Perrhenate ion uptake by aluminium hydroxide gels

The adsorption of perrhenate ions onto aluminium hydroxide gels was investigated. These gels were prepared by the sol-gel method in non aqueous solutions using a tertiary amine as template. They were amorphous and presented high specific surface areas. The amount of perrhenate ions adsorbed from aqueous solutions depended on the specific surface area of the gels. Removal of perrhenate ions up to 84% could be achieved without reaching saturation.     

Preconcentration of trace elements by aluminium hydroxide

Summary Coprecipitation of traces of cobalt, zinc, chromium, ruthenium and mercury with freshly precipitated aluminium hydroxide has been investigated by a radiotracer method. Investigations were performed over a wide range of pH. The results indicate that traces of cobalt, zinc and chromium could be almost completely coprecipitated between pH 6 and 10. On the other hand coprecipitation yield for ruthenium in this pH range do not exceed 95%, which is believed to be the consequence of the various physicochemical states of ruthenium. The coprecipitation yields for mercury are very low as a consequence of the presence of non-ionized HgCl₂.

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Zusammenfassung Die Mitfällung von Spuren Kobalt, Zink, Chrom, Ruthenium und Quecksilber mit frisch gefälltem Aluminiumhydroxid wurde radiochemisch untersucht. Die dazu nötigen Experimente erstreckten sich über ein weites pH-Gebiet. Die Ergebnisse zeigen, daß Spuren Kobalt, Zink und Chrom zwischen pH 6 und 10 fast vollständig mitgefällt werden konnten. Andrerseits sind die Mitfällungsausbeuten für Ruthenium in diesem pH-Gebiet nicht größer als 95%, was vermutlich die Folge der verschiedenen physikalischchemischen Zustände des Rutheniums ist. Die Mitfällungsausbeuten für Queckilber sind infolge der nur geringen Dissoziation des HgCl₂ sehr gering.

     

Paramagnetic centers by X-ray-irradiation of aluminium hydroxide

EPR spectra of paramagnetic centers originating from X-ray-irradiation of aluminium hydroxide at room temperature have been measured. The EPR spectrum represents a superposition of EPR spectra of ionic centers O^–, holes of type and trapped electrons. Radiation chemical yield of paramagnetic centers observed at room temperature (293 K) is G(spins.)=4.4±0.6) spins per 100 eV absorbed energy. The decay of paramagnetic centers in irradiated Al(OH)₃ was oberved at 293 K. The rate constant of the paramagnetic centers decay in irradiated Al(OH)₃ is K₂=(0.0980±0.0019) kg·mol^–1·min^–1 and their half-life is 9.43±0.18 days.Dedicated to the memory of the late Genrikh Markovis Kolyiari.     

A novel dimeric zinc(II) complex with a tripodal peptide ligand: a structure stabilized by ligand sharing

The crystal structure of a novel dimeric zinc(II) complex, [ZnL(H₂O)]₂(ClO₄)₂·4H₂O (L?=?N-(bis(2-pyridyl)methyl)-2-pyridinecarboxamide), has been determined by X-ray diffraction. In this complex each planar N_py–N_amido–N_py moiety of the ligand coordinates to one zinc ion and the pendant pyridine of one [ZnL] unit completes the coordination sphere of a [ZnL] neighbor. Units of the complex are connected in a two-dimensional network by intermolecular hydrogen bonds. The thermodynamic properties of the ligand with bivalent metal ions Co(II), Ni(II), Cu(II) and Zn(II) were studied by potentiometric titration and the order of the stability constants is in agreement with the Irving–Williams series. The dimeric complex is stabilized through ligand sharing, as confirmed by the crystal structure and thermodynamic properties.     

A tetrameric neptunyl(v) cluster supported by a Schiff base ligand

The first tetrameric cation-cation neptunyl(v) cluster, [{NpO(2)(salen)}(4)(μ(8)-K)(2)][K(18C6)Py](2), has been synthesized in non-aqueous solution from the reaction of [(NpO(2)Py(5))(KI(2)Py(2))](n) with K(2)salen and its structure determined in the solid state and in solution where the complex retains its tetrameric form.     

Kinetics of aluminium hydroxide dehydration

Non-isothermal thermogravimetric analysis was used for determination of the kinetics of aluminium hydroxide dehydration in an air atmosphere and for processing of the experimental results by the method due to Chatterjee.Aluminium hydroxide dehydration proceeds according to the following mechanism: Al(OH)₃AlOOH + H₂O 2 AlOOHAl₂O₃ + H₂OBoth reactions proceed in the diffusion region, the first up to 526 K and the second up to 700 K, and the corresponding activation energy values are 15.7 and 0.2 kJ/mole, respectively.

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Zusammenfassung Die nicht-isotherme thermogravimetrische Analyse wurde zur Bestimmung der Kinetik der Dehydration von Aluminiumhydroxid in Luft-Atmosphäre eingesetzt und die Methode von P. K. Chatterjee zur Verarbeitung der Versuchsergebnisse angewendet.Der Dehydratisierungsvorgang von Aluminiumhydroxid verläuft nach folgendem Mechanismus: Al(OH)₃AlOOH + H₂O 2 AlOOHAl₂O₃ + H₂OBeide Reaktionen spielen sich in der Diffusionszone ab, die erstere bis zur Temperatur von 526 K und die zweite bis zur Temperatur von 700 K. Die entsprechenden Aktivierungsenergien sind 15.70 kJ/Mol für die erste und 0.20 kJ/Mol für die zweite Reaktion.Bei kontinuierlicher Erhöhung der Temperatur über 526 K im ersten und über 700 K im zweiten Fall werden die Geschwindigkeiten dieser Reaktionen durch kristallchemische Umwandlungen begrenzt und die Aktivierungsenergie beträgt 116.97 kJ/Mol für die erste und 91.92 kJ/Mol für die zweite Reaktion.

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Résumé On détermine la cinétique de la déshydratation de l'hydroxyde d'aluminium dans l'air, par thermogravimétrie non-isotherme, en dépouillant les résultats suivant la méthode proposée par P. K. Chatterjee.Le processus de la déshydratation de l'hydroxyde d'aluminium s'effectue suivant le mécanisme: Al(OH)₃AlOOH + H₂O 2AlOOHAl₂O₃ + H₂OLes deux réactions ont lieu par diffusion, la première jusqu'à la température de 526 K et la seconde jusqu'à 700 K, les valeurs correspondantes des énergies d'activation étant 15.70 kJ · mol^–1 pour la première et 0.20 kJ · mol^–1 pour la seconde réaction.Lors d'une élévation continue de la température au-dessus de 526 K dans le premier cas et au-dessus de 700 K dans le deuxième cas, les vitesses de ces réactions deviennent limitées en raison des transformations cristallochimiques et les valeurs des énergies d'activation sont 116.97 pour la première et 91.92 kJ · mol^–1 pour la seconde réaction.

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, — . : Al(OH)₃AlOOH + H₂O 2 AlOOHAl₂O₃ + H₂O , 526 , — 700 . 15,70 0,20 / . 526 700 — , - , , 116,97 91,92 /.

     

Scandium arene inverted-sandwich complexes supported by a ferrocene diamide ligand

The synthesis and characterization of the first scandium arene inverted-sandwich complexes supported by a ferrocene diamide ligand (NN(fc)) are reported. Through the use of (NN(fc))ScI(THF)(2) as a precursor and potassium graphite (KC(8)) as a reducing agent, the naphthalene and anthracene complexes [(NN(fc))Sc](2)(μ-C(10)H(8)) and [(NN(fc))Sc](2)(μ-C(14)H(10)), respectively, were synthesized and isolated in moderate to high yields. Both molecular structures feature an inverted-sandwich geometry and exhibit short Fe-Sc distances. DFT calculations were employed to gain understanding of the electronic structures of these new scandium arene complexes. A variable-temperature NMR spectroscopic study of [(NN(fc))Sc](2)(μ-C(14)H(10)) indicated that two different structures are accessible in solution. Reactivity studies showed that the naphthalene complex [(NN(fc))Sc](2)(μ-C(10)H(8)) can be converted to the corresponding anthracene species [(NN(fc))Sc](2)(μ-C(14)H(10)) and that [(NN(fc))Sc](2)(μ-C(10)H(8)) can act as either a reductant or a proton acceptor. The reaction of [(NN(fc))Sc](2)(μ-C(10)H(8)) with excess pyridine led to a rare example of C-C bond formation between two pyridine rings at the para position.     

Lithium and aluminium complexes supported by chelating phosphaguanidinates

Diisopropylcarbodiimide, (i)PrN[double bond, length as m-dash]C[double bond, length as m-dash]N(i)Pr, inserts into the lithium-phosphorus bond of in situ prepared "Ph(2)PLi(THF)(n)" to afford the lithium salt, [Li(Ph(2)PC{N(i)Pr}(2))(THF)(n)](x)(2a); alternatively, this compound can be made by deprotonation of the neutral phosphaguanidine, Ph(2)PC{N(i)Pr}{NH(i)Pr}(1a) with (n)BuLi. Displacement of the THF solvate in 2a is readily achieved with TMEDA to afford Li(Ph(2)PC{N(i)Pr}(2))(TMEDA)(3a). X-Ray crystallographic analyses show that 2a exists as a dimer in the solid state with a folded ladder structure and an N,N' chelating phosphaguanidinate, while 3a is monomeric with N,P-coordination of the ligand to lithium. Compound 2a reacts via a transmetallation pathway with AlMe(2)Cl to afford the dimethylaluminium complex, Al(Ph(2)PC{N(i)Pr}(2))Me(2)(4a), which can also be prepared by protonation of a methyl group of AlMe(3) using 1a. The formation of a series of dialkylaluminium compounds has been investigated employing this latter pathway using both 1a and the N,N'-dicyclohexyl analogue, Ph(2)PC{NCy}{NHCy}(1b), affording Al(Ph(2)PC{NR}(2))Et(2)(5a,b), Al(Ph(2)PC{NR}(2))(i)Bu(2)(6a,b) and the diphenylaluminium compound Al(Ph(2)PC{N(i)Pr}(2))Ph(2)(7a). The oily nature of most of the dialkyl compounds and high sensitivity to oxygen and moisture lead to difficulty in manipulation and characterization; however, NMR spectroscopy indicated highly pure products (>95%) upon removal of the solvent. The molecular structures of the crystalline examples 4a and 7a are reported, showing monomeric aluminium species with symmetrically chelating phosphaguanidinate ligands. The series of aluminium compounds AlLCl(2){L=[EC{NiPr}(2)](-): A, E=Me; B, E=Me(2)N; C, E=(Me(3)Si)(2)N and D, E=Ph(2)P} were investigated using density functional theory. In the more simple cases A and B, the delocalized electron density of the metallacycle was represented by a combination of the HOMO and an orbital of lower energy (A, HOMO-5; B, HOMO-6). The HOMO-1 in B was pi-bonded across the Me(2)N-C bond suggesting delocalization of electron density into the metallacycle. In the more complex systems C and D, delocalization within the metallacycle was less extensive due to the (Me(3)Si)(2)N- and Ph(2)P-moieties. A number of occupied orbitals in D, however, display phosphorus 'lone-pair' characteristics, indicating that these species have the potential to behave as Lewis bases in the formation of poly(metallic) systems.     

Transmetalation reactions of a scandium complex supported by a ferrocene diamide ligand

Efforts to transfer to aluminum the heterocyclic ligand of a ring-opened imidazole scandium complex, which was previously reported, are presented. A ring-opened imidazole aluminum compound was formed at 50 °C and characterized as a trialuminum complex. At high temperature (85 °C), the formation of an unusual scandium/aluminum methylidene was observed. The reaction products were characterized by standard spectroscopic techniques and X-ray crystallography. Density functional theory calculations were used to understand the electronic structure of the scandium/aluminum methylidene complex.     

A new heteroleptic phosphorescent cuprous complex supported by a BINAP ligand: synthesis,structure, luminescence properties and theoretical analyses

Luminescent cuprous complexes are an important class of coordination compounds due to their relative abundance, low cost and ability to display excellent luminescence. The heteroleptic cuprous complex solvate rac‐(acetonitrile‐κN)(3‐aminopyridine‐κN)[2,2′‐bis(diphenylphosphanyl)‐1,1′‐binaphthyl‐κ²P,P′]copper(I) hexafluoridophosphate dichloromethane monosolvate, [Cu(C₅H₆N₂)(C₂H₃N)(C₄₄H₃₂P₂)]PF₆·CH₂Cl₂, conventionally abbreviated as [Cu(3‐PyNH₂)(CH₃CN)(BINAP)]PF₆·CH₂Cl₂, ( I ), where BINAP and 3‐PyNH₂ represent 2,2′‐bis(diphenylphosphanyl)‐1,1′‐binaphthyl and 3‐aminopyridine, respectively, is described. In this complex solvate, the asymmetric unit consists of a cocrystallized dichloromethane molecule, a hexafluoridophosphate anion and a complete racemic heteroleptic cuprous complex cation in which the cuprous centre, in a tetrahedral CuP₂N₂ coordination, is coordinated by two P atoms from the BINAP ligand, one N atom from the 3‐PyNH₂ ligand and another N atom from a coordinated acetonitrile molecule. The UV–Vis absorption and photoluminescence properties of this heteroleptic cuprous complex have been studied on polycrystalline powder samples, which had been verified by powder X‐ray diffraction before recording the spectra. Time‐dependent density functional theory (TD‐DFT) calculations and a wavefunction analysis reveal that the orange–yellow phosphorescence emission should originate from intra‐ligand (BINAP) charge transfer mixed with a little of the metal‐to‐ligand charge transfer ³(IL+ML)CT excited state.     

Crystallization processes in aluminium hydroxide gels

Summary Changes in specific surface area, interpreted in conjunction withX-ray powder diffraction and electron microscopy, have been used to follow the formation of pseudoboehmite and bayerite from amorphous aluminium hydroxide. Precipitates, essentially free from foreign ions, were prepared by the hydrolysis of aluminium s-butoxide and ageing in water, aqueous ethanol and aqueous glycerol was studied. A comparison of rates of crystallization in these media provides evidence for the idea that pseudoboehmite is formed by an inter- and intra-particle condensation involving hydroxyl groups while bayerite is formed by a dissolution and recrystallization process. Possible rate determining factors in these mechanisms are considered and the role of particle aggregation-cementation, the degree of which depends on the nature of the solvent, is discussed.

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Zusammenfassung Änderungen in der spezifischen Oberfläche interpretiert in Verbindung mit Röntgenbeugung und elektronenmikroskopischen Aufnahmen wurden angewendet, um die Bildung von Pseudoböhmit und Bayerit aus amorphem Aluminiumhydroxid zu verfolgen. Die ausgefällten Produkte, im wesentlichen frei von Fremdionen, wurden durch Hydrolyse von Aluminium-s-butoxid und Alterung in Wasser, wäßrigem Äthanol und wäßrigem Glycerin untersucht. Ein Vergleich der Kristallisationsgeschwindigkeiten in diesen Medien legt nahe, daß Pseudoböhmit durch eine inter- und intra-Teilchenkondensation durch Hydroxylgruppen gebildet wird, während Bayerit durch Lösungs-und Rekristallisationsprozesse entsteht. Mögliche geschwindigkeitsbestimmende Faktoren dieser Mechanismen werden betrachtet, und die Rolle der Partikel-verklebung, deren Ausmaß von der Natur des Lösungsmittels abhängt, wird diskutiert.

     

Studies on recrystallised aluminium hydroxide precipitates

Summary Aluminium hydroxide gels were recrystallised in high pH solution for 2–1000 h to give a series of Gibbsite powdersP11/2,P11/8,P1/48,P11/360 andP11/X, consisting of hexagonal platelet crystals; their average platelet lengths (l ₀) were 0.03, 0.06, 0.13, 0.26 and 0.45 microns. The dissolution of dilute suspensions of these powders in well-stirred sodium hydroxide solutions were studied at 20–65°C Reaction solid and solution were analysed after different times by chemical and physical methods.Reaction occurred by two-directional dissolution of the platelet crystals. The reactions of GibbsiteP11/X (prepared by prolonged 1000 h crystallisation) were first order w.r.t. powder weight (and second order w.r.t. powder effective surface area); the reactions of the other Gibbsites were first order for the first twenty percent rapid dissolution and then slower. The initial rate constantsk _w1 (h^–1) and half-lifest _0.5 (h) for reactions ofP11/2,P11/8,P11/48.P11/360 andP11/X with sodium hydroxide solution of unit mean ionic activity at 20°C were 1.70, 0.9; 0.60, 2.2; 0.22, 5.5; 0.07, 14 and 0.02, 38 respectively.Rate constants increased linearly with the mean ionic activity of the hydroxide solution and increased exponentially with reciprocal absolute temperature, four to five times for 15°C temperature rise. Half-lifes decreased in a similar manner. Energies of activation varied from 76–83 kJ/mol. The rates of dissolution are determined by the rate of the chemical reaction between adsorbed hydroxyl ions and adjacent reactive aluminium hydroxide sites on the powder crystal surface.

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Zusammenfassung Aluminiumhydroxydgele werden in Lösungen höher pH 2 bis 1000 Std. rekristallisiert und ergeben dabei eine Reihe von Gibbsit-PulverP11/2,P11/8,P11/48,P11/360 undP11/X. Sie bestehen aus hexagonalen plättchen-förmigen Kristallen. Die mittlere Dimension (l ₀) waren 0,03; 0,06; 0,13; 0,26 und 0,45 microns. Die Auflösung von verdünnten Suspensionen dieser Pulver wurden in stark gerührten Natriumhydroxyd-Lösungen bei 20 bis 65°C untersucht. Das feste Reaktionsprodukt und die Lösung wurden nach verschiedenen Zeiten mit chemischen und physikalischen Methoden analysiert.Die Reaktion erfolgte durch zwei-dimensionale Auflösung der Blättchen. Die Reaktion von GibbsitP11/X (präpariert durch eine auf 1000 Std. verlängerte Kristallisation) waren von 1. Ordnung hinsichtlich Pulver-gewicht, und von 2. Ordnung hinsichtlich effektiver Oberfläche. Die Reaktion der anderen Gibbsite waren von 1. Ordnung für die ersten 20% schnelle Lösung und wurden dann langsamer. Die anfänglichen Reaktionskonstanten und Halbzeiten der Auflösung für alle Gibbsite in Natriumhydroxyd-Lösungen der Ionenstärke 1 waren 1,70; 0,9, 0,60; 2,2; 0,22; 5,5; 0,07; 14 und 0,02, 38. Zahlen in der ReihenfolgeP11/2 bisP11/X.Die Geschwindigkeitskonstanten wachsen linear mit der mittleren Ionenaktivität der Hydroxylödung und wachsen exponentiell mit der reziproken absoluten Temperatur auf das Vier- oder Fünffache für 15°C Temperaturanstieg. Die Halblebensdauern nehmen in analoger Weise ab. Die Aktivierungsenergien variieren zwischen 76 und 83 kJ/mol. Die Geschwindigkeiten der Auflösungen. werden durch die Geschwindigkeit der chemischen Reaktion bestimmt. Zwischen den adsorbierten Hydroxyd-Ionen und den anhaftenden reaktiven Aluminiumhydroxydplätzen an der Kristall-Pulver-Oberfläche.

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With 6 figures and 2 tables     

Sigma-organyl complexes of ruthenium and osmium supported by a mixed-donor ligand

A series of vinyl, aryl, acetylide and silyl complexes [Ru(R)(kappa2-MI)(CO)(PPh3)2] (R = CH=CH2, CH=CHPh, CH=CHC6H4CH3-4, CH=CH(t)Bu, CH=2OH, C(C triple bond CPh)=CHPh, C6H5, C triple bond CPh, SiMe2OEt; MI = 1-methylimidazole-2-thiolate) were prepared from either [Ru(R)Cl(CO)(PPh3)2] or [Ru(R)Cl(CO)(BTD)(PPh3)2](BTD = 2,1,3-benzothiadiazole) by reaction with the nitrogen-sulfur mixed-donor ligand, 1-methyl-2-mercaptoimidazole (HMI), in the presence of base. In the same manner, [Os(CH=CHPh)(kappa2-MI)(CO)(PPh3)2] was prepared from [Os(CH=CHPh)(CO)Cl(BTD)(PPh3)2]. The in situ hydroruthenation of 1-ethynylcyclohexan-1-ol by [RuH(CO)Cl(BTD)(PPh3)2] and subsequent addition of the HMI ligand and excess sodium methoxide yielded the dehydrated 1,3-dienyl complex [Ru(CH=CHC6H9)(kappa2-MI)(CO)(PPh3)2]. Dehydration of the complex [Ru(CH=CHCPh2OH)(kappa2-MI)(CO)(PPh3)2] with HBF4 yielded the vinyl carbene [Ru(=CHCH=CPh2)(kappa2-MI)(CO)(PPh3)2]BF4. The hydride complexes [MH(kappa2-MI)(CO)(PPh3)2](M = Ru, Os) were obtained from the reaction of HMI and KOH with [RuHCl(CO)(PPh3)3] and [OsHCl(CO)(BTD)(PPh3)2], respectively. Reaction of [Ru(CH=CHC6H4CH3-4)(kappa2-MI)(CO)(PPh3)2] with excess HC triple bond CPh leads to isolation of the acetylide complex [Ru(C triple bond CPh)(kappa2-MI)(CO)(PPh3)2], which is also accessible by direct reaction of [Ru(C triple bond CPh)Cl(CO)(BTD)(PPh3)2] with 1-methyl-2-mercaptoimidazole and NaOMe. The thiocarbonyl complex [Ru(CPh = CHPh)Cl(CS)(PPh3)2] reacted with HMI and NaOMe without migration to yield [Ru(CPh= CHPh)(kappa2-MI)(CS)(PPh3)2], while treatment of [Ru(CH=CHPh)Cl(CO)2(PPh3)2] with HMI yielded the monodentate acyl product [Ru{eta(1)-C(=O)CH=CHPh}(kappa2-MI)(CO)(PPh3)2]. The single-crystal X-ray structures of five complexes bearing vinyl, aryl, acetylide and dienyl functionality are reported.     

Latent low-coordinate titanium imides supported by a sterically encumbering beta-diketiminate ligand

Addition of an equal molar quantity of R- (R = Me, SiMe3) to complex (Nacnac)Ti=NAr(OTf) (Nacnac- =[ArNC(tBu)]2CH, Ar = 2,6-iPr2C6H3) forms the imido alkyl (Nacnac)Ti=NAr(R), which can be readily protonated to afford [(Nacnac)Ti=NAr(L)]+ (L = THF, Et2O, eta1-C6H5NMe2), or treated with B(C6F5)3 to afford the zwitterion (Nacnac)Ti=NAr(micro-CH3)B(C6F5)3.     

An N,N'-chelated phosphenium cation supported by a beta-diketiminate ligand

The first example of a phosphenium cation supported by N,N'-chelation of a beta-diketiminate ligand has been prepared and structurally characterized.     

Dicopper-dioxygen complex supported by asymmetric pentapyridine dinucleating ligand

A dicopper(I) complex supported by a novel asymmetric pentapyridine dinucleating ligand, consisting of tetradentate and tridentate metal-binding sites, has been synthesized and characterized. The dicopper(I) complex reacted with molecular oxygen at a low temperature to give an unprecedented mu-peroxo dicopper(II) complex presumably having a mu-eta1:eta2 binding mode, the spectroscopic features and the reactivity of which have been explored in detail.     

A terminal palladium fluoride complex supported by an anionic PNP pincer ligand

A terminal palladium (II) fluoride complex (^FPNP)PdF (where ^FPNP is a an anionic fluoro-substituted diarylamido/bis(phosphine) pincer ligand) has been prepared and characterized spectroscopically and structurally. An X-ray diffraction study revealed an approximately square-planar environment about Pd and a short Pd-F bond distance. (^FPNP)PdF reacted with silanes containing electron-withdrawing groups on Si by exchange of fluoride with one of the substituents on Si. An analysis of the ¹⁹F chemical shifts of both the Pd-bound fluoride and of the fluorines on the backbone of the ^FPNP ligand is provided.     

A new dimeric diarylpropane from Horsfieldia tetratepala

Five compounds, including a new dimeric diarylpropane, were isolated from the petroleum ether extract of the twigs and leaves of Horsfieldia tetratepala. The structures of these compounds were elucidated by spectroscopic analysis. Moreover, the antiproliferative activities of these compounds were tested on cancer cell lines, but none is active.