Synthesis and characterisation of high-nuclearity osmium-silver mixed-metal clusters

The reaction of the triosmium cluster anion, [Os(3)(micro-H)(CO)(11)][PPN] (PPN = [N(PPh(3))2]+), with [AgPF(6)] in the presence of [Ir(PPh(3))2(CO)Cl] in THF at room temperature affords two new high-nuclearity osmium-silver clusters, [Os(13)Ag(9)(CO)48][PPN] (1) and [Os(9)Ag(9)(micro3-O)2(CO)30][PPN] (2), and an iridium complex, [Ir(PPh(3))2(CO)Cl(O(2))] (3).     

Synthesis and characterisation of linked triosmium clusters using the bis(diphenylphosphino)acetylene ligand

The reaction of Os₃(CO)₁₁(NCMe) with bis(diphenylphosphino)acetylene (dppa) at room temperature affords [Os₃(CO)₁₁]₂(dppa) (1) in good yield, while Os₃(CO)₁₀(NCMe)₂ with an excess of dppa gives [Os₃(CO)₁₀(dppa)]₃ (2) and [Os₃(CO)₁₀(dppa)]₄ (3) in moderate yields. The structure of 1 has been determined by a single crystal X-ray diffraction study.     

Structure and properties of iron oxide clusters: From Fe6 to Fe6O20 and from Fe7 to Fe7O24

Geometrical and electronic structures of the neutral and singly negatively charged Fe₆O_n and Fe₇O_m clusters in the range of 1 ≤ n ≤ 20 and 1 ≤ m ≤ 24, respectively, are computed using density functional theory with the generalized gradient approximation. The largest clusters in the two series, Fe₆O₂₀ and Fe₇O₂₄, can be described as Fe(FeO₄)₅ and Fe(FeO₄)₆ or alternatively as [FeO₅](FeO₃)₅ and [FeO₆](FeO₃)₆, respectively. The Fe₆O₂₀ and Fe₇O₂₄ clusters possess adiabatic electron affinities (EA_ad) of 5.64 eV and 5.80 eV and can be attributed to the class of hyperhalogens since FeO₄ is an unique closed‐shell superhalogen with the EA_ad of 3.9 eV. The spin character of the lowest total energy states in both series changes from ferromagnetic to ferrimagnetic or antiferromagnetic when the first Fe? O? Fe bridge is formed. Oxidation decreases substantially the polarizability per atom of the initial bare clusters; namely, from 5.98 ų of Fe₆ to 2.47 ų of Fe₆O₂₀ and from 5.67 ų of Fe₇ to 2.38 ų of Fe₇O₂₄. The results of our computations pertaining to the binding energies of O, Fe, O₂, and FeO in the Fe₇O_m series provide an explanation for the experimentally observed abundance of the iron oxide nanoparticles with stoichiometric compositions. © 2016 Wiley Periodicals, Inc.     

Synthesis and magnetic properties of heptadecametallic Fe(III) clusters

Heptadecametallic, all-ferric pieces of molecular magnetite of general formula HL_x[Fe₁₇O₁₆(OH)₁₂(L)₁₂Br₄]Br_3+x (L = β-picoline, isoquinoline, 3,5-lutidine; x = 0, 1) are made by the simple dissolution of FeBr₃ in L. The β-picoline (or equivalent) molecules act simultaneously as solvent, base and capping ligand. The resultant structure consists of a metal–oxygen core containing both octahedral and tetrahedral Fe(III) ions that is the exact analogue of the metal–oxygen positions seen in the magnetite lattice. Antiferromagnetic exchange between the tetrahedral and octahedral Fe(III) ions lead to the stabilization of an S = 35/2 spin ground state.     

Synthesis and magnetic properties of wheel-shaped [Mn12] and [Fe6] complexes

The reactions of the ligands N-methyldiethanol amine and N-ethyldiethanol amine (abbreviated H(2)mdea and H(2)edea, respectively) with [Mn(12)O(12)(O(2)CCH(3))(16)(H(2)O)(4)] yield novel dodecanuclear wheel-shaped products. The capability of the ligands H(2)mdea and H(2)edea to support wheel structures in metals other than Mn is demonstrated with the crystal structure of a new hexanuclear ferric wheel.     

Syntheses,structures and magnetic properties of Fe6 and Fe12 ferric wheels

Starting from the same Fe3O(RCO2)6 complex and using a similar synthesis strategy, the Fe6 and Fe12 wheels were obtained by utilizing two designed ligands, 2-amino-2-methyl-1,3-propanediol(L1) and 1,3-propanediol(L2), respectively. A biological buffer reagent, Bis-Tris(2-[bis-(2-hydroxyethyl)amino]-2-(hydroxymethyl)propane-1,3-diol) was first introduced in the synthesis of the Fe12 wheel, playing a vital role in adjusting the acidity of reaction environment. Magnetic studies on both Fe6 and Fe12 wheels revealed strong antiferromagnetic coupling between the spins on FeIII ions.     

Synthesis, characterisation and redox behaviour of isocyanide incorporated, chalcogen stabilised mixed-metal clusters

Room temperature reaction of a benzene solution of [Cp₂Mo₂Fe₂(CO)₇(μ₃-E)(μ₃-E^′)] (EE^′=Se₂ (1), STe (2), SeTe (3)) with PrⁱNC or Bu^tNC resulted in the formation of iron bonded isocyanide clusters [Cp₂Mo₂Fe₂(RNC)(CO)₆ (μ₃-E)(μ₃-E^′)], [E=E^′=Se, R=Prⁱ (5) or Bu^t (9); E=S, E^′=Te, R=Prⁱ (6a, 6b) or R=Bu^t (10a, 10b); E=Se, E^′=Te, R=Prⁱ (7a, 7b) or R=Bu^t (11a, 11b)] and molybdenum bonded isocyanide clusters [Cp₂(RNC)Mo₂Fe₂(CO)₆(μ₃-E)(μ₃-E^′)], [E=E^′=Se, R=Prⁱ(13) or Bu^t (17); E=S, E^′=Te, R=Prⁱ (14) or R=Bu^t, (18); E=Se, E^′=Te, R=Prⁱ (15) or R=Bu^t (19)]. Two isomers (a and b) were detected by ¹H NMR spectroscopy for the mixed-chalcogen clusters 6, 7, 10 and 11, where the isocyanide group is bonded to an iron atom. Thermolytic reaction conditions were necessary for the reaction of [(η⁵-C₅H₅)₂Mo₂Fe₂(CO)₇(μ₃-Te)₂] (4) with Prⁱ NC or Bu^t NC to give [Cp₂Mo₂Fe₂(RNC)(CO)₆(μ₃-Te)₂] (R=Prⁱ (8) or R=Bu^t, (12)) and [Cp₂(RNC)Mo₂Fe₂(CO)₆(μ₃-Te)₂] (R=Prⁱ (8)). Compounds 5-19 have been characterised by IR and ¹H and ¹³C NMR spectroscopy. The Se- and Te-bridged compounds have been further characterised by ⁷⁷Se and ¹²⁵Te NMR spectroscopy. The structures of compounds 12 and 14 were determined by single crystal X-ray diffraction methods. Redox properties of the mixed-metal clusters, 2, 6, 8, 12 and 14 have been studied by cyclic voltammetry in the potential range ±2.5 V at 298 K, using a platinum working electrode.     

Synthesis and characterisation of saturated and unsaturated triruthenium clusters containing electronically symmetrical and asymmetrical alkynes

The synthesis and characterisation of μ₃-η²-alkynyl triruthenium clusters, [Ru₃(μ₃-η²-R¹-4-C₆H₄CCR²)(μ-dppm)(μ-CO)(CO)₇] (1, saturated), [Ru₃(μ₃-η²-R¹-4-C₆H₄CCR²)(μ-dppm)(CO)₇] (2, unsaturated) and [Ru₃(μ₃-η²-R¹-4-C₆H₄CCR²)(μ-dppm)(PPh₃)(CO)₇] (3, saturated) containing symmetrical and asymmetrical alkynes in which R¹ and R² are electron donor or electron withdrawing groups in the para position of the aromatic ring(s) or R² is ferrocenyl, are reported. Clusters 1 were obtained from the reactions of [PPN][Ru₃(μ-Cl)(CO)₁₀] with R¹-4-C₆H₄CCR² and dppm. Clusters 1 were successfully decarbonylated to give unsturated clusters 2, with the exception of the FcCCC₆H₄-4-NO₂ containing cluster, which is stable. Novel adducts 3 were obtained in high yields by addition of PPh₃ to unsaturated clusters 2. Clusters 1-3 were characterised by analytical and spectroscopic data, and structures were proposed on the basis of systematic ³¹P NMR studies and correlations with X-ray structural data of related compounds available in the literature. Saturated compounds 1 contain a CO and a dppm ligands bridging the same edge, which is also parallel to the μ₃-η²-alkyne, as opposed to the structure previously proposed for the PhCCPh and other derivatives, and established by X-ray crystallography for the PhCCCCPh cluster derivative, in which the dppm ligand bridges a different edge. Unsaturated compounds 2 exhibit the same structure established for the PhCCPh derivative in the solid state, with the alkyne bonded in the μ₃-η²-mode perpendicular to the Ru₂ edge supported by the dppm ligand. Because the dppm phosphorus chemical shifts were sensitive to the alkyne electronic asymmetry, it was possible to show that clusters containing electronically asymmetrical alkynes exist in two inseparable isomeric forms, which differ with respect to the alkyne orientation. Similarly to their osmium analogues, saturated compounds 3 exist as inseparable mixtures of isomers that differ with respect to the position of the bridging CO and dppm ligands, and in the cases of asymmetrical alkyne derivatives, also with respect to the orientation of the alkyne. This work has established, therefore, that μ-CO and dppm ligand positions respective to the μ₃-η²-alkyne in saturated clusters 1 and 3 are sensitive both to the nature of the coordinated alkyne and to the presence of a PPh₃ in place of a CO ligand on the metal frame.     

Synthesis and characterisation of a mixed-valence Mn13 complex with S6 symmetry by using 2-phenoxybenzoate

The synthesis, structure and magnetic properties of [Mn(13)O(8)(OEt)6(O(2)CC(6)H(4)OPh)12] are reported as the first example of a high nuclearity manganese complex with 2-phenoxybenzoate: the complex possesses S6 symmetry and an S = 11/2 ground state.     

Synthesis and characterization of hydrogen-bonded assemblies of W6S8L6 clusters

Ligand-exchange reactions involving octahedral W6S8 clusters and a family of pyridine-based ligands (isonicotinic acid, isonicotinamide, 4-hydroxypyridine, 4-aminopyridine, 4-pyridineacetamide) have been explored with the goal of preparing compounds that crystallize in hydrogen-bonded arrays. Two new compounds, W6S8(4-pyridineacetamide)6.DMF.4-pyridineacetamide (1) and W6S8(4-aminopyridine)6.4DMF (2), were isolated and characterized by single-crystal X-ray diffraction. Both compounds crystallize in the P2(1)/c space group with a = 16.461(1), b = 33.08(2), c = 13.165(10) A, beta = 103.270(15) degrees for 1 and a = 13.8988(5), b = 13.2791(5), c = 15.6293(6) A, beta = 108.5410(10) degrees for 2. Each compound was further characterized by 1H NMR spectroscopy, elemental (CHN) analysis, and thermogravimetric analysis. Examination of the structures shows that 1 forms a three-dimensional hydrogen-bonded network in which each 4-pyridineacetamide ligand interacts with ligands on neighboring clusters or with the free ligand of crystallization. This is the first hydrogen-bonded network formed from W6S8 clusters. In 2, the amino groups act as hydrogen-bond donors toward DMF molecules of crystallization, but an extended array is not formed. In addition, the binding strengths of these pyridine-based ligands to the W6S8 cluster were studied through quantitative 1H NMR studies of ligand-exchange reactions. A qualitative relationship was found between ligand binding strengths and Hammett substituent constants for this group of ligands.     

Synthesis of Ge2NiS4 clusters and the thermal transformation to a Ge4Ni6S12 cluster

The reaction of Ni(dppe)Cl2 and syn-[DmpGe(SLi)(mu-S)2Ge(SLi)Dmp] prepared in situ from syn-[DmpGe(SH)(mu-S)2Ge(SH)Dmp] (1) and n-BuLi (2 equiv) afforded the Ge2NiS4 cluster, [DmpGe(mu-S)]2(mu-S)2Ni(dppe) (2) (Dmp = 2,6-dimesitylphenyl). The nickel in 2 assumes a slightly distorted square planar geometry. However, another Ge2NiS4 cluster, [DmpGe(mu-S)]2(mu-S)2Ni(PPh3)2 (3) obtained from a similar reaction with Ni(PPh3)2Cl2, contains the nickel in a tetrahedron. When 3 was heated to 120 degrees C in toluene, a novel Ge4Ni6S12 cluster [DmpGe(mu-S)3]4Ni6 (5) was obtained. In cluster 5, six nickels form an octahedron with the nickels occupying its vertexes, and four DmpGeS3 units cap half of the trigonal faces.     

Synthesis and characterisation of phosphane-substituted Co3C clusters having a pendant allyl side-chain

Substituted μ₃-carbido-capped tricobalt carbonyl clusters have been synthesised by reaction of [Co₃(μ₃-C(O)OCH₂CHCH₂)(CO)₉] with a range of monodentate and chelating phosphane ligands. The products have been characterised by microanalysis, IR and NMR spectroscopy, mass spectrometry and, in the case of [Co₃(μ₃-CR)(CO)₇(dppe)], [Co₃(μ₃-CR)(CO)₇(dppm)], [Co₃(μ₃-CR)(CO)₇(PPh₃)₂], [Co₃(μ₃-CR)(CO)₇(PMe₃)₂] and [Co₃(μ₃-CR)(CO)₆(PEt₃)₃] (R=C(O)OCH₂CHCH₂), single crystal X-ray diffraction.     

钼铁硫原子簇化合物的合成与结构化学研究II: 以Fe(SR)6为桥的双类立方烷化合物的合成及(Et4N)4[Mo2Fe7S8(SC6H4CH3-m)12].2THF的晶体结构

在乙腈溶液中(Et4N)2[Fe4(SR)10]与(Et4N)2[MoS4]反应半小时生成对氧极为敏感的系列黑色晶状化合物(Et4N)4[Mo2Fe7S8(SR)12](R=C6H5,1;R=C6H4CH3-m, 2;R=C6H4CH3-o, 3;R=C6H4CH3-ρ,4). 2.2THF晶体的分子量为2982.8, 属单斜晶系;空间群为P21/n; a=18.022(2), b=18.375(2), c=22.254(3)A; β=71.04(1)°;V=6969(2)A^3;Dc=1.424g.cm^-^3;Z=2;F(000)=3108.晶体结构用直接法解出,修正至R=0.064. 2.2THF中Mo...Mo'距离为7.234A.     

Large spin differences in structurally related Fe6 molecular clusters and their magnetostructural explanation

The syntheses, crystal structures, and magnetic characterizations of three new hexanuclear iron(III) compounds are reported. Known [Fe(6)O(2)(OH)(2)(O(2)CBu(t))(10)(hep)(2)] (1) is converted to new [Fe(6)O(2)(OH)(O(2)CBu(t))(9)(hep)(4)] (3) when treated with an excess of 2-(2-hydroxyethyl)-pyridine (hepH). Similarly, the new compound [Fe(6)O(2)(OH)(2)(O(2)CPh)(10)(hep)(2)] (2), obtained from the reaction of [Fe(3)O(O(2)CPh)(6)(H(2)O)(3)] with hepH, is converted to [Fe(6)O(2)(OH)(O(2)CPh)(9)(hep)(4)] (4) when treated with an excess of hepH. This can be reversed by recrystallization from MeCN. The cores of the four Fe(6) complexes all comprise two triangular [Fe(3)(mu(3)-O)(O(2)CR)(3)(hep)](+3) units connected at two of their apices by two sets of bridging ligands. However, 1 and 2 differ slightly from 3 and 4 in the precise way the two Fe(3) units are linked together. In 1 and 2, the two sets of bridging ligands are identical, consisting of one mu-hydroxo and two mu-carboxylate groups bridging each Fe(2) pair, i.e., a (mu-OH(-))(mu-O(2)CR(-))(2) set. In contrast, 3 and 4 have two different sets of bridging ligands, a (mu-OH(-))(mu-O(2)CR(-))(2) set as in 1 and 2, and a (mu-OR(-))(2)(mu-O(2)CR(-)) set, where RO(-) refers to the alkoxide arm of the hep(-) chelate. Variable-field and -temperature dc magnetization measurements establish that 1 and 2 have S = 5 ground states and significant and positive zero-field splitting parameters (D), whereas 3 and 4 have S = 0 ground states. This dramatic difference of 10 unpaired electrons in the ground state S values for near-isomeric compounds demonstrates an acute sensitivity of the magnetic properties to small structural changes. The factors leading to this have been quantitatively analyzed. The semiempirical method ZILSH, based on unrestricted molecular orbital calculations, was used to obtain initial estimates of the Fe(2) pairwise exchange interaction constants (J). These calculated values were then improved by fitting the experimental susceptibility versus T data, using a genetic algorithm approach. The final J values were then employed to rationalize the observed magnetic properties as a function of the core topologies and the presence of spin frustration effects. The large difference in ground state spin value was identified as resulting from a single structural difference between the two types of complexes, the different relative dispositions (cis vs trans) of two frustrated exchange pathways. In addition, use of the structural information and corresponding J values allowed a magnetostructural correlation to be established between the J values and both the Fe-O bond distances and the Fe-O-Fe angles at the bridging ligands.     

The synthesis and characterisation of some closed polyhedral metallocarbon clusters

Ligands containing unsaturated C₂ and C₄ units have been reacted with triruthenium dodecacarbonyl to produce new organometallic clusters with simple closo-Ru_xC_y polyhedral frameworks which may be regarded as quasi-carboranes. The thermolysis of [Ru₃(CO)₁₂] with 1,4-diphenybutadiene yields the new clusters [Ru₃(CO)₈(μ₃-CPh(CH)₂CPh)] 2 and [Ru₄(CO)₉(μ₄-CPhCCH₂CH₂Ph)] 3, while treatmentof a solution of [Ru₃(CO)₁₂] and diphenylacetylene with trimethylamine N–oxide (Me₃NO) yields [Ru₂(CO)₆(μ-{C₂Ph₂}₂CO)] 4 as the major product and the new cluster [Ru₄(CO)₁₁(μ₄-C₂Ph₂)₂] 5. The solid-state structures of 2, 3 and 5 have been established by single crystal X-ray diffraction analyses and are shown to possess closo-Ru₃C₄ pentagonal bipyramidal, closo-Ru₄C₂ octahedral and closo-Ru₄C₄ dodecahedral skeletons, respectively. The structure and bonding in all three clusters may be rationalised using the Wade–Mingos polyhedral skeletal electron pair approach.     

La6Br10Fe: a La6Fe octahedron with a mixed M6X12/M6X8 type environment

The title compound was synthesized from La, LaBr3, and Fe under Ar atmosphere at 800 degrees C. It crystallizes in space group P4(1) (No. 76) with lattice constants a = 8.255(1) A and c = 30.033(6) A. The structure features an isolated Fe-centered La 6 octahedron with all corners, 9 of its 12 edges, and 3 of its 8 triangular faces coordinated, bridged, or capped by Br atoms. The La6Fe octahedron is significantly distorted, and the La coordination by Br atoms deviates from the common close-packing arrangements found in other reduced rare earth metal halides. Band structure, bonding, and physical properties of the compound have been investigated.     

Synthesis and characterization of glycine copolymers of nylons 6 and 12

Copolymers of glycine and 6-aminohexanoic or 12-aminododecanoic acid within a range of molar compositions from 80/20 to 5/95 were prepared by solution polycondensation of the adequate proportion of the respective pentachlorophenyl ester hydrobromides. Despite their random composition, the copolymers obtained were found to be highly crystalline. Intrinsic viscosities of 2/6 and 2/12 copolyamides were similar and rather low (M_n, ca. 3000-5000). Thermal post-polycondensation allowed to increase the molecular weight of 2/12 copolyamides, so that fibers could be prepared. The composition and sequence distributions were evaluated by means of ¹H- and ¹³C-NMR spectroscopies. Copolyamides were also characterized in terms of thermal properties. Melting and glass transition temperatures are reported. Crystallinity was evaluated from heats of fusion. Crystalline structure was examined by infrared spectroscopy and wide-angle x-ray diffraction. The presence of structures related to the polyglycine I and to α/γ-nylons was confirmed depending on the molar composition. Highly oriented fibers with good tensile properties were obtained from the nylon 2/12 (10 : 90) copolymer. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterisation of [6]-azaosmahelicenes: the first d4-heterometallahelicenes

[6]-Azaosmahelicenes, the first d(4)-heterometallahelicenes, have been synthesised and fully characterised. Their optical properties (UV-Vis absorption and luminescence) are reported.