 2 or 5) molecules mutually arranged in the head-to-head (2) or head-to-tail (5) orientation. The Lⁿ ligands are coordinated to the central Pd(II) ion via the N7 atoms. The same conclusions regarding the binding properties of L¹-L⁵ ligands can be made based on multinuclear NMR spectra. In vitro cytotoxicity of the complexes 1-5 has been evaluated against human chronic myelogenous leukaemia (K562) and human breast adenocarcinoma (MCF7) cancer cell lines. Significant cytotoxicity has been determined for the complexes 3 (IC₅₀ = 6.2 μM) and 5 (IC₅₀ = 6.8 μM) on the MCF7 cell line, which is even better than that found for the well-known and widely-used platinum-bearing antineoplastic drugs, i.e. oxaliplatin and cisplatin.     

Syntheses and characterization of triorganotin(IV) complexes of Schiff base derive from 4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol and 5-amino-1,3,4-thiadiazole-2-thiol with p-phthalaldehyde

Eight triorganotin complexes of the types [(R₃Sn)₂(C₂₄H₁₆N₈S₂)].Y (R = Ph, Y = 0 (1); R = PhCH_2, Y = 2CH₃OH (2); R = n-Bu, Y = 0 (3)), [(R₃Sn)₂(C₂₄H₁₆N₈S₂)]_n (R = Me (4)), [(R₃Sn)₂(C₁₂H₆N₆S₄)] · Y (R = Ph, Y = CH₂Cl₂ (5); R = PhCH_2, Y = 0 (6)) and [(R₃Sn)₂(C₁₂H₆N₆S₄)] (R = Bu (7), R = Me (8)) have been obtained by H₂L₁ (H₂L₁ derived from 4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol) and H₂L₂ (H₂L₂ derived from 5-amino-1,3,4-thiadiazole-2-thiol) with triorganotin chloride in the presence of sodium ethoxide. All the complexes were characterized by elemental, IR and NMR spectra analyses, except for complexes 1, 3, 6 and 8, other complexes were also characterized by X-ray diffraction analyses, which reveal that complexes 2 and 5 are dinuclear structures, complex 4 has a 2D network structure and complex 7 forms a macrocyclic structure linked by intermolecular N → Sn interactions.     

Heteroligand copper(I) complexes of N-thiophosphorylated thioureas and phosphanes: Versatile structures and luminescence

Reaction of the potassium salts of (EtO)₂P(O)CH₂C₆H₄-4-(NHC(S)NHP(S)(OiPr)₂) (HL^I), (CH₂NHC(S)NHP(S)(OiPr)₂)₂ (H₂L^II) or cyclam(C(S)NHP(S)(OiPr)₂)₄ (H₄L^III) with [Cu(PPh₃)₃I] or a mixture of CuI and Ph₂P(CH₂)_1-3PPh₂ or Ph₂P(C₅H₄FeC₅H₄)PPh₂ in aqueous EtOH/CH₂Cl₂ leads to [Cu(PPh₃)L^I] (1), [Cu₂(Ph₂PCH₂PPh₂)₂L^II] (2), [Cu{Ph₂P(CH₂)₂PPh₂}L^I] (3), [Cu{Ph₂P(CH₂)₃PPh₂}L^I] (4), [Cu{Ph₂P(C₅H₄FeC₅H₄)PPh₂}L^I] (5), [Cu₂(PPh₃)₂L^II] (6), [Cu₂(Ph₂PCH₂PPh₂)L^II] (7), [Cu₂{Ph₂P(CH₂)₂PPh₂}₂L^II] (8), [Cu₂{Ph₂P(CH₂)₃PPh₂}₂L^II] (9), [Cu₂{Ph₂P(C₅H₄FeC₅H₄)PPh₂}₂L^II] (10), [Cu₈(Ph₂PCH₂PPh₂)₈L^IIII₄] (11), [Cu₄{Ph₂P(CH₂)₂PPh₂}₄L^III] (12), [Cu₄{Ph₂P(CH₂)₃PPh₂}₄L^III] (13) or [Cu₄{Ph₂P(C₅H₄FeC₅H₄)PPh₂}₄L^III] (14) complexes. The structures of these compounds were investigated by IR, ¹H, ³¹P{¹H} NMR spectroscopy; their compositions were examined by microanalysis. The luminescent properties of the complexes 1-14 in the solid state are reported.     

Synthesis, characterization of [{(N-methyl-N-benzyl)amino}methyl]ferrocenes and their cyclopalladated complexes: Crystal structure of σ-Pd[(η-C5H5)Fe(η-C5H3CH2N(CH3)CH2C6H4NO2-4)]Cl(PPh3)

Condensation of aminomethylferrocene (1) and substituted benzaldehydes resulted in aldimines 2a-c which followed by reduction with sodium borohydride to give 3a-c. N-methylation of 3a-c with HCHO/NaCNBH₃/HOAc led to 4a-c. Treatment of 4a-c with sodium palladium tetrachloride in the presence of sodium acetate afforded cleanly cyclopalladated 5a-c in which configurations consisted of the R_NR_C, S_NS_C. The preferable activation of C_Ferrocenyl-H bond over C_Phenyl-H bond was also observed. All compounds 2-5 were characterized by elemental analysis, IR and ¹H NMR. In addition, the molecular structure of 5c was confirmed by single crystal X-ray diffraction. The possible mechanism for the formation of 5 was also discussed.     

Investigation on the coordination modes: Syntheses, characterization and crystal structures of diorganotin (IV) dichloride with 4(5)-imidazoledithiocarboxylic acid

A series of diorganotin (IV) complexes of the types of R₂SnCl(SSCC₃H₃N₂) (R = CH₃1, ⁿBu 2, C₆H₅3 and C₆H₅CH₂4), R₂Sn(SSCC₃H₃N₂)₂ (R = CH₃5, ⁿBu 6, C₆H₅7 and C₆H₅CH₂8) and R₂Sn(SSCC₃H₂N₂) (R = CH₃9, ⁿBu 10, C₆H₅11 and C₆H₅CH₂12) have been obtained by reactions of 4(5)-imidazoledithiocarboxylic acid with diorganotin (IV) dichlorides in the presence of sodium ethoxide. All complexes are characterized by elemental, IR, ¹H, ¹³C and ¹¹⁹Sn NMR spectra analyses. Also, the complexes 1, 7 and 9 are characterized by X-ray crystallography diffraction analyses, which reveal that the complex 1 is monomeric structure with five-coordinate tin (IV) atom, the complex 7 is monomeric structure with six-coordinate tin (IV) atom and the complex 9 is one-dimensional chain with five-coordinate tin (IV) atom.     

Pd(II) complexes containing N-alkyl-3-pyridine-5-trifluoromethyl pyrazole ligands: Synthesis, NMR studies and X-ray crystal structures

Palladium [PdCl₂(L)] complexes with N-alkylpyridylpyrazole derived ligands [2-(5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L¹), 2-(1-ethyl-5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L²), 2-(1-octyl-5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L³), and 2-(3-pyridin-2-yl-5-trifluoromethyl-pyrazol-1-yl)ethanol (L⁴) were synthesised. The crystal and molecular structures of [PdCl₂(L)] (L = L², L³, L⁴) were resolved by X-ray diffraction, and consist of monomeric cis-[PdCl₂(L)] molecules. The palladium centre has a typical square-planar geometry, with a slight tetrahedral distortion. The tetra-coordinate metal atom is bonded to one pyridinic nitrogen, one pyrazolic nitrogen and two chlorine ligands in cis disposition. Reaction of L (L², L⁴) with [Pd(CH₃CN)₄](BF₄)₂, in the ratio 1M:2L, gave complexes [Pd(L)]₂(BF₄)₂. Treatment of [PdCl₂(L)] (L = L², L⁴) with NaBF₄ and pyridine (py) and treatment of the same complexes with AgBF₄ and triphenylphosphine (PPh₃) yielded [Pd(L)(py)₂](BF₄)₂ and [Pd(L)(PPh₃)₂](BF₄)₂ complexes, respectively. Finally, reaction of [PdCl₂(L⁴)] with 1 equiv of AgBF₄ yields [PdCl(L⁴)](BF₄).     

Polynuclear nickel (II) and copper (II) complexes of hexaazamacrocycles incorporating pairs of diethylenetriamine subunits separated by aromatic spacers

A series of Ni(II) and Cu(II) complexes of the hexaaza macrocycles, 3,6,9,17,20,23-hexaazatricyclo[23.3.1.1^11,15]triaconta-1(29),11(30),12,14,25,27-hexaene (L¹) and 3,6,9,16,19,22-hexaazatricyclo[22.2.2.2^11,14]triaconta-1(26),11(29),12,14(30),24(28),25-hexaene (L²), have been prepared and the crystal structures determined for [Ni₂L¹(O₂CCH₃)₂(H₂O)₂](ClO₄)₂ (1), [Ni₂L²(DMF)₆](ClO₄)₄ · 2H₂O (2), {[Cu₂L²Br(O₂CCH₃)](ClO₄)₂}_n (3), [Cu₂L²(μ-CO₃)(H₂O)₂]₂(ClO₄)₄ · 8H₂O (4), [Cu₂L²(O₂CCH₃)₂](BF₄)₂ (5), and [Cu₂L¹(μ-imidazolate)Br]₂Br₄ · 6H₂O (6). In these complexes, two metal centers are bound per ligand; in 1 and 3-6, the N₃ subunits of L¹ or L² coordinate meridionally to the metal centers, whilst in 2, each N₃ subunit in L² adopts a facial mode of coordination. The binuclear cations in 1 and 2 have chair-like conformations, with the distorted octahedral Ni(II) coordination spheres completed by terminal water and a bidentate acetate ligand in 1 and three DMF ligands in 2. The Cu(II) centers in 3-6 generally reside in square planar environments, although a weakly binding ligand enters the coordination sphere in some cases, generating a distorted square pyramidal geometry. The binuclear [Cu₂L²]⁴⁺ units in 3, 4 and 5 adopt similar bowl-shaped conformations, stabilized by H-bonding interactions between pairs of amine groups from L² and a perchlorate or tetrafluoroborate anion. In 3, the binuclear units are linked through acetate groups, bridging in a syn-anti fashion, to produce a zig-zag polymeric chain structure, whilst 4 incorporates a tetrameric cation consisting of two binuclear units linked via a pair of carbonate bridges. Compound 6 features an imidazolate bridge between the two Cu(II) centers bound by L¹. Pairs of [Cu₂L¹(μ-imidazolate)]³⁺ units are then weakly linked through a pair of bromide anions.     

Methylated anthocyanidin glycosides from flowers of Canna indica

Methylated anthocyanin glycosides were isolated from red Canna indica flower and identified as malvidin 3-O-(6-O-acetyl-β-d-glucopyranoside)-5-O-β-d-glucopyranoside (1), malvidin 3,5-O-β-d-diglucopyranoside (2), cyanidin-3-O-(6″-O-α-rhamnopyranosyl-β-glucopyranoside (3), cyanidin-3-O-(6″-O-α-rhamnopyranosyl)-β-galactopyranoside (4), cyanidin-3-O-β-glucopyranoside (5) and cyanidin-O-β-galactopyranoside (6) by HPLC-PDA. Their structures were subsequently determined on the basis of spectroscopic analyses, that is, ¹H NMR, ¹³C NMR, HMQC, HMBC, ESI-MS, and UV-vis. Compounds (1-4) were found to be in major quantity while compounds (5-6) were in minor quantity.     

A new entry into ferraborane chemistry: Synthesis and characterization of heteroferraborane complexes

Reaction of [CpFe(CO)₂I], 1 (Cp = η⁵-C₅H₅) and di(organyl)dichalcogenides, E₂R₂ (E = S, Se; R = Ph, CH₂Ph, 2,6-(^tBu)₂-C₆H₂OH) with [LiBH₄·thf] at −70 °C in toluene, followed by stirring at room temperature for 18 h yielded heteroferraboranes, [CpFe(CO)B₂H₄(μ-L)], 2-4 (2: L = SePh; 3: SeCH₂Ph and 4: S(2,6-(^tBu)₂-C₆H₂OH). Compounds 2-4 are highly unstable and concurrent lose of boron atoms yielded organochalcogenolato-bridged complexes, [CpFe(CO)(μ-L)]₂, 5-7, respectively (5: L = SePh; 6: SeCH₂Ph and 7: S(2,6-(^tBu)₂-C₆H₂OH). In contrast, the reaction of 1 with di(2-furyl)ditelluride, (C₄H₃O)₂Te₂, yielded organotellurato-bridged complex, [CpFe(CO)(μ-TeC₄H₃O)]₂, 8 and all of our attempts to isolate the boron precursor [CpFe(CO)B₂H₄(μ-TeC₄H₃O)] in pure form failed. The accuracy of these predictions in each case is established by IR, ¹H, ¹¹B, ¹³C, ⁷⁷Se, ¹²⁵Te NMR and mass spectrometry and complex 8 is further structurally confirmed by X-ray crystallography.     

Effects of steric/basic properties of Lewis bases on the degree of aggregation of zinc(II) pivalate complexes

A triangular [Zn₃(μ₃-OH)(OC(O)^tBu)(μ₂-κ¹O:κ¹O′-O₂C^tBu)₄(3,5-lutidine)₃] (1), a paddlewheel based dinuclear [Zn(μ₂-κ¹O:κ¹O′-O₂C^tBu)₂L]₂ [L = 2,4-lutidine (2), 3,4-lutidine (3), and 2,3-lutidine (4)] and an hourglass based linear trinuclear [Zn₃(μ₂-κ¹O:κ¹O′-O₂C^tBu)₆(pyridine)₂] (5) complexes were synthesized to understand the role of subtle steric/basic properties of Lewis bases on the degree of aggregation of the products. The mononuclear Zn(OC(O)^tBu)₂·2H₂O was also prepared in order to probe the origin of the μ₃-OH moiety in complex 1. Complexes 1-5 and Zn(OC(O)^tBu)₂·2H₂O were characterized by microanalytical, IR, TGA/DTA, solution (¹H and ¹³C) NMR, solid-state cross-polarization magic angle spinning (CP-MAS) ¹³C NMR, mass spectral data and single crystal X-ray diffraction data. Complex 1 represents the first example of a discrete trinuclear zinc(II) carboxylate complex that contains a [Zn₃(μ₃-OH)]⁵⁺ core with zinc atoms in three distinct geometries namely a distorted tetrahedral, trigonal bipyramidal, and octahedral. A plausible mechanism for the formation of complexes 1-5 was explained with the aid of point zero charge (pzc) model.     

Copper(II) complexes with monocarboxylate ligands bearing different substituent groups: Synthesis and spectroscopic studies

In our continuing efforts to explore the effects of substituent groups of ligands in the formation of supramolecular coordination structures, seven new Cu^II complexes formulated as [Cu₂(L¹)₄(DMF)₂] (1), {[Cu₂(L¹)₄(Hmta)](H₂O)_0.75}_∞ (2), [Cu₂(L²)₄(2,2′-bipy)₂] (3), [Cu₂(L³)₄(H₂O)₂] (4), [Cu₂(L³)₄(Hmta)]_∞ (5), [Cu₂(L³)₄(Dabco)]_∞ (6) and [Cu₂(L³)₄(Pz)]_∞ (7) with three monocarboxylate ligands bearing different substituent groups HL¹-HL³ (HL¹ = phenanthrene-9-carboxylic acid, HL² = 2-phenylquinoline-4-carboxylic acid, HL³ = adamantane-1-carboxylic acid, Hmta = hexamethylenetetramine, 2,2′-bipy = 2,2′-bipyridine, Dabco = 1,4-diazabicyclo[2.2.2] octane and Pz = pyrazine), have been prepared and characterized by X-ray diffraction. In 1, 2 and 4-7, each Cu^II ion is octahedrally coordinated, and carboxylate acid acts as a syn-syn bridging bidentate ligand. While each Cu^II ion in 3 is penta-coordinated in a distorted square-pyramidal geometry. 1 and 4 both show a dinuclear paddle-wheel block, while 2, 5, 6 and 7 all exhibit an alternated 1D chain structure between dinuclear paddle-wheel units of the tetracarboxylate type Cu₂-(RCO₂)₄ and the bridging auxiliary ligands Hmta, Dabco and Pz. Furthermore, 3 has a carboxylic unidentate and μ_1,1-oxo bridging dinuclear structure with the chelating auxiliary ligand 2,2′-bipy. Moreover, complexes 1-6 were characterized by electron paramagnetic resonance (EPR) spectroscopy.