Geometry oxalic acid

The direct reaction of [TCO4] in ethanolic solution with dppe and oxalic acid produces the red Tc" complex [Tc(ox)(dppe)2] (552). Attempts to prepare similar complexes with succinic acid, phthalic acid, or salicylic acid failed, or the complexes were stable in solution only. " Similarly, cationic complexes of Tc" are produced by reaction of the versatile precursor [TcO(OH)(dppe)2] (204) with various dithiocarbamates, which produces several complexes of general formula [Tc(dtc)(dppe)2] (553). For this reaction the reductant formamidine sulphinic acid (510) was required in an alkaline solution. The X-ray crystal structure of [Tc(S2CNMe2)(dppe)2] (554) shows a distorted octahedral geometry. Cyclic voltammetry reveals a reversible reduction wave Tc"/Tc couple at —0.53 V, and a reversible oxidation at +0.3 V for the Tc" /Tc" couple. The same compound (554) was also prepared from the thiourea precursor [TcO(tmtu)4] + (91).The reaction of this precursor in dmf in the presence of dppe produced a mixture of brown [TcO(dtc)(tmtu)2] and the Tc" complex (553). The first compound is probably an intermediate... 

Table 2.4. Hydrogen bond geometry in the a- and / -deutero oxalic acid dideuterates from neutron diffraction analysis [83]...

Oxalic acid test 100gH2C204-H20 + 900 mL H20 Anodically etched at 1 A/cm2for 1.5 min Geometry of attack on polished surface at 250 x or 500 x + 1.70 to 2.0 or greater Various carbides... 

Usually aqueous solutions of Cr(V) are very unstable and undergo rapid disproportionation to Cr(Vl) and Cr(III) However, Rocek and coworkers " have shown that oxalic acid and glycolic acid combine with Gr(V) to form relatively stable complexes. These same workers have more recently shown that 2-hydroxy-2-methylbutyric add and dtric add form Cr(V) complexes sufihdently stable to permit storage of aqueous solutions of Cr(V) for extended periods of time (up to several weeks if stored frozen at -20°C) . In further work they have been able to obtain crystals of potassium bis(2-hydroxy-2-methylbutyrate)oxochromate(V) monohydrate and to determine its crystal structure The geometry of e complex was intermediate between square pyramidal and trigonal bipyramidal. The ability of oxalic add to form a stable complex with Cr(V) enables this compound to catalyze some Cr(VI) oxidations Square pyramidal complexes of oxalic add and Cr(V) have been proposed on the basis of EPR studies ... 

Oxalic acid etch t lOOg H2C2O4 Anodically etched at 1. Geometry of attack -1- 1-70 to + 2 00 or Various carbides H... 

Scheme 12 While the binding of diols by trigonal boronic acids can be considered almost negligible, this is not the case when boronic acids complex with more acidic poly-hydroxyl species. Here the complexation of trigonalphenylboronic acid with oxalic acid proceeds with a rate constant kcooHcooH of 2000 s With trigonal boron acids complexation is generally discussed in terms of the overall reaction proceeding with a change in geometry from trigonal to tetrahedral at boron on complexation.

Scheme 13 The transition state proposed by Pizer was considered associative with the intermediate complex being tetrahedral. In this transition state it was suggested that proton transfer from the entering ligand (here, the oxalic acid on the right) to the leaving hydroxyl (the proton acceptor) could be ratedetermining (for clarity the mobile proton is indicated in bold red). One caveat for the proposed transition state was that the interconversion between trigonal and tetrahedral geometries should be rapid, as in the addition of OH to B(OH) 3, which had been previously assumed to be diffusion controlled ...

Quasi-ID Nanostructures. A porous membrane with cylindrical pore geometry can be used as a template for the synthesis of quasi-ID nanostruetures, which was pioneered by Martin. Anodic aluminum oxide (AAO) films can be produced upon by anodie oxidation of aluminum foil in an eleetrolyte, typically of sulfuric, phosphoric, chromic, or oxalic acids. The AAO film contains hexagonally packed nanopores, perpendicular to the AAO membrane surface, uniform in diameter. Using them as template, highly ordered and vertically aligned nanowire arrays can be electrochemical produced. 

The IR and Raman spectra of Cr(pic)3, where Hpic = 2-picolinic acid, include vCrN at 305 cm-1 and vCrO at 379/364 cm-1 (IR), 357 cm-1 (Raman).159 The complex Cr(N)(quin)2, where quin = 8-hydroxo-quinolinate, gives an IR band at 1015 cm-1, as expected for vCr=N in a five-coordinate complex.160 Skeletal mode assignments were proposed, from the IR and Raman spectra of [Cr(ox)(cyclam)]+, where ox = oxalate, cyclam = 1,4,8, 11-tetra-azacyclotetradecane. These were consistent with the presence of bidentate oxalate, and a cis-V geometry for the cyclam ligand.161... 

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