Synthesis and structure of three clusters (μ-H)Os3 [μ-1,1,4-η2-XCH2CH(CO2CH2CH3)NH2](CO)9 (X = S,O)

Institute of Inorganic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 31, No. 6, pp. 108–116, November–December, 1990.     

Structures of large transition metal clusters

The present review surveys the results of X-ray diffraction studies of large stoichiometric transition metal clusters containing from 20 to 145 atoms in metal cores surrounded by ligand shells (72 compounds). Structures of such clusters have fragments of close packings (face-centered cubic (f.c.c.), hexagonal close (h.c.p.), and body-centered cubic (b.c.c.) packings) characteristic of crystalline bulk metals as well as mixed packings (f.c.c./h.c.p.), local close packings with pentagonal symmetry, and strongly distorted amorphous packings. The observed packing types, their distortions, and the relationship between the atomic structures of metal cores and the atomic radial distribution functions (RDF) are discussed. The structural principles established for the large clusters are applied to analysis of the experimental RDF for metal nanoparticles determined by X-ray diffraction and EXAFS spectroscopy.     

Structured polyphenylenes as carriers of palladium nanoparticles used as selective hydrogenation catalysts

Structured polyphenylenes that are used as matrices for immobilization of palladium nanoparticles are synthesized through the cyclocondensation of acetylaromatic compounds followed by structuring at different temperatures and, as a result, different crosslink densities. The relationship between the structure and structuring temperature of the polymers is investigated. It is shown that the sizes of palladium nanoparticles immobilized in polyphenylene matrices depend on the conditions of polymer structuring. The resulting catalytic systems are examined for the selective hydrogenation of triple bonds in acetylene alcohols.     

Application of molecular mechanics method to structural calculations of π-complexes of transition metals

A. N. Nesmeyanov Institute of Heteroorganic Compounds. Translated from zhurnal Strukturnoi Khimii, Vol. 28, No. 4, pp. 3–13, July–August, 1987.     

Synthesis and structure of polynuclear carbonylphosphine clusters of palladium

Reductive condensation of Pd(OAc)₂ in dioxane in the presence of CO and PR₃ (R = Et, Buⁿ) with addition of CF₃COOH leads to the formation of decanuclear Pd₁₀(μ₃-CO)₄(μ₂-CO)₈(PBuⁿ₃)₆ (I) and Pd₁₀(CO)₁₄(PBuⁿ₃) (II) at Pd(OAc)₂:PR₃ molar ratios of 1:4–1:10 and 1:1.5–1:2.5, respectively. The use of CH₃COOH instead of CF₃COOH results in tetranuclear clusters Pd₄(CO)₅(PR₃)₄ (III) and Pd₄(μ₂-CO)₆(PBuⁿ₃) (IV). I ? III and III → IV transformations occur in organic media. The structures of I (space group P2₁/n, Z = λMo, 12125 independent reflections, R = 0.047) and IV (Pz:3, Z = λMo, 3254 reflections, R = 0.098) were established by X-Ray diffractions analysis. Cluster I is a 10-vertex Pd₁₀ polyhedron, an octahedron with four unsymmetrically centered non-adjacent faces. The average PdPd distances in the octahedron are 2.825 Å, in the eight short Pd_oct.Pd_cap. bonds with the “equatorial” Pd atoms of the inner octahedron, bridged by the μ₂-CO ligands, are 2.709 Å, and in the four elongated (without bridging CO groups) bonds with the apical Pd atoms of the octahedron are 3.300–3.422 Å. The PBuⁿ₃ ligands are coordinated to the apical Pd atoms and the capping atoms (PdP 2.291–2.324 Å). Cluster IV is tetrahedral, with the CO ligands symmetrically bridged; PdPd 2.778–2.817; PdP 2.232–2.291; PdC 2.06 Å (average).     

New molecular complexes of fullerenes C60 and C70 with tetraphenylporphyrins [M(tpp)], in which M=H2, Mn, Co, Cu, Zn, and FeCl

New molecular complexes of fullerenes C60 and C70 with tetraphenylporphyrins [M(tpp)] in which M-H2, MnII, CoII, CuII, ZnII and Fe(III)Cl, have been synthesised. Crystal structures of two C60 complexes with H2TPP, which differ only in the number of benzene solvated molecules, and C60 and C70 complexes with [Cu(tpp)] have been studied. The fullerene molecules form a honeycomb motif in H2TPP.2C60. 3C6H6, puckered graphite-like layers in H2TPP.2C60.4C6H6, zigzag chains in [Cu(tpp)].C70.1.5C7H8.0.5C2HCl3 and columns in [Cu(tpp)]2.C60. H2TPP has van der Waals contacts with C60 through nitrogen atoms and phenyl groups. Copper atoms of the [Cu(tpp)] molecules are weakly coordinated with C70, but form no shortened contacts with C60. The formation of molecular complexes with fullerenes affects the ESR spectra of [M(tpp)] (M = Mn, Co and Cu). [Mn(tpp)] in the complex with C70 lowers its spin state from S = 5/2 to S = 1/2, whereas [Co(tpp)] and [Cu(tpp)] change the constants of hyperfine interaction. ESR, IR, UV-visible and X-ray photoelectron spectroscopic data show no noticeable charge transfer from the porphyrinate to the fullerene molecules.     

Syntheses of organogold(1+) compounds by direct auration

Organogold(1+) compounds have been synthesized by direct auration of cyclopentadiene, cyanoacetic ester and malonitrile with (Ph₃PAu)₃O⁺BF₄^?. An X-ray structural study (λ Mo, 5062 reflections, R = 0.039) of bis(triphenylphosphinegold)malonitrile has been carried out (monoclinic, a = 12.055(6), b = 14.086(5), c = 20.466(12) Å, β = 90.32(4)°, space group P2₁/c, Z = 4). The AuAu bond length is 2.912(1) Å.     

An EXAFS study of the molecular structure of heterometallic chalcogenide clusters

Applicability of EXAFS spectroscopy for determination of the molecular structure of heterometallic chalcogenide clusters in the crystalline state and in solution was examined. The spatial structure of the metal core of the FeMoW(μ₃-Se)(CO)₇(η⁵-C₅H₅) cluster was determined using EXAFS data obtained at the K absorption edge for Fe, Mo, and Se and at the L_III-edge for W. The geometric parameters (the bond lengths and bond angles) obtained from EXAFS data are close to those determined by X-ray analysis. The Mo K-edge EXAFS study of the structurally similar FeMo₂Te(CO)₇(η⁵-C₅H₅) cluster both in the crystalline state and ino-xylene solution confirmed that the geometry of the metal core of the cluster is retained in solution. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1395–1398, August, 2000.