Vladimir S. Korenev

A New Oxomolybdate Component Extracted from the Virtual Dynamic Library Yielding the Macrocyclic Anion [(MoVI8O28)4(MoV2O2S2)4]24-

A rare isomer of the {Mo(8)O(28)}(8-) anion has been trapped from an acidified aqueous solution of molybdate by using the {Mo(2)O(2)S(2)}(2+) oxothio cation as the linker and isolated as a part of a unique macrocyclic anion, which consists of four isopolyoxomolybdate fragments {Mo(8)O(28)} bridged by four {Mo(2)O(2)S(2)} units.

Unprecedented Linking of Two Polyoxometalate Units with a Metal-Metal Multiple Bond

The reaction of (Bu(4)N)(2)[Re(2)Cl(8)] with lacunary Keggin polyoxometalate K(7)[PW(11)O(39)] in water produces a new dumbbell-shaped heteropolyoxometalate anion, [Re(2)(PW(11)O(39))(2)](8-), whose structure contains a central Re(2) core with a quadruple bond between Re atoms (Re-Re 2.25 A), coordinated to two polyoxometalate units. This complex represents the first example of the direct linking of two polyoxometalate units via a metal-metal multiple bond. The compounds were characterized by X-ray analysis, IR, and electrospray ionization mass spectrometry.

Layered ionic liquid-crystalline organisations built from nano-capsules [Mo132O312S60(SO4)x(H2O)132−2x](12 + 2x)− and DODA+ cations

Two dimethyldioctadecylammonium (DODA+) salts of a new keplerate with the general formula [Mo132O312S60(SO4)x(H2O)132–2x](12 + 2x)− and abbreviated DODAn−Mo132S60 (n = 44, 56) were synthesised and characterised. Both clusters were fully characterised by the combination of Polarised Optical Microscopy, Differential Scanning Calorimetry and Small-angle X-Ray Diffraction showing self-organisation in lamellar (L) liquid crystalline phases. We demonstrated that the lamellar periodicity h of the mesophases can be controlled with the number of DODA+ associated to the clusters. Finally, these new results were compared to those gained from a previously published analogue, the fully oxo keplerate noted DODA36−Mo132 that also self-organise with temperature, but in a slightly more structured lamellar liquid crystalline phase.

Tracking “Apolar” NMe4+ Ions within Two Polyoxothiomolybdates that Have the Same Pores: Smaller Clathrate and Larger Highly Porous Clusters in Action

Two nanosized polyoxothiometalates were synthesized based on linking oxomolybdate building blocks with {Mo2O2S2}(2+) groups. Remarkably, both compounds are formed selectively primarily upon changing the related concentrations in a logical way; they exhibit common structural features based on the same {Mo9O6S3}-type pores, which result in connections between {Mo6O21} pentagons and {Mo2O2S2}(2+) linkers. Whereas the much larger spherical Mo132-type Keplerate contains twenty pores, the smaller Mo63 -type cluster remarkably contains only two. The two compounds and a similar Keplerate exhibit interesting supramolecular properties related to interactions with the unusual predominantly apolar NMe4(+) cations. Structural characterization of the Mo63 -type compound reveals in the solid state a clathrate-like species that contains four NMe4(+) cations embedded in two types of structurally well-adapted pockets. Related NMR spectroscopic investigations in solution using NMe4(+) as the NMR spectroscopic probe are in agreement with the solid-state description. (1)H NMR spectroscopic experiments (1D variable-temperature, 2D total correlation spectroscopy (TOCSY), exchange spectroscopy (EXSY), and diffusion-ordered spectroscopy (DOSY)) feature firmly immobilized and mobile NMe4(+) ions in relationship with the type of host-guest arrangements. The use of the (1)H NMR DOSY spectroscopic methodology has been successfully applied to track the interactions of the NMe4(+) cations with the {Mo9O6S3} pores of a sulfurated Keplerate, thereby allowing the first quantitative analysis of this type of plugging process. The stability constant K=(210±20) mol(-1)  L is discussed related to the character of the process.

Synthesis and crystal structure of Cs7[BW12O40][Rh2(CH3COO)4Cl]2 · 8H2O

The binary salt Cs7[BW12O40][Rh2(CH3COO)4Cl]2 · 8H2O was obtained by heating of K8[HBW11O39] · 13H2O with [Rh2(CH3COO)4(H2O)2] in water followed by crystallization in the presence of CsCl. The crystal structure of the salt was determined by X-ray diffraction. Its ionic structure consists of the Cs+ cations, the Keggin-type heteropoly anions [BW12O40]5−, and the polymeric chain anions catena-[Rh2(CH3COO)4Cl]nn−.

Nanoscale hydrophilic colloids with high relaxivity and low cytotoxicity based on Gd(III) complexes with Keplerate polyanions

The work introduces for the first time Mo-132-type Keplerates (Kp) and Gd3+ ions as a basis for the one-pot synthesis of aqueous colloids with high longitudinal relaxivity (r1 = 96.4 mM−1 s−1 at 20 MHz). The hydrophilic coating of small (3–5 nm) Gdx(Kp)y-based cores provides their colloid stabilization, protection from degradation and low cytotoxicity.

Molecular recognition of Ca2+ cations by internal and external receptors/interfaces in a spherical porous molybdenum-oxide capsule: unusual coordination scenarios

The unique molybdenum-oxide capsule [{(MoVI)MoVI5O21(H2O)6}12{MoV2O4(SO4)}30]72− shows an unprecedented affinity towards Ca2+ cations which interact in fully or partially hydrated forms with different well-defined internal and external receptor areas via direct coordination and/or hydrogen bonds. The cavity of the capsule comprises an unusual “water assembly” of the Ca20{H2O}60Ca20{(H2O)5}12 type. Altogether, we can refer to a unique solid-state structure.

Xanthate complexes of {Nb2S4}4+

Alkyl xanthate complexes [Nb2S4(S2COR)4] (R = Et (I), iso-Pr (II), n-Bu (III), and iso-Am (IV)) are synthesized by the ligand exchange reaction in solutions from (Et4N)4[Nb2S4(NCS)8] and the corresponding potassium salts in satisfactory yields. The X-ray diffraction analyses are carried out for the isopropyl xanthate (II) and butyl xanthate (III) complexes. From the view point of mutual arrangement of chelate cycles, complexes II and III exist in crystals as ΛΔ isomers. The niobium-niobium distances are 2.8789(4) Å in complex II and 2.8856(3) Å in complex III. The first example for the formation of short S...S contacts between the disulfide ligands of the {Nb2S4}4+ fragments in the crystal structure of III is found (3.146 Å).

Crystal structure of two salts derived from paratungstate in the [H2W12O42]10− anion

Novel mixed salts of the paratungstate anion Na2(NH4)8[H2W12O42]·12H2O (1) and Na7.5K2.5[H2W12O42]··22.2H2O (2) are obtained by slow concentration of tungstate solutions and characterized by single crystal X-ray diffraction.

Synthesis and crystal structure of the binuclear complex Cs3[Mo2VO2(μ-S)2Cl4(H2O)2]Cl

The destruction of hydroxy and aqua bridges of the cyclic pentamer K2I2[Mo10O10(μ-S)10(OH)10(H2O)5] · 20H2O (I) in HCl in the presence of CsCl gave a new binuclear oxothiomolybdenic complex Cs3[Mo2O2(μ-S)2Cl4(H2O)2]Cl (II), which was isolated and characterized by X-ray crystallography. The dimeric fragment in complex II consists of two distorted octahedral Mo(V) centers, which have non-equivalent environment and are connected by two sulfide bridges. The Mo-Mo distance (2.8411(6) Å) in II corresponds to a metal-metal bond.