A cluster Pt-Sn-catalyst for the ethanol direct oxidation

A bimetallic platinum-tin catalyst is synthesized by depositing on highly dispersed carbon black from a cluster of the corresponding metals with atomic ratio in the surface layer 2: 1. The obtained catalyst was characterized by X-ray diffraction and electron-dispersion analyses, laser mass-spectrometry, and transmission electron microscopy. According to voltammetry data, specific characteristics of the synthesized cluster catalyst in the reaction of ethanol direct oxidation are superior to those of the platinum-tin catalyst described in literature.     

Oxidative addition of the Mo-Cl bond to the Pt0 complex. Synthesis and structure of Cp′Mo(μ-CO)2(C2Ph2)Pt2(PPh3)2(CO)Cl

A reaction of Cp′Mo(CO)₃Cl(Cp′ = MeC₅H₄) with (PPh₃)₂Pt(C₂Ph₂) gave the heterometallic cluster Cp′Mo(μ-CO)₂(C₂Ph₂)Pt₂(PPh₃)₂(CO)Cl (I) as the sole product. According to X-ray diffraction data, complex I contains single Pt-Mo bonds (2.7962(5) and 2.7699(5) ?) but no Pt-Pt bond (Pt…Pt 2.9746(3) ?). The coordinated diphenylacetylene molecule forms two Pt-C σ-bonds (2.054(6) and 2.083(5) ?) and a π-bond to the Mo atom (Mo-C 2.265(6) and 2.272(5) ?; C≡C 1.387(8) ?). Original Russian Text ? A.A. Pasynskii, I.V. Skabitskii, Yu.V. Torubaev, S.S. Shapovalo, 2009, published in Koordinatsionnaya Khimiya, 2009, Vol. 35, No. 6, pp. 410–413.     

Diphenyldichalcogenide complexes of iron, chromium and rhenium carbonyls

The substitution of a labile THF ligand in Cr(CO)₅(THF) by the Ph₂Se₂ molecule provided the monomeric complex Cr(CO)₅(Ph₂Se₂) (I). The similar diiodo-tricarbonyl-iron complex (CO)₃FeI₂(Ph₂Se₂) (II) (along with [(CO)₃Fe(??-SePh)₃Fe(CO)₃]⁺(I₅)^? (III) as a by-product) was separated upon the treatment of ??phenylselenyl iodide?? [PhSeI] with iron pentacarbonyl, Fe(CO)₅. Complex II is isostructural with the known tellurium-containing analogue, (CO)₃FeI₂(Te₂Ph₂). The latter have provided the dimeric tellurophenyl bridged iodo-tricarbonyl-iron complex [(CO)₃IFe(??-TePh)]₂ (IV) under action of the excess of Fe(CO)₅. Its bromide analogue [(CO)₃BrFe(??-TePh)]₂ (V) was prepared upon the treatment of PhTeBr with the excess of Fe(CO)₅. The reaction of [PhSeI] with Re(CO)₅Cl afforded only [(CO)₆Re₂(??-I)₂(??-Se₂Ph₂)] (VI) in contrast to the (CO)₃Re(PhTeI)₃(??₃-I) formation in similar known reaction of [PhTeI]. The molecular and crystal structures of I?CVI is discussed.     

Synthesis and molecular structure of niobocene trimethylacetate and its π-complex with diphenylacetylene

Niobocene trimethylacetate Cp₂Nb(OOCCMe₃) (I) does not react with usual n-donors (pyridine and triphenylphosphine), but readily adds a π-acceptor molecule of diphenylacetylene (tolane) in benzene to form Cp₂Nb(OOCCMe₃)(π-Ph₂C₂) · 0.5 C₆H₆ (II). The structures of the diamagnetic complexes I and II have been determined by an X-ray diffraction study. These molecules represent wedge-like sandwiches wit dihedral angles between cyclopentadienyl ligands equal to 44.4 and 50.7°, and average NbC distances of 2.39 and 2.44 Å, respectively. The bisector plane of I contains the chelate trimethylacetate group (NbO bond lenghts 2.23 and 2.24 Å) and that of II contains the coordinated tolane molecule and the oxygen atom of the terminal trimethylacetate ligand (NbO 2.16, NbC 2.18 and 2.19, CC 1.29 Å, PhCC angles 141 and 146°). An unusually large splitting of OCO stretching frequencies is observed in the IR spectrum of I (1652?1305 = 347 cm^?1). Structural characteristics of the coordinated CC triple bond in II are similar to those found in Cp(π-Ph₄C₄)Nb(CO)(π-Ph₂C₂) studied earlier. The role played by the Nb^III lone pair in I and II is discussed.     

Nanostructured cathodic catalysts for direct methanol fuel cells

The high activity of catalysts based of nanodisperse Pt-P system and their tolerance to the poisoning effect of methanol are demonstrated for the working potentials of cathodes in methanol-air fuel cells. The catalysts’ activity in the oxygen reduction reaction in the presence of methanol is nearly hundred times that of catalysts based on mixed metal-chalcogenide systems.     

Formation of Pt-S-Mn groups in platinum triphenylphosphine complexes with cymanthrenylthiolate ligands

Stepwise decarbonylation of the platinum complex with cymanthrenylthiolate ligands cis-(Ph₃P)₂Pt[(SC₅H₄)Mn(CO)₃]₂ (1) affords the cis-(Ph₃P)₂Pt[(SC₅H₄)Mn(CO)₃]-[(SC₅H₄)Mn(CO)₂] (2) and cis-(Ph₃P)₂Pt[(SC₅H₄)Mn(CO)₂]₂ (3) complexes. The replacement of one carbonyl group at the manganese atom with the lone electron pair of sulfur is accompanied by the formation of a new Mn-S bond giving rise to an unusual norbornane-type core. Complexes 1–3 were characterized by elemental analysis and IR spectroscopy. The structures of complexes 1–3 were established by single-crystal X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1508–1512, July, 2005.