Tetrahedral Metal Clusters Research Articles

Intermetallic Compounds KnMm (М = Ag, Au, As, Sb, Bi, Ge, Sn, Pb): Geometrical and Topological Analysis, Cluster Precursors, and Self-Assembly of Crystal Structures

A geometrical and topological analysis and simulation of the self-assembly of the crystal structures of intermetallic compounds formed in the K–M (M = Ag, Au, As, Sb, Bi, Ge, Sn, Pb) systems have been performed using computation methods (the ToposPro software). The precursor metal clusters of KnMm crystal structures are determined based on the algorithms of structure-graph decomposition in cluster structures and construction of the basic net of structure in the form of a graph with nodes corresponding to cluster centers. Tetrahedral metal clusters, forming packings in the K3Bi-cF16, K3Bi-hP8, K2As2-oP16, K2Sb2-mP16, and K2Sb2-mP32 crystal structures; tetrahedral metal clusters and spacers for the K(K2As2)2-mC18, K4(Pb4)-tI64, and K2(Au4)-hP12 structures; polyhedral metal clusters KK4Pb12 and spacers for the Pb12K(K4Pb12)-cI58 structure; and dodecahedral metal clusters KGe20 and spacers for the K3Ge3(KGe20)-cP54 structure have been found. The symmetry and topology code of the self-assembly of crystal structures of intermetallic compounds KnMm has been reconstructed from precursors $$S_{3}^{0}$$ in the following form: primary chain $$S_{3}^{1}$$ → microlayer $$S_{3}^{2}$$ → microframework $$S_{3}^{3}$$ .

Intermetallic Compounds NakMn (М = K, Cs, Ba, Ag, Pt, Au, Zn, Bi, Sb): Geometrical and Topological Analysis, Cluster Precursors, and Self-Assembly of Crystal Structures

A geometrical and topological analysis has been performed, and self-assembly of the crystal structures of intermetallic compounds formed in the Na–M (M = K, Cs, Ba, Ag, Pt, Au, Zn, Bi, Sb) systems has been simulated using computer methods (the ToposPro software). The NakMn precursor metal clusters of the crystal structures are determined based on the algorithms of structural-graph decomposition in cluster structures and construction of the basic net of the structure in the form of a graph whose nodes correspond to the cluster centers. The tetrahedral metal clusters M4, forming packets in the Na3Bi-hP8, Na2Bi2-tP4, and Na2Sb2-mP16 crystal structures; tetrahedral metal clusters M4 and spacers for the Na2(Au4)-cF24 and Ba2(Na4)-hP12 framework structures; octahedral clusters M6 for the Na4Au2-tI12 structure; octahedral M6 and tetrahedral M4 metal clusters for the Na2(Na4)(Ba6)-cF96 and Au2(In4)(Na6)-cF96 structures; and icosahedral metal clusters M13 for the Na(Zn13)-cF116 structure are found. The symmetry and topology code of the self-assembly of crystal structures of NakMn intermetallic compounds has been reconstructed from precursor metal clusters $$S_{3}^{0}$$ in the following form: primary chain $$S_{3}^{1}$$ → microlayer $$S_{3}^{2}$$ → microframework $$S_{3}^{3}$$ .

Intermetallic Compounds LikMn (M = Ag, Au, Pt, Pd, Ir, Rh): Geometrical and Topological Analysis, Tetrahedral Cluster Precursors, and Self-Assembly of Crystal Structures

A combinatorial and topological analysis has been performed and self-assembly of the crystal structures of intermetallic compounds formed in the Li–M (M = Ag, Au, Pt, Pd, Ir, Rh) systems has been simulated using computer methods (the TOPOS program package). The LikMn precursor metal clusters are determined based on the algorithms of graph expansion in cluster structures and construction of basic 2D and 3D nets in the form of graphs, the nodes of which correspond to the cluster centers. The tetrahedral metal clusters M4, forming packets in the (LiPd3)(Pd4)-cF32, (Li2Rh2)(Rh4)-oI8, (Li2Pd2)(Pd4)-mP4, LiAu3-cP4, Li1.84Ag2.16-cF4, Li2Ag2-tI8, Li2Pd2-cP2, Li2Rh2-hP2, and Li3Pd-cF16 crystal structures; tetrahedral metal clusters M4 and spacer atoms for the Li2(Pt4)-сF24 framework structure; and two-layer clusters 0@М4@M22 for the (Li4)(Li12Ag10)-cI52 structure are found. The symmetry and topology code of self-assembly of the crystal structures of LikMn intermetallic compounds has been completely reconstructed from precursor metal clusters $$S_{3}^{0}$$ in the following form: primary chain $$S_{3}^{1}$$ → microlayer $$S_{3}^{2}$$ → microframework $$S_{3}^{3}$$.

Universal mechanism of tetrahedral metal cluster formation in structures with breathing pyrochlore sublattices

Universal mechanism of tetrahedral metal cluster formation in structures with breathing pyrochlore sublattices

Modeling of the self-organization processes in crystal-forming systems. Tetrahedral metal clusters and the self-assembly of crystal structures of intermetallic compounds

A combinatorial and topological modeling of 1D, 2D, and 3D packings of symmetrically linked A4 tetrahedra has been performed. Three types of 1D chains with tetrahedra connectivities of 4, 6, and 8 were used to model 2D layers L-1, L-2, and L-3 and 3D frameworks FR-1, FR-2, FR-3, and FR-4. A family of tetrahedral structures with FR-1, FR-2, and FR-3 frameworks has been selected among the intermetallic compounds with chemical compositions of A 3 B, A 2 B 2, AB 3, A 2 BC, AB 2 C, and ABCD; this family includes more than 1900 compounds (TOPOS program package). It is found that the topological models of tetrahedral 3D frameworks are in correspondence with all types of the crystal structures formed in Au–Cu binary systems (FR-1 for Cu3Au (auricupride), Cu2Au2 (tetraauricupride), and CuAu3 (bogdanovite)), in the Mg–Cd system (FR-3 for Mg3Cd, Mg2Cd2, and MgCd3), in the Li–Hg system (FR-2 for Li3Hg and Li2Hg2 and FR-3 for LiHg3), in the Li–Ag–Al ternary system (FR-2 for LiAg2Al and Li2AgAl), and in the Li–Mg–Pd–Sn quaternary system (FR-2 for LiMgPdSn). Framework FR-4 has been established in ternary intermetallic compounds A(Li2Sn2); A = Cu, Ag, Au.

ChemInform Abstract: An Example of the Coexistence of Octahedral with Tetrahedral Metal Clusters: The Ternary Phosphide Ni4Nb5P4. Structural and Theoretical Analyses.

Abstract The ternary compound Ni 4 Nb 5 P 4 has been synthesized and investigated by means of X-ray powder diffraction. The tetragonal unit cell dimensions are a = 9.9304(4) A and c = 3.5243(3) A (space group I4/m, Z=2). The crystal structure has been refined by the Rietveld method (R F = 0.036 and R p = 0.128 for 210 reflexions and 30 refined parameters) using the structure Cu 4 Nb 5 Si 4 of Ti 5 Te 4 type as related model. In me structure, there is no interaction between the metalloid atoms, while Nb-Nb and Ni-Ni bonding leads to the formation of octahedral Nb 6 and tetrahedral Ni 4 clusters. Along the [001]direction of the tetragonal lattice, the Nb 6 clusters condense via opposite apices while the Ni 4 ones share common edges. The structure can be viewed as a fully original structure with infinite linear chains of Nb 6 octahedra and Ni 4 tetrahedra in a phosphorus network. Up to now, such a coexistence of Nb 6 octahedral together with Ni 4 tetrahedral clusters has never been mentioned in solid state chemistry. Tight-binding calculations have been performed in order to analyse the bonding in this ternary compound. In particular, they show that the valence electron count associated with a Nb 5 P 4 repeat unit is 45e, i.e the Ni 0 atoms donate zero electron to the Nb 5 P 4 substructure. A survey of ternary compounds which also exhibit metal clusters, based on tetrahedral M 4 units (M = Fe, Ni, Cu) is also reported.

Metal−Metal Bonding and Correlated Metallic Behavior in the New Deficient Spinel Ga0.87Ti4S8

We have synthesized and characterized the first Ti member of the AM4X8 (A = Ga, Ge; M = V, Nb, Ta, Mo, X = S, Se) family of compounds that exhibit a deficient spinel structure with tetrahedral transition metal clusters. Single-crystal X-ray structure determination of Ga0.87Ti4S8 (space group F−43m, a = 9.9083(11) Å) revealed the presence of Ga vacancies and a partial declustering of the transition metal atoms compared to other members of the family. This declustering is likely associated to the decrease of the electronic filling of the clusters from 7 to 11 electrons in known AM4X8 compounds to ∼3 electrons in Ga0.87Ti4S8. XPS measurements show that the valence band of Ga0.87Ti4S8 is more dispersed than that of the Mott insulator GaV4S8, which suggests a strengthening of the transfer integrals induced by the slackening of the transition metal clusters. A Fermi step consistent with a metallic character is observed in Ga0.87Ti4S8 while a gap appears (0.2 eV) below the Fermi level in the Mott insulator GaV4S8. The resistivity measured on crystals of Ga0.87Ti4S8 showed a metallic behavior with a small residual resistivity ratio. Ga0.87Ti4S8 exhibits large electronic specific heat (γ = 58 mJ K−2 mol−1) and Pauli susceptibility. All these measurements as well as the Wilson and Kadowaki-Woods ratios demonstrate that Ga0.87Ti4S8 exhibits a correlated metal type behavior and is no longer a paramagnetic Mott insulator like other members of the family.

Bonding in Methylalkalimetals (CH3M)n(M = Li, Na, K;n= 1, 4). Agreement and Divergences between AIM and ELF Analyses

The chemical bonding in methylalkalimetals (CH(3)M)(n)() (M = Li-K; n = 1, 4) has been investigated by making use of topological analyses grounded in the theory of atoms in molecules (AIM) and in the electron localization function (ELF). Both analyses describe the C-M bond as an ionic interaction. However, while AIM diagnoses a decrease of ionicity with tetramerization, ELF considers tetramers more ionic. Divergences emerge also when dealing with the bonding topology given by each technique. For the methylalkalimetal tetramers, the ELF analysis shows that each methyl carbon atom interacts through a bond pair with each of the three hydrogen atoms belonging to the same methyl group and through an ionic bond with the triangular face of the tetrahedral metal cluster in front of which the methyl group is located. On the other hand, the AIM topological description escapes from the traditional bonding schemes, presenting hypervalent carbon and alkalimetal atoms. Our results illustrate that fundamental concepts, such as that of the chemical bond, have a different, even colliding meaning in AIM and ELF theories.

Gold‐Caged Metal Clusters with Large HOMO—LUMO Gap and High Electron Affinity.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Gold-Caged Metal Clusters with Large HOMO−LUMO Gap and High Electron Affinity

We report a series of isoelectronic gold-caged metal clusters, M@Au14 (M = Zr, Hf), and anion clusters, M@Au14- (M = Sc, Y), all having a calculated HOMO-LUMO gap larger than the well-known tetrahedral cluster Au20-the 3D metal cluster with a very large measured HOMO-LUMO gap (1.77 eV). The clusters M@Au14 (M = Sc, Y) also exhibit a calculated electron affinity (EA) and vertical detachment energy (VDE) not only higher than the "superhalogen" icosahedral Al13 cluster but also possibly even higher than a Cl atom which has the highest (measured) elemental EA or VDE (3.61 eV).

Direct optical resolution of the enantiomers of novel chiral tetrahedral metal clusters by HPLC on a cellulose tris-(3,5-dimethylphenylcarbamate) stationary phase.

The enantioseparation of seven novel chiral transition metal tetrahedral clusters has been achieved for the first time on cellulose derivatized with tris(3,5-dimethylphenylcarbamate) (CDMPC) as chiral stationary phase (CSP) and hexane containing different alcohols as modifiers as mobile phases. The effect of mobile-phase composition on enantioselectivity was studied, and the effect of structural variation of the solutes on their enantioseparation was also investigated. It was found that both the metal in the tetrahedral core and the ligand coordinated to the atom in the tetrahedral core had significant effects on the chromatographic behavior of the analytes.

Synthesis of Optically Active Tetrahedral Clusters through Ester Exchange Catalyzed by Lipase

Reactions of the monoanions [(η 5 -C 5 H 4 R)M 2 (CO) 3 ] - with ArCH(Me)COOCH 2 C 2 H(μ 3 -C)Co 2 -(CO) 6 (4) in THF at 60 °C gave the functional cluster derivatives ArCH(Me)COOCH 2 C 2 H-(μ 3 -C)CoM 2 (CO) 5 (η 5 -C5H4R) (la-d: M 2 = Mo, W; R = CO 2 Me, C(O)Me). Similarly, reactions of [(η 5 -C 5 H 4 )C(O)OCH 2 (OH)CH 3 ]M 2 (CO) 3 } - (M 2 = Mo, W) with (μ 3 -S)M 1 Co 2 (CO) 9 (M 1 = Fe, Ru) gave the tetrahedral metal clusters (μ 3 -S)CoM 2 M 1 (CO) 8 [(η 5 -C 5 H 4 )C(O)OCH 2 (OH)CH 3 ] (8a-d: M 1 = Fe, Ru; M 2 = Mo, W). Treatment of the two metal clusters la-d and three metal clusters 8a-d with methanol respectively in the presence of lipase at 50 °C for 1 h afforded the optically active cluster derivatives HOCH 2 C 2 H(μ 3 -C)CoM 2 (CO) 5 (η 5 -C 5 H 4 R) (6a-d: M 2 = Mo, W; R = CO 2 Me, C(O)Me) and (μ 3 -S)CoM 2 M 1 (CO) 8 [(η 5 -C 5 H 4 )C(O)OCH 3 ] (9a-d: M 1 = Fe, Ru; M 2 = Mo, W). The products were separated by silica gel chromatography. The conditions of the lipase reactions were discussed. All the compounds in the global process were characterized by element analysis, and IR and 1 H NMR spectroscopy. The structures of clusters 8c and 9c have been determined by single-crystal X-ray diffraction.

Direct resolution of novel tetrahedral metal clusters on a cellulose tris‐(3,5‐dimethylphenylcarbamate) chiral stationary phase by high‐performance liquid chromatography

AbstractDirect optical resolution of five novel tetrahedral heterometal cluster enantiomers has been achieved for the first time on a cellulose tris‐(3,5‐dimethylphenylcarbamate) chiral stationary phase, using hexane as the mobile phase with various alcohols as modifiers. UV detection was carried out at 254 nm. The influence of the mobile phase composition on enantioselectivity is discussed and optimum resolution has been achieved. The effect of structural variation of the solutes on their enantioseparation has also been investigated.

Tetrahedral and heteronuclear transition metal clusters through isolobal displacements and functional transformations

The isolobal reaction of the tetrahedral cluster Ph2C2Co2(CO)6with η5-CHOC5H4(CO)3MNa (M = Mo, W) yields η5-CHOC5H4MCoC2Ph2(CO)5 [(1) M = Mo, (2) M = W], whereas M–M singly-bonded dimers [η5-RC5H4- M(CO)3]2 [M = Mo, R = Ac; M = Mo, W, R = CHO] react with Co2(CO)8 to give η5-AcC5H4MoCo3(CO)11(7) and η5-C5H5MCo3(CO)11 [(8) M = Mo, (9) M = W], respectively. While (1) and (2) react with 2,4-dinitrophenylhydrazine to give phenylhydrazone derivatives η5-2,4-(NO2)2C6H3NHN=CHC5H4MCoC2Ph2(CO)5 [(3) M = Mo, (4) M = W], treatment of η5-AcC5H4MCoFe(CO)8(μ3-S) with 2,4-dinitrophenylhydrazine produces corresponding derivatives η5-2,4-(NO2)2C6H3NHN=C(Me)C5H4MCoFe(CO)8(μ3-S) [(5) M = Mo, (6) M = W]. In addition, the cyclopentadienylformaldehyde ligand in the η5-CHOC5H4MoCoFe(CO)8(μ3-S) cluster can be decarbonylated in the presence of Co2(CO)8 to give the parent cluster η5-C5H5MoCoFe(CO)8(μ3-S)(10). This observation, together with the formation of (8) and (9) in the presence of Co2(CO)8 can be explained by the proposed mechanism.

Novel tetrahedral and heteronuclear transition metal clusters prepared via single and double isolobal displacements

Ten transition metal cluster complexes with parent and substituted cyclopentadienyl ligands, [(η5-C5H4 CH2CH2)2O][MFeCoS(CO)8]2 (2 M = Mo; 3 M = W), (η5-C5H5)(η5-RC5H4)MFeNiS(CO)5 (5 M = Mo, R = Me; 6 M = W, R = H), (η5-C5H5)[η5-C5H4C(O)CH2]2[WFeNiS(CO)5][WFeCoS(CO)8] (8), (η5-C5H5)2[η5-C5H4 C(O)CH2]2[WFeNiS(CO)5]2 (9), (η5-RC5H4)[(η5-C5H4CH2CH2)2O][Mo2FeS(CO)7][MoFeCoS (CO)8] (10 R = MeCO; 12 R = MeO2C), (η5-RC5H4)2[(η5-C5H4CH2CH2)2O][Mo2FeS(CO)7]2 (11 R = MeCO; 13 R = MeO2C), were synthesized through single and double isolobal displacements and characterized by elemental analyses, i.r., 1H-n.m.r. and MS techniques.

The Interpretation of the Terminal ν(CO) Spectra of Some Tetranuclear Carbonyl Clusters

The recently suggested spherical (SHM) and tensor (THM) harmonic models are applied to the interpretation of the terminal ν(CO) spectra of twenty six tetrahedral transition metal clusters containing between four and twelve terminal carbonyl groups. Although the SHM is perhaps the more generally relevant, there are species for which the THM is appropriate as a first approximation. The distinction between the two appears to be associated with a disruption of the band structure of the cluster either by the introduction of heterometal atoms or by the presence of a group – acetate ester, halide or hydride – presumably acting as an electronegative substituent.

An example of the coexistence of octahedral with tetrahedral metal clusters: the ternary phosphide Ni 4Nb 5P 4. Structural and theoretical analyses

The ternary compound Ni 4Nb 5P 4 has been synthesized and investigated by means of X-ray powder diffraction. The tetragonal unit cell dimensions are a = 9.9304(4) Å and c = 3.5243(3) Å (space group I4/m, Z=2). The crystal structure has been refined by the Rietveld method (R F = 0.036 and R p = 0.128 for 210 reflexions and 30 refined parameters) using the structure Cu 4Nb 5Si 4 of Ti 5Te 4 type as related model. In me structure, there is no interaction between the metalloid atoms, while Nb-Nb and Ni-Ni bonding leads to the formation of octahedral Nb 6 and tetrahedral Ni 4 clusters. Along the [001]direction of the tetragonal lattice, the Nb 6 clusters condense via opposite apices while the Ni 4 ones share common edges. The structure can be viewed as a fully original structure with infinite linear chains of Nb 6 octahedra and Ni 4 tetrahedra in a phosphorus network. Up to now, such a coexistence of Nb 6 octahedral together with Ni 4 tetrahedral clusters has never been mentioned in solid state chemistry. Tight-binding calculations have been performed in order to analyse the bonding in this ternary compound. In particular, they show that the valence electron count associated with a Nb 5P 4 repeat unit is 45e, i.e the Ni 0 atoms donate zero electron to the Nb 5P 4 substructure. A survey of ternary compounds which also exhibit metal clusters, based on tetrahedral M 4 units (M = Fe, Ni, Cu) is also reported.

Dynamic Isomerization of a Supramolecular Tetrahedral M4L6 Cluster1

The bis-hydroxamate ligand isophthal-di-N-(4-methylphenyl)hydroxamate (E) forms tetrahedral clusters of the type M4E6 (M = Ga(III), Fe(III)). The syntheses of these and several other tetrahedral metal clusters have illustrated a general approach to the design of supramolecular metal clusters based on incommensurate coordination number interactions. In each case, rigid spacers separate bidentate units and preclude formation of metal coordination species other than the one targeted. For the Ga4E6 cluster described here each vertex is a chiral metal center (Δ or Λ) that generates clusters with T (ΔΔΔΔ or ΛΛΛΛ), C3 (ΔΔΔΛ or ΛΛΛΔ), or S4 (ΔΔΛΛ) symmetry. The rigid ligand spacer is bimodal, accommodating either mixed or homochiral metal centers at either end, but locks in the chirality of the complex once formed. Therefore all three isomers are seen in solution and their interconversion, although still on the NMR time scale, is significantly slower than isomerization of similar unimolecular hydroxamate complexes. The distribution of the isomers in aqueous solution for the T, C3, and S4 isomers is 4, 58, and 38%, respectively. The barrier to the interconversions, which occur through a nondissociative trigonal twist at the metal centers, is 58 kJ mol-1 for each of the isomerization steps. The syntheses of the ligand and corresponding iron and gallium complexes are described. The compound Ga4E6·18 DMF (DMF = dimethylformamide) crystallizes in I41/a with Z = 8, a = 24.0738(2) Å, and c = 68.5828(5) Å. Full-matrix refinement of data collected on a CCD detector with 7710 observations and 576 variables gave an R factor (on F) of 0.089. Two crystallographically independent clusters are chemically equivalent, both lying on 4̄ special positions. The Ga-to-Ga distances between metal centers with like and opposite chiralities are 9.0 and 8.8 Å, respectively. Two different ligand conformations are observed: one bridging homochiral metal centers and the other mixed chiral centers. Their nearly equal stability explains the mix (T, C3, S4) of cluster isomers seen. This ligand couples the metal vertices in the cluster so as to increase significantly the transition state free energy for Λ−Δ interconversion but does not couple the chirality for the Λ or Δ ground state.

Synthesis of Triangular and Tetrahedral Heteronuclear Metal Clusters Using Hydride Complexes of Cyclopentadienylrhodium and -ruthenium as the Precursors

Photochemical and/or thermal reactions of Cp*Rh(H)2(SiEt3)2 (Cp* = η5-C5Me5) with the dimeric metal complexes [CpNi(CO)]2 (Cp = η5-C5H5), [CpCo(NO)]2, [CpRu(CO)2]2, and [CpFe(CO)2]2 yielded the tri...

Delocalized bonding in tetrahedral organo-transition metal clusters: an EHMO study of metal vertex rotations in Co2Fe(CO)9S, CpMoCo2(CO)8CR, and in Cp2Mo2(CO)4(RC≡CR)

Molecular orbital calculations at the extended Hückel level are used to rationalize the barriers to vertex rotation in the tetrahedral metal cluster complexes FeCo2(CO)9S, 2, and (C5H5)MoCo2(CO)8CH, 3. It is shown that, in accord with experimental observations on 2, rotation of an Fe(CO)3 fragment through 60° brings about a weakening of the metal–metal bonding interactions within the FeCo2 triangle. In the MoCo2 cluster, 3, rotation of the CpMo(CO)2 fragment about an axis joining the molybdenum to a central point within the tetrahedron gives rise to three minima in which the cyclopentadienyl ring is oriented proximal or distal relative to the capping carbynyl moiety, or in the plane of the three metals. The rotation trajectory of the CpMo(CO)2 vertices in Cp2Mo2(CO)4(HC≡CH), 4, has been elucidated by means of a Bürgi–Dunitz analysis of the X-ray crystal structures of a series of related clusters in which the CpMo(CO)2 units exhibit a range of orientations. The calculations suggest that the barriers to vertex rotations in 4 are primarily of steric rather than electronic origin. Key words: metal clusters, vertex rotations, EHMO calculations.