Volume 74, Issue 2

The donor-free potassium silanide K[SiPh 3 ] was prepared by the reaction of hexaphenyldisilane, Ph 3 Si–SiPh 3 , with potassium metal in benzene at room temperature. The solid-state structure, determined by powder X-ray diffraction consists of {K[SiPh 3 ]} 2 units, which interact with adjacent dimers to form an infinite chain along the crystallographic c axis (orthorhombic, space group Cmc 2 1 , Z =4). The structure features short contacts between the π system of the phenyl rings and the potassium atoms of neighbouring K[SiPh 3 ] units.

Through the use of two kinds of imidazole derivatives containing different O-functional units, three new Keggin- and one Wells-Dawson-polyoxometalate (POM)-based compounds, namely [Cu 2 L a 4 (HPW 12 O 40 )] ( 1 ), [Cu L a 4 (H 2 O) 2 (HPMo 12 O 40 )] ( 2 ), [Cu 2 L a 7 (H 2 O)(H 2 P 2 W 18 O 62 )]· L a ( 3 ), [Ag 2 ( L b 4 )(HPMo 12 O 40 )]· L b ·H 2 O ( 4 )( L a =  (4-(2,5-dihydro-1 H -imidazol-1-yl)benzaldehyde), and L b =(4-(2,5-dihydro-1 H -imidazol-1-yl)benzoic acid), were synthesized and characterized using single-crystal X-ray diffraction, elemental analyses, and infrared spectroscopy. The polyoxoanions occupy holes framed by two symmetrically oriented Cu L a 2 units in 1 . In compound 2 , the square-planar Cu L a 4 units form a two-dimensional (2D), supramolecular grid through π···π stacking interactions. The POMs occupy vacancies in this grid. In compound 3 , the Cu L a 3 subunits connect the neighboring P 2 W 18 units and an “S”-type chain is formed. Through hydrogen bonding interactions, the chains are connected to form a layer. In compound 4 , the POM anions are linked by Ag L b 2 subunits to form a chain. All the chains are tied together to construct a layer structure with weak hydrogen bonding interactions between the terminal carboxylic acid functional groups of ligands L b . The electrocatalytic and photocatalytic activities of all these four compounds were also studied.

The complex Ag(I)(flavonolate)(PPh 3 ) 2 has been prepared and characterized including the crystal structure. This compound shows in degassed solution two emission bands, a fluorescence at λ max =505 nm and a phosphorescence at λ max =780 nm. Both emissions originate from lowest-energy flavonolate intraligand excited singlet and triplet states, respectively. In the presence of oxygen, the phosphorescence disappears and the complex becomes light-sensitive. The flavonolate ligand undergoes a photooxidation by oxygen.

Some new 7-alkyl-4,6-dihydropyrazolo[4′,3′:5,6]pyrano[2,3- d ]pyrimidin-5(1 H )-ones were prepared through heterocyclization of 6-amino-1,4-dihydropyrano[2,3- c ]pyrazole-5-carbonitriles with aliphatic carboxylic acids in the presence of phosphoryl chloride under reflux in high yields. The suggested mechanism involves a tandem intramolecular Pinner–Dimroth rearrangement. The products were characterized on the basis of FT-IR, 1 H NMR, and 13 C NMR spectral and microanalytical data and evaluated for their antibacterial activity against Gram-positive bacteria ( Staphylococcus aureus and Staphylococcus epidermidis ) and Gram-negative bacteria ( Escherichia coli and Pseudomonas aeruginosa ) using the disk diffusion method.

The total synthesis of the natural phytoalexin 2,6-dimethoxy-9-phenyl-1 H -phenalen-1-one ( 3) isolated from Eichhornia crassipes was accomplished in seven steps. The synthetic strategy included a Friedel–Crafts acylation and a Jacobsen–Katsuki epoxidation as the key reactions to obtain the target compound. Based on a comparison of the NMR data and a crystal structure of 3 , the previously proposed structure of 2,5-dimethoxy-4-phenyl-benzoindenone ( 2) isolated from the same plant has been revised.

The Michael addition of enaminoesters to coumarins leads to the formation of the rearranged adduct 1 whose structure has been previously elucidated by X-ray crystallographic analysis. Now, N- and/or O- carbamoylation of the 6-amino-2-pyridone 1 by treatment with phenyl isocyanate in a molar ratio of 1:1 and 1:2 gave N -mono- ( 2a ) or N,O -bis-(phenylcarbamoyl) ( 3 ) derivatives, respectively. Further transformations of the corresponding new 2-pyridone derivative 2a into the O- acetyl derivative 2b and the chromeno[3,4- c ]pyridine 4 are reported as well.

From an ethyl acetate extract of twigs and barks of Dacrydium elatum a new diterpenoid named dacrydianone ( 1 ), together with lambertic acid ( 2 ), three ecdysteroids: 20-hydroxyecdysone ( 3 ), ajugasterone C ( 4 ), ponasterone A ( 5 ), and daucosterol ( 6 ), has been isolated. Their structures were elucidated by an extensive analysis of the UV/Vis, FT-IR, MS and NMR spectra as well as comparison with those in published literature. The EtOAc extract and the isolated compounds 1–5 were evaluated for their cytotoxicity on four cancer cell lines: breast cancer (MCF-7), lung cancer (Lu-1), liver cancer (HepG2) and human oral cancer (KB). The EtOAc extract and compound 2 showed a medium activity on four tested cancer cell lines, while compounds 3 and 5 exhibited week activity on these cell lines. Compounds 1 and 4 did not show activity on the tested cell lines.

Single crystals of the high-temperature modification of RhSn 4 were obtained from a tin flux (1:20 molar ratio; final annealing at 920 K; dissolution of the tin matrix in 2N HCl). The structure was refined from single-crystal X-ray diffractometer data: I 4 1 / acd , a =629.73(5), c =2288.36(18) pm, wR 2=0.0382, 447 F 2 values and 14 variables. β -RhSn 4 is isotypic with β -IrSn 4 . The rhodium atoms have slightly distorted square-antiprismatic tin coordination with Rh–Sn distances of 4×273.4 and 4×274.1 pm. The RhSn 8 units are condensed via common edges to layers that are staggered with respect to each other and stacked in ABCD sequence. A 119 Sn Mössbauer spectroscopic characterization of ß -RhSn 4 and the stannides RhSn 3 and α -RhSn 4 shows the typical isomer shifts for transition metal stannides. Only for α -RhSn 4 the three crystallographically independent tin sites could be resolved, a consequence of the different s -electron density. Treatment of α -RhSn 4 under high-pressure (up to 10 GPa)/high-temperature (up to T =1370 K) conditions leads to decomposition into Rh 1.5 Sn, RhSn 2 and β -Sn.

The equiatomic iron-silicides T FeSi as well as the corresponding germanides T FeGe with the electron-poor 4 d and 5 d transition metals ( T =Zr, Nb, Hf, Ta) have been synthesized from the elements by arc-melting. All samples were characterized through their lattice parameters using powder X-ray diffraction (Guinier technique). Four structures were refined from single-crystal X-ray diffractometer data: a =640.16(3), b =393.45(5), c =718.42(6) pm, Pnma , 390 F 2 values, 20 parameters, wR 2=0.0294 for ZrFeSi (TiNiSi type), a =719.63(11), b =1119.27(7), c =649.29(7) pm, Ima 2, 1103 F 2 values, 54 parameters, wR 2=0.0555 for NbFeGe (TiFeSi type), a =655.96(7), c =372.54(4) pm, P 6̅2 m , 251 F 2 values, 15 parameters, wR 2=0.0260 for HfFeGe (ZrNiAl type) and a =624.10(3), b =378.10(6), c =725.25(7) pm, Pnma , 369 F 2 values, 20 parameters, wR 2=0.0513 for TaFeGe (TiNiSi type). The common structural motif of the four different structures is the slightly distorted tetrahedral tetrel ( tr ) coordination of the iron atoms and a trigonal prismatic coordination of iron by T =Zr, Nb, Hf, Ta. Three compounds were characterized as Pauli-paramagnetic by measuring their susceptibility. The measurement of the electrical resistivity of NbFeSi characterises this compound as a good metal. Furthermore, 57 Fe Mössbauer spectra of all compounds could be obtained at room temperature, revealing a clear correlation between the structural distortions and the quadrupole splitting parameters.

The reaction of carbon monoxide with the acyclic diaminocarbene i Pr 2 N–C–TMP (TMP=2,2,6,6-tetramethylpiperidino), generated in situ from the formamidinium salt [( i Pr 2 N)CH(TMP)][PF 6 ] and NaN(SiMe 3 ) 2 , unexpectedly afforded a mixture of β - and γ -lactams.

The plumbides RE ZnPb ( RE =rare earth metals La–Nd and Sm–Tb) were synthesized by induction melting of the elements in sealed niobium ampoules. The samples were characterized by X-ray powder diffraction. The structures of the praseodymium and neodymium compound were refined from single-crystal X-ray diffractometer data: YPtAs type, P 6 3 / mmc , a =461.32(8), c =1658.00(3) pm, wR 2=0.0588, 267 F 2 values, 12 variables for PrZnPb and a =460.12(3), c =1642.7(1), wR 2=0.0617, 243 F 2 values, 12 variables for NdZnPb. The plumbides with RE =La, Ce, Sm, Gd and Tb are isotypic while the Zintl phase EuZnPb crystallizes with the orthorhombic TiNiSi type, Pnma , a =796.6(2), b =482.53(9), c =822.9(2) pm. The zinc and lead atoms build up polyanionic networks: slightly puckered Zn 3 Pb 3 layers in AA′BB′ stacking sequence in the YPtAs type plumbides and a three-dimensional [ZnPb] 2− network with distorted tetrahedral ZnPb 4/4 coordination in EuZnSn. The different crystal structures are a consequence of the valence electron count, i.e. 18 for EuZnSn and 19 for the hexagonal plumbides. The crystal chemical details and bonding peculiarities are discussed.

Thioether-functionalized aminosilanes R 2 Si(NH-C 6 H 4 -2-SR′) 2 with R=Me, Ph and R′= t -Bu, Me, Ph were synthesized from the corresponding dichlorosilanes R 2 SiCl 2 and lithiated aniline derivatives LiNH-C 6 H 4 -2-SR′. Treatment of the functionalized aminosilanes R 2 Si(NH-C 6 H 4 -2-SR′) 2 with two eq. of n -BuLi and subsequent reaction with nickel(II) halides NiX 2 (X=Cl, Br) or [Ni(acac) 2 (TMEDA)] led to the formation of the Ni(II) complexes [Ni{R 2 Si(N-C 6 H 4 -2-SR′) 2 }]. The X-ray single-crystal structure determinations of the nickel complexes revealed that the thioether-functionalized silylamides R 2 Si(NC 6 H 4 -2-SR′) 2 2− act as tetradentate ligands. The nickel atoms exhibit a distorted square-planar coordination with Ni–N and Ni–S bond lengths in the range of 186.4(3)–186.9(2) pm and 217.5(1)–221.5(1) pm, respectively.