Nikolai G. Naumov

Unusually high porosity in polymeric cluster cyanides: the synthesis and crystal structure of (H3O)2Zn3[Re6Se8(CN)6]2 20H2O

Abstract Mixing of aqueous solutions of the cluster anion [Re6Se8(CN)6]4− and Zn2+ in the presence of acetic acid (pH 3) leads to precipitation of (H3O)2Zn3[Re6Se8(CN)6]2·20H2O having a three dimensional framework of {Zn3[Re6Se8(CN)6]2}2− formed by Re–CN–Zn covalent interactions. This framework occupies only 41.9% of the unit cell volume. The rest of the space is filled by disordered water molecules and hydroxonium cations.

Excision of the {Mo6Se8} Cluster Core from a Chevrel Phase: Synthesis and Properties of the First Molybdenum Octahedral Cluster Selenocyanide Anions [Mo6Se8(CN)6]7− and [Mo6Se8(CN)6]6−

The synthesis of new molybdenum cluster selenocyanide anionic complexes [Mo6Se8(CN)6]7- and [Mo6Se8(CN)6]6- is reported. The [Mo6Se8(CN)6]7- ion was obtained by excision of the cluster core [Mo6Se8] from a Chevrel phase in the reaction of Mo6Se8 with KCN at 650 degrees C; the [Mo6Se8(CN)6]6- ion is formed by oxidation of [Mo6Se8(CN)6]7-. New cluster salts K7[Mo6Se8(CN)6] x 8H2O (1) and (Me4N)4K2[Mo6Se8(CN)6] x 10H2O (2) were isolated and their crystal structures were solved. Compound 1 crystallizes in the cubic space group Fm3m (a=15.552(2) A, Z=4, V=3761.5(8) A3), compound 2 crystallizes in the triclinic space group P1 (a=11.706(2), b=11.749(2), c=12.459(2) A, alpha=72.25(1), beta=77.51(1), gamma=63.04(1), Z=1, V=1448.5(4) A3). Compound 1 is paramagnetic due to an availability of 21 electrons per Mo6 cluster; cyclic voltammetry reveals a quasi-reversible transition [Mo6Se8(CN)6]7- [Mo6Se8(CN)6]6-, E1/2=0.63 V.

New polymeric structure of rhenium octahedral chalcocyanide complex: Ln3+-derived network with one-dimensional channels

Abstract A novel cyanobridged coordination polymeric complex with octahedral rhenium cyanocluster anion [Re6(μ3−Se)8(CN)6]4− and Nd3+ cation has been synthesised and structurally characterised. Its solid-state structure contains a channel-type polymeric network built from cluster anions and Nd3+ through ReCNNdNCRe interactions. For compound (H3O){Nd(DMF)3(H2O)3}[Re6Se8(CN)6], space group R3c, unit cell parameters are: a=32.514(5); c=25.255(5) A, V=23122(7) A3, Rf=0.0762. A pair of isomorphic complexes has been obtained with Ln=Pr3+,Ho3+.

Access to a novel niobium octahedral cluster core via soft chemistry: synthesis and structure of K2.6Cs3.4[Nb6Cl4O4(OH)4(CN)6]·3H2O containing isolated Nb6Cli4Oi4(OH)i4(CN)a6 cluster unit

Abstract The synthesis and the structure of K 2.6 Cs 3.4 [Nb 6 Cl 4 O 4 (OH) 4 (CN) 6 ]·3H 2 O are described in the present work. It has been obtained by the interaction of Cs 2 Ti 3 Nb 12 Cl 27 O 8 oxychloride with an aqueous solution of potassium cyanide. The crystal structure—determined by single crystal X-ray diffraction at room temperature (monoclinic, C 2/ c , a =13.4336(3) A, b =15.9281(3) A, c =15.9619(3) A, β =90.2177(9)°, V =3415.3(1) A 3 , Z =4)—is built from a novel (Nb 6 O i 4 (OH) i 4 Cl i 4 ) cluster core which exhibits for the first time four hydroxyl groups in addition to four chlorine and four oxygen atoms in inner position; six apical CN ligands complete the coordination of the Nb 6 cluster. Structural and electronic properties of this unit are discussed by comparison with other niobium oxychlorides and oxides based on (Nb 6 Cl 12− x O x ) n + cluster core.

Unprecedented Electron-Poor Octahedral Ta6 Clusters in a Solid-State Compound: Synthesis, Characterisations and Theoretical Investigations of Cs2BaTa6Br15O3

The crystal structure of Cs2BaTa6Br15O3 has been elucidated by using synchrotron X-ray powder diffraction and absorption experiments. It is built from edge-bridged octahedral [(Ta6Bri9Oi3)Bra6]4− cluster units with a singular poor metallic electron (ME) count equal to thirteen. This leads to a paramagnetic behaviour related to one unpaired electron. The arrangement of the Ta6 clusters is similar to that of Cs2LaTa6Br15O3 exhibiting 14-MEs per [(Ta6Bri9Oi3)Bra6]5− motif. The poorer electron-count cluster presents longer metal–metal distances as foreseen according to the electronic structure of edge-bridged hexanuclear cluster. Density functional theory (DFT) calculations on molecular models were used to rationalise the structural properties of 13- and 14-ME clusters. Periodic DFT calculations demonstrate that the electronic structure of these solid-state compounds is related to those of the discrete octahedral units. Oxygen–barium interactions seem to prevent the geometry of the octahedral cluster to strongly distort, allowing stabilisation of this unprecedented electron-poor Ta6 cluster in the solid state.