Unusual flash cooling-induced phase in a crystal of triphenylsilanol.

The unique phase in a crystal of triphenylsilanol (Ph3SiOH) is reported. It is observed that after the crystal is flash-cooled from room temperature to 100 K, a new stable ordered phase II occurs with an increase in the unit-cell parameters compared to the earlier reported phase I. The new phase II occurs upon fast cooling while on slow cooling the disordered phase I is present. Gradual heating from 100 K (phase II) causes the crystal to return to the original phase I at about 150 K. The crystal undergoes the observed transformation in a reversible manner in many consecutive flash cooling/heating cycles without cracking.

First oxido-bridged cubo-octahedral hexanuclear rhenium clusters.

The first discrete hexanuclear metal clusters with cores adopting the M6(µ-O)12 cubo-octahedral topology have been synthesized in the course of a simple one-pot reaction. We present a new class of rhenium clusters which are the first hexanuclear rhenium complexes with 12 bridging ligands and the first clusters with octahedrally arranged Re atoms bridged only by O atoms forming a unique cube-like Re6(µ-O)12 unit. Our synthetic strategy demonstrates a new approach to the syntheses of polynuclear rhenium complexes under mild conditions. We discovered that the [Re6(µ-O)12(3-Mepy)6]BPh4 cluster compound has the ability to undergo reversible or/and quasireversible redox reactions without changing spatial structure and overall geometry. Subsequently, a reduction reaction of [Re6(µ-O)12(3-Mepy)6]BPh4 was performed successfully and almost quantitatively resulting in the formation of the molecular [Re6(µ-O)12(3-Mepy)6] complex.

2,2'-[(1E,2E)-1,2-Bis(hy-droxy-imino)-ethane-1,2-di-yl]dipyridinium hexa-chloridorhenate(IV).

The title salt, (C(12)H(12)N(4)O(2))[ReCl(6)], consists of 2,2'-[(1E,2E)-1,2-bis-(hy-droxy-imino)-ethane-1,2-di-yl]dipyridinium cations and [ReCl(6)](2-) anions which are both located on inversion centres. Each cation consists of a glyoxime moiety attached to two protonated pyridine rings in ortho positions. In the crystal, E,E isomers of the cation are observed which differ in the spatial arrangement of the pyridine rings. These rings are positionally disordered over two positions with site-occupancy factors of 0.786 (7) and 0.214 (7). The geometry of the cation is compared with that of a recently reported dipyridyl-glyoxime with the same configuration. The cations and anions are involved in a network of inter-molecular O-H⋯Cl, N-H⋯Cl and C-H⋯Cl hydrogen bonds.

New coordination modes in potassium edta salts: K2[H2edta]2H2O, K3[Hedta]2H2O and K4[edta]·3.92H2O.

Three potassium edta (edta is ethylenediaminetetraacetic acid, H(4)Y) salts which have different degrees of ionization of the edta anion, namely dipotassium 2-({2-[bis(carboxylatomethyl)azaniumyl]ethyl}(carboxylatomethyl)azaniumyl)acetate dihydrate, 2K(+)·C(10)H(14)N(2)O(8)(2-)·2H(2)O, (I), tripotassium 2,2'-({2-[bis(carboxylatomethyl)amino]ethyl}ammonio)diacetate dihydrate, 3K(+)·C(10)H(13)N(2)O(8)(3-)·2H(2)O, (II), and tetrapotassium 2,2',2'',2'''-(ethane-1,2-diyldinitrilo)tetraacetate 3.92-hydrate, 4K(+)·C(10)H(12)N(2)O(8)(4-)·3.92H(2)O, (III), were obtained in crystalline form from water solutions after mixing edta with potassium hydroxide in different molar ratios. In (II), a new mode of coordination of the edta anion to the metal is observed. The HY(3-) anion contains one deprotonated N atom coordinated to K(+) and the second N atom is involved in intramolecular bifurcated N-H···O and N-H···N hydrogen bonds. The overall conformation of the HY(3-) anions is very similar to that of the Y(4-) anions in (III), although a slightly different spatial arrangement of the -CH(2)COO(-) groups in relation to (III) is observed, whereas the H(2)Y(2-) anions in (I) adopt a distinctly different geometry. The preferred synclinal conformation of the -NCH(2)CH(2)N- moiety was found for all edta anions. In all three crystals, the anions and water molecules are arranged in three-dimensional networks linked via O-H···O and C-H···O [and N-H···O in (I) and (II)] hydrogen bonds. K···O interactions also contribute to the three-dimensional polymeric architecture of the salts.