Aspect-ratio dependent oscillatory thermocapillary convection in the floating half zone

The dependency of the critical Marangoni number on the geometrical aspect ratio of the floating half zone is essential to predict the onset of oscillatory thermocapillary convection.The experimental studies in the microgravity conditions on floating half zones of several centimeters in diameter have predicted that the critical Marangoni number increases with the increasing aspect ratio,and the terrestrial experimental studies have predicted the contradictory conclusion for floating half zones of several mil...     

Non-Gravitational Effects with Density-Matching in Evaluating the Influence of Sedimentation on Colloidal Coagulation

The method of density matching between the solid and liquid phases is often adopted to effectively eliminate the effect of sedimentation of suspensions in studies on dynamic behaviour of a colloidal system. However, the associated changes in the solvent composition may bring side effects to the properties investigated and therefore might lead to a faulty conclusion if the relevant correction is not made. To illustrate the importance of this side effect, we present an example of the sedimentation influence on the coagulation rate of suspensions of 2μm （diameter） polystyrene. The liquid mixtures, in the proper proportions of water （H2O）, deuterium oxide （D2O） and methanol （MeOH） as the liquid phase, density-matched and unmatched experiments are performed. Besides the influence of viscosity, the presence of methanol in solvent media, used to enhance the sedimentation effect, causes significant changes （reduction） in rapid coagulation rates compared to that in pure water. Without the relevant corrections for those non-gravitational factors it seems that gravitational sedimentation would retard the coagulation. The magnitude of the contribution from the non-gravitational factor is quantitatively determined, making the relevant correction possible. After necessary the influence of the sedimentation on coagulation rates at corrections for all factors, our experiments show that the initial stage of the coagulation is not observable.     

Synthesis and molecular structure of chlorostannyl derivatives of carbonyl(cyclopentadienyl)nitrosylmanganese

The reaction of [CpMn(CO)(NO)]₂ (I) with an equimolar amount of tin dichloride in THF at room temperature gave the product of tin insertion into the Mn-Mn bond, the carbonyl nitrosyl complex [CpMn(CO)(NO)]₂SnCl₂ (II). The same complex was formed on treatment of CpMn(CO)(NO)SnCl₃ with sodium borohydride. Treatment of I with an excess of anhydrous tin dichloride under the same conditions gave the trinitrosyl complex Cp₂Mn₂(NO)(μ-NO)₂SnCl₃ (III). According to X-ray diffraction, II contains a Mn-Sn-Mn chain with highly shortened Mn-Sn bonds (2.5570(2) and 2.5754(2) Å). Compound III contains a Mn-Mn-Sn chain (Mn-Mn, 2.5358(10); Mn-Sn, 2.5604(8) Å) with the Mn-Mn bond supplemented by two nitrosyl bridges and one terminal NO group.     

Electrochemical behavior of heterometallic chalcogenide clusters

The electrochemical properties of sixteen tri- and tetranuclear chalcogenide-bridged heterometallic clusters in comparison with the tetrahedral clusters Cp′₄M₄S₄ (M = Cr, V; Cp′ = CH₃C₅H₄) simulating ferredoxins were studied. For complexes with μ₄-coordination of the chalcogen, only reduction processes involving the metal-heterometal bonds are reversible. For complexes with μ₃-coordination of the chalcogen, the oxidation processes are reversible except for triiron-chalcogen-pnicogenide clusters having an easily and reversibly oxidizable E-Fe(CO)₂C₅H₄Bu-t bond (E = Sb, Bi) at the pnicogen atom. The electron-compensating role of the lone pair at the bridging chalcogen atom in the stabilization of the oxidation products of the clusters is discussed.     

Syntheses and structures of nickel–tungsten μ-tellurophenyl complexes CpNi(PPh<Subscript>3</Subscript>)(μ-TePh)W(CO)<Subscript>5</Subscript> and [CpNi(PPh<Subscript>3</Subscript>)(μ-TePh)]<Subscript>2</Subscript>W(CO)<Subscript>4</Subscript>

Syntheses and molecular structures of the heterometallic complexes of nickel cyclopentadienyl triphenylphosphine tellurophenolate with tungsten carbonyls (II and III) (CIF files CCDC nos. 1559733 and 1559734, respectively) are described.     

Synthesis and molecular structure of [((CO)3RuBr2)2(μ-SePh)2Ru(CO)4] cluster with a Ru3Se2 chain core

Treatment of ruthenium carbonyl, [Ru₃(CO)₁₂] with phenylseleno tribromide PhSeBr₃ afforded a new triruthenium cluster, [(CO)₁₀Br₄Ru₃(μ-SePh)₂] (1). Its molecular structure was determined by single crystal XRD method (P2₁/c; a = 10.514(3) Å; b = 10.814(3) Å; c = 19.063(5) Å; β = 105.064(4)°; V = 2093.1(10) Å³) and shown to have two lateral Ru(CO)₃Br₂ units attached via two PhSe bridges to a Ru(CO)₄ center forming a chain-like Ru-Se-Ru-Se-Ru cluster core. This is in contrast with a recently reported reaction of PhTeBr₃ with [Ru₃(CO)₁₂] which formed a monomeric complex of ruthenium-dicarbonyl-dibromo fragment coordinating two PhTeBr ligands, [(CO)₂RuBr₂(PhTeBr)₂].