The understanding of structure and bonding in intermetallic phases still lags behind that of molecular compounds. For that reason, exploring intermetallic phases and identifying structural patterns and relationships are particularly important for closing this knowledge gap. In particular, here we report on the addition of increasing amounts of platinum to ∼2:1 mixtures of tin and neodymium, which yields eight ternary Pt/Sn/Nd compounds, four of which have not been reported before. Interestingly, except for PtSnNd (1), all observed ternary phases of the system can be derived from the binary compounds Sn2Nd and Sn5Nd2 by adding Pt to the composition(s), as they lie on or close to two lines: Sn2Nd-Pt (Pt0.21(1)Sn2Nd (2), PtSn2Nd (3), Pt1.33Sn2Nd (4), Pt2-xSn2+xNd (x = 0.27(3), 5), and Pt3Sn2Nd (6)) or Sn5Nd2-Pt (Pt1.5Sn5-xNd2 (x = 0.16(2), 7) and Pt3Sn5Nd2-x (x = 0.161(8), 8)). While the introduction of increasing amounts of Pt to the binaries Sn2Nd and Sn5Nd2 leads to stepwise changes in the coordination environment of Nd, Pt preserves its coordination over the entire system in the form of interpenetrating bipyramidal {PtSn5Nd5} clusters.

The rare earth (oxides), R2O3, may be converted into trihalides, RX3, by a number of different synthetic routes of which the ammonium halide route is inexpensive and easy to perform. It runs through ternary ammonium rare-earth halides, e.g. (NH4)3YCl6, and, with sufficient care, avoids the formation of oxide-halides, e.g. YOCl. Nevertheless the formation usually thought as a pitfall, can be a blessing, as the first synthesis of {OYb4}Cl6 attests. Again, there is a number of methods to reduce trihalides to lower oxidation states, most prominently to the divalent state. Binary dihalides, RX2, as well as ternaries such as ARX3, are either prepared by comproportionation or metallothermic reduction reactions, to name the two most prolific routes. Further reduction results in metal-rich halides, of which the most abundant are (complex) octahedral cluster halides, in most cases sequestering a main-group (E) or transition metal (T) atom to overcome the electron paucity of group 3 rare-earth metal atoms R. Clusters in cluster halides with endohedral atoms, e.g. [{PtPr6}I12]Pr, may be isolated or connected through common edges to oligomers, chains, layers or even to three-dimensional structures. Crystal growth is conveniently achieved from rare-earth halide melts. These halide fluxes can be reactive, hence produce complex cluster halides with endohedral atoms, or non-reactive and act as a medium for crystal growth of (polar) intermetallics, e.g. {Pt3Pr4} from a PrCl3 flux. Alternative innocent fluxes can be alkali-metal halides; reactive fluxes such as tin produce ternary intermetallics, e.g. {PtSn2}Nd.Download : Download high-res image (215KB)Download : Download full-size image

A multi-gram synthetic route to black solid {CSc6}I12Sc (1) was developed which comprises the reaction of scandium triiodide, ScI3, with graphite and scandium metal at 850°C. Compound 1 dissolved in N,N-dimethylacetamide (DMA) to form a red solution. Results derived from 45Sc NMR and EPR spectroscopy indicated that a scandium cluster species exists in this solution along with a complex cation [Sc(DMA)6]3+. From these solutions crystals of [Sc(DMA)6]I3 (2) and a red oily product was isolated. Compound 2 was also prepared independently by dissolving ScI3 in DMA and two polymorphs, orthorhombic 2O and monoclinic 2M were crystallised. {CSc6}I12Sc (1) also dissolved in THF yielding a red solution which contains [ScI6]3− and a scandium cluster species, as analysed by 45Sc NMR and EPR spectroscopy.

Starting generally with a 4:6:3 molar ratio of Pt, Sn, and R (where R = La-Sm), with or without the application of a NaCl flux, seven ternary compounds were obtained as single crystals. The platinides Pt4Sn6R3 (R = La-Nd) crystallize with the Pt4Ge6Pr3 type of structure (oP52, Pnma, a = 27.6-27.8 Å, b = 4.59-4.64 Å, c = 9.33-9.40 Å). With R = Pr, Pt4Sn6Pr3-x (oP52, Pnma, a = 7.2863(3) Å, b = 4.4909(2) Å, c = 35.114(1) Å) is also obtained, which might be considered a high-temperature polymorph with disorder on the Sn- and Pr-sites. For R = Nd and Sm, a structurally related isostructural series with a slightly different composition Pt3Sn5R2-x (oP52, Cmc21, a = 4.50-4.51 Å, b = 26.14-26.30 Å, c ≈ 7.29 Å) has been observed, together with Pt7Sn9Sm5 (oS42, Amm2, a = 4.3289(5) Å, b = 28.798(4) Å, c = 7.2534(9) Å) under the same conditions. The latter exhibits the rare Zr5Pd9P7-type structure, linking polar intermetallics to metal phosphides, in accord with P7Pd9Zr5≡Pt7Sn9Sm5. All structures may be described in terms of either negative Pt/Sn networks encapsulating positive R atoms, or {PtSnx} clusters (x = 5, 6, or rarely 7) sharing vertices and edges with R in the second coordination sphere and with considerable heterometallic Pt-R bonding contributions.

Although rare-earth-metal-transition-metal (R/T) phase diagrams have been explored extensively, our recent studies have uncovered new previously nonexistent binary intermetallics. These compounds belong to a narrow region between 70 and 71.4 atom % of the rare-earth metal but represent four different structure types. The binaries Tb7Pd3 and Er17Pd7 are compositionally approaching (less than 1 atom % difference) the previously reported R2.16Pd0.89 (R = Tb and Er), and apparently form by peritectoid transformation, thus, being hard to detect by fast cooling. Tb7Pd3 (1) crystallizes in the Th7Fe3 structure type (hP20, P63mc, a = 9.8846(4) Å, c = 6.2316(3) Å, Z = 2) while Er17Pd7 (2) belongs to the Pr17Co7 type being its second reported representative (cP96, P213, a = 13.365(2) Å, Z = 4). Er17Pd7 (2) is overlapping with the cubic F-centered Er2.11Pd0.89 (3b, Fd3̅m, a = 13.361(1) Å, Z = 32) with practically identical unit cell parameters but a significantly different structure. Electronic structure calculations confirm that heteroatomic R-T bonding strongly dominates in all structures; T-T bonding interactions are individually strong but do not play a significant role in the total bonding.

Isonicotine amide, picoline amide, pyrazine 2-amide, 2- and 4-amino benzamides and various CuII salts were used to target CuII complexes of these ligands alongside with 1D and 2D coordination polymers. Under the criterion of obtaining crystalline and single phased materials a number of new compounds were reliably reproduced. Remarkably, for some of these compounds the ideal Cu:ligand ratio of the starting materials turned out to be very different from Cu:ligand ratio in the products. Crystal and molecular structures from single-crystal XRD were obtained for all new compounds; phase purity was checked using powder XRD. We observed exclusively the Oamide and not the NH2amide function binding to CuII. In most of the cases; this occurred in chelates with the second pyridine, pyrazine or aminophenyl N function. µ-O,N ditopic bridging was frequently observed for the N = pyridine, pyrazine or aminophenyl functions, but not exclusively. The geometry around CuII in these compounds was very often axially elongated octahedral or square pyramidal. X-band EPR spectra of powder samples revealed various spectral symmetry patterns ranging from axial over rhombic to inverse axial. Although the EPR spectra cannot be unequivocally correlated to the observed geometry of CuII in the solid state structures, the EPR patterns can help to support assumed structures as shown for the compound [Cu(Ina)2Br2] (Ina = isonicotine amide). As UV-vis absorption spectroscopy and magnetic measurement in the solid can also be roughly correlated to the surrounding of CuII, we suggest the combination of EPR, UV-vis spectroscopy and magnetic measurements to elucidate possible structures of CuII compounds with such ligands.

An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The rare-earth elements in the divalent state, i.e. with oxidation number + 2, may either have the electron configuration 4f(n+1)5d degrees(symbolized as R2+) or 4f(n)5d(1) (R(3+)e(-)). As R2+ (R = Eu, Yb, Sm, Tm, Dy, Nd) they can either be contained in extended solids as in the insulating diiodides RI2, or in coordination complexes such as samarocene, Kagan's reagent, or TmI2(DME)(3). In the case of R(3+)e(-), the "excess" d electron can either be delocalized and cause (semi)metallic behavior in extended solids, e.g. in LaI2, or localized with the R(3+)e(-) = 4f(n)5d(1) ion trapped in a coordination complex with (super)bulky ligands such as in [K(2.2.2-crypt)][LaCp ''(3)]. Thus, the seemingly small cause of a one-electron configuration crossover, 4f(n+1)5d degrees <--> Hf(n)5d(1) has a large effect on the chemical behavior and physical properties of the respective compounds where atomic properties and ligand effects play important roles.

Although the Pt-Pr phase diagram has been explored well, recent work on rare-earth metal cluster halides with endohedral transition metal atoms has provided a new binary intermetallic that is nonexistent in the known phase diagram: The binary Pt3Pr4 (1) crystallizes in a new structure type ( mP56, P21/ c, a = 12.353(2) Å, b = 7.4837(9) Å, c = 17.279(2) Å, β = 118.003(7)°, Z = 8) with six crystallographically independent Pt as well as eight Pr positions. The subsequent detailed investigation has led to another previously unreported, binary phase with the Ga2Gd3 structure type, Pt2- xPr3 (2, tI80, I4/ mcm, a = 11.931(9) Å, c = 14.45(1) Å, Z = 16), that is practically overlapping with the rhombohedral Pt2Pr3 existing in the phase diagram. Application of different tin containing fluxes to reproduce the newly detected phases brought about two almost iso-compositional ternary compounds with Sn, Pt4Sn6Pr2.91 (3), and Pt4Sn6Pr3 (4), as well as Pt12Sn24Pr4.84 (5). 3 is a representative of the Pt4Ge6Ce3 type ( oP52, Pnma, a = 7.2863(3) Å, b = 4.4909(2) Å, c = 35.114(2) Å), while 4 represents a new variant of the prolific T4 E6 R3 family ( T = transition metal, E = main group (semi)metal, R = rare-earth metal; Pt4Sn6Pr3: oP52, Pnma, a = 27.623(1) Å, b = 4.5958(2) Å, c = 9.3499(5) Å). Pt12Sn24Pr5- x (5) crystallizes as a variant of the Ni8Sn16Gd3 type ( cI82, Im3̅, a = 12.274(1) Å, Z = 2). Electronic structure calculations provide hints on the origin of the structural changes ( pseudo-polymorphism) for Pt xPr3 with x = 1.97 and 2.00, respectively, and reveal that heteroatomic Pt-Pr bonding strongly dominates in both binaries while the addition of the reactive metal tin leads to dominating Pt-Sn bonding interactions in the ternaries; Pt-Pt bonding interactions are strong but represent a minority in the binaries and are not present at all in the ternaries.

An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

New organometallic complexes [M(dppe)(R)(2)] {where M = Pt or Pd, dppe = 1,2-bis(diphenylphosphano) ethane, and R = C6F4H-x (x = 6,5,4), C6F3H2-3,5, C6F3H2-5,6, C6F3H2-3,6, C6F4(OMe)-4, and C6F4(cyclo-C5H10N)-4, the numbers x refer to the positions of the protons in the polyfluoroaryl ligands} were synthesised either through transmetalation from the dichlorido complexes [M(dppe)Cl-2] or through ligand exchange using [M(diene)Cl-2] precursor complexes with diene = 1,5-cyclooctadiene (cod) or 1,5-hexadiene (hex). Alternatively, [M(dppX)Cl(R)] complexes with dppX = dppm (1,1-bis(diphenylphosphano) methane), dppe, dppp (1,3-bis(diphenylphosphano) propane), and dppb (1,4-bis(diphenylphosphano) butane) were prepared in decarboxylation reactions from thallium(I) carboxylates Tl(O2CR). The different preparative methods were compared in terms of yield and purity. Structural and spectroscopic data are reported for the new dppX- and diene-M(R)(2) complexes. Antiproliferative activity was investigated for these new complexes against the HT-29 (colon carcinoma) and MCF-7 (breast adenocarcinoma) cell lines, and the active compounds of this first series together with organometallic dppX or hex Pt-II or Pd-II complexes were then included in cell tests using L1210 (leukaemia cells) and the cisplatin-resistant L1210/DDP cell line. Remarkably, promising antiproliferative results were found for a few Pt-II and Pd-II complexes, while structurally closely related compounds were essentially nontoxic.

Four compounds are reported in this study. Co7Pr17 (10, cP96, P2(1)3, a = 13.4147(8) angstrom, Z = 4), either nonexistent or obscured in the Co/Pr phase diagram, has been obtained from a PrBr3 flux. With 29.2 mol % Co, it is close to Co2Pr5 (28.6 mol % Co, 2, C2Mn5 type of structure, mC28, C2/c, a = 16.5471(7) angstrom, b = 6.5107(3) angstrom, c = 7.1067(3) angstrom, beta = 96.230(3)degrees, Z = 4), existent in the Co/Pr phase diagram, produced by arc-melting of a stoichiometric mixture of the metals. The addition of the reactive metal tin to Co/Pr mixtures yielded two new ternary polar intermetallics, CoSn3Pr1-x (x = 0.04, 11, RuSn3La type, cP40, Pm(3) over barn, a = 9.587(3) angstrom, Z = 8) and Co2-xSn7Pr3 (x = 0.78, 12, Ni2-xSn7-yCe3 type, oC24, Cmmm, a = 4.5043(4) angstrom, b = 27.227(2) angstrom, c = 4.5444(3) angstrom, Z = 2). Electronic structure calculations reveal extensive heteroatomic Co-Pr interactions in the binaries with little homoatomic contributions. With tin as the third component in the ternaries, heteroatomic Co-Sn and Sn-Pr bonding interactions are dominant, following the sequence of coordination spheres around Co.

The three binary Tb/Er-rich transition metal compounds Tb3Pd2 (triterbium dipalladium), Er3Pd2 (trierbium dipalladium) and Er6Co5-x (hexaerbium pentacobalt) crystallize in the space groups Pbam (Pearson symbol oP20), P4/mbm (tP10) and P63/m (hP22), respectively. Single crystals of Tb3Pd2 and Er6Co5-x suitable for X-ray structure analysis were obtained using rare-earth halides as a flux. Tb3Pd2 adopts its own structure type, which can be described as a superstructural derivative of the U3Si2 type, which is the type adopted by Er3Pd2. Compound Er6Co5-x belongs to the Ce6Co2-xSi3 family. All three compounds feature fused tricapped {TR6} (R = rare-earth metal and T = transition metal) trigonal prismatic heterometallic clusters. R3Pd2 is reported to crystallize in the U3Si2 type; however, our more detailed structure analysis reveals that deviations occur with heavier R elements. Similarly, Er6Co5-x was assumed to be stoichiometric Er4Co3 = Er6Co4.5. Our studies reveal that it has a single defective transition-metal site leading to the composition Er6Co4.72(2). LMTO (linear muffin-tin orbital)-based electronic structure calculations suggest the strong domination of heteroatomic bonding in all three structures.

Herein, we report a hybrid polyoxometalate organic-inorganic compound, Na-2[(HGMP)(2)Mo5O15]center dot 7H(2)O (1; where GMP=guanosine monophosphate), which spontaneously assembles into a structure with dimensions that are strikingly similar to those of the naturally occurring left-handed Z-form of DNA. The helical parameters in the crystal structure of the new compound, such as rise per turn and helical twist per dimer, are nearly identical to this DNA conformation, allowing a close comparison of the two structures. Solution circular dichroism studies show that compound 1 also forms extended secondary structures in solution. Gel electrophoresis studies demonstrate the formation of non-covalent adducts with natural plasmids. Thus we show a route by which simple hybrid inorganic-organic monomers, such as compound 1, can spontaneously assemble into a double helix without the need for a covalently connected linear sequence of nucleic acid base pairs.

The design of new materials with desired chemical and physical characteristics requires thorough understanding of the underlying composition-structure-property relationships and the experimental possibility of their modification through the controlled involvement of new components. From this point of view, intermetallic phases, a class of compounds formed by two or more metals, present an endless field of combinations that produce several chemical compound classes ranging from simple alloys to true ionic compounds. Polar intermetallics (PICs) belong to the class that is electronically situated in the middle, between Hume-Rothery phases and Zintl compounds and possessing e/a (valence electron per atom) values around 2. In contrast to the latter, where logical rules of formation and classification systems were developed decades ago, polar intermetallics remain a dark horse with a huge diversity of crystal structures but unclear mechanisms of their formation. Partial incorporation of structural and bonding features from both nonpolar and Zintl compounds is commonly observed here. A decent number of PICs can be described in terms of complex metallic alloys (CMAs) following the Hume-Rothery electron-counting schemes but exhibit electronic structure changes that cannot be explained by the latter. Our research is aimed at the discovery and synthesis of new polar intermetallic compounds, their structural characterization, and investigation of their properties in line with the analysis of the principles connecting all of these components. Understanding of the basic structural tendencies is one of the most anticipated outcomes of this analysis, and systematization of the available knowledge is the initial and most important step. In this Account, we focus on a well-represented but rather small section of PICs: ternary intermetallic compounds of gold with electropositive and post-transition metals of groups 12 to 15. The strong influence of relativistic effects in its chemical bonding results in special, frequently unique structural motifs, while at the same time gold participates in common structure types as an ordinary transition element. Enhanced bonding strength leads to the formation and stabilization of complex homo- and heteroatomic clusters and networks that are compositionally restricted to just a few options throughout the periodic table. Because it has the highest absolute electronegativity among metals, comparable to those of some halogens, gold usually plays the role of an anion, even being able to form true salts with the most electropositive metals. We discuss the occurrence of the structure types and show the place of gold intermetallics in the general picture. Among the structures considered are ones as common as AlB2 or BaAl4 types, in line with the recently discovered diamond-like homoatomic metal networks, formation of local fivefold symmetry, different types of tunneled structures, and more complex intergrown multicomponent structures.

AbstractWir berichten hier über ein hybrides organisch‐anorganisches Polyoxometallat, Na2[(HGMP)2Mo5O15]⋅7 H2O (1) (mit GMP=Guanosinmonophosphat), das sich spontan zu einer Struktur zusammenfügt, deren Dimensionen jenen der natürlich vorkommenden linkshändigen Z‐Form der DNA verblüffend ähnlich sind. Die Helixparameter in der Kristallstruktur dieser neuen Verbindung, wie Anstieg pro Windung und helikale Verdrillung pro Dimer, sind nahezu identisch zur DNA, was einen eingehenden Vergleich von beiden Strukturen erlaubt. Zirkulardichroismus (CD) in Lösung zeigt, dass Verbindung 1 auch in Lösung ausgedehnte Sekundärstrukturen aufweist. Gelelektrophorese‐Untersuchungen weisen die Bildung nichtkovalenter Addukte mit natürlichen Plasmiden nach. Damit können wir einen Weg aufzeigen, auf dem einfache, hybride organisch‐anorganische Monomere, wie in Verbindung 1, sich spontan zu einer Doppelhelix zusammenlagern können, ohne dass dazu eine kovalent gebundene lineare Sequenz von Nuklein‐Säure‐Base‐Paaren nötig wäre.

Reaction of various sulphur ligands L (SEt−, SPh−, SC6F4H-4−, SEt2, StBu2, SnBu2, DMSO, DPSO) with the precursors [(COD)M(R)Cl] (COD=1,5-cyclooctadiene, M=Pd or Pt; R=methyl (Me) or benzyl (Bn); DMSO=dimethyl sulfoxide; DPSO=diphenyl sulfoxide) allowed isolation and characterisation of mononuclear neutral (n=0) or cationic (n=1) complexes [(COD)Pt(R)(L)]n+. Reaction of l-cysteine (HCys) with [(COD)Pt(Me)Cl] under similar conditions gave the binuclear cationic complex in [{(COD)Pt(Me)}2(μ-Cys)]Cl. Detailed NMR spectroscopy and single crystal X-ray diffraction in the case of [(COD)Pt(Me)(SEt2)][SbF6] and [(COD)Pt(Me)(DMSO)][SbF6] reveal markedly labilised Pt–S bonds as a consequence of the highly covalent Pt–C bonds of the R coligands in these organometallic species. Cationic charge (n=1) seems to lower the Pt–S bond strength further. Consequently, most of these complexes are not stable long-term in aqueous DMF (N,N-dimethylformamide) solutions. This made the evaluation of their antiproliferative properties towards HT-29 colon carcinoma and MCF-7 breast adenocarcinoma cell lines impossible. Only the two complexes [(COD)Pt(R)(SC6F4H-4)] with R=Me or SC6F4H-4 coligands could be tested with the R=Me complex showing promising activity (in the range of cisplatin), while the R=SC6F4H-4 derivative is largely inactive, as were the phosphane complexes [(dppe)Pt(SC6F4H-4)2] (dppe=1,2-bis(diphenylphosphino)ethane), cis-[(PPh3)2Pt(SC6F4H-4)2] and cis-[(PPh3)2PtCl2] which were tested for comparison. In turn, our findings might pave the way to new Pt anti-cancer drugs with largely reduced unwanted depletion of incorporated drugs and reduced side-effects from binding to S-containing biomolecules.