Platinum alkoxides

Insertion reactions involving metal alkoxides are also known. For example, carbon dioxide is known to react with some metal alkoxides as shown in equation (12). The formation of a bidentate ligand is a significant thermodynamic driving force for some of these reactions. The isoelectronic aryl and alkyl isocyanates and carbodiimides can react similarly. Insertion reactions involving alkenes and carbon monoxide are known for platinum alkoxides. 

This two-electron oxidation of an alcohol occurs with a concomitant two-electron reduction of PtCli to PtCl4, although prolonged photolysis leads to complete reduction to platinum metal. The initial quantum yield for PtCli" disappearance is 4 times greater than the initial PtCl4 appearance quantum yield, which is consistent with the equilibrium formation of PtCls by the condisproportionation of PtCli and PtCli . The aldehyde and ketone likely arise from a ) -hydrogen transfer reaction from an intermediate platinum alkoxide complex/ ... 

Reactive halogens in various series have been removed by catalytic hydrogenation with either platinum or palladium catalysts, and other nucleophiles which have been used in chloride displacements include hydroxide ion, alkoxides, hydrosulflde, hydrazine and toluene-p-sulfonylhydrazine, and trimethyl phosphite. 

Tin, nitratodiphenyltris(dimethy) sulfoxide)-structure, 1,77 Tin, nitratotris(triphenyltin)-structure, 1, 47 Tin,tetrakis(acetato)-stereochemistry, 1,94 Tin, tetrakis(diethyldithiocarbamato)-angular parameters, 1, 57 Tin, tetrakis(ethyldithiocarbamato)-angular parameters, 1, 57 Tin, tetranitrato-stereochemistry, 1, 94 Tin, tri-n-butylmethoxy-, 3, 208 Tin alkoxides physical properties, 2, 346 Tin bromide, 3, 194 Tin bromide hydrate, 3,195 Tin carboxylates, 3, 222 mixed valence, 3, 222 Tin chloride, 3, 194 hydroformylation platinum complexes, 6, 263 Tin chloride dihydrate, 3,195 Tin complexes, 3, 183-223 acetyl ace tone... 

DNA polymerases, 5, 1007 Trans effect, 1,16, 26, 315 metal complexes, 2, 705, palladium(II) amine complexes, 5, 1115 platinum complexes, 5, 353, 493 six-coordinate compounds. 1, 49 T ransestcrification metal alkoxide synthesis, 2, 340 Transferases zinc, S, 1002... 

The synthesis of precursors A and B (see Figure 12.10) has been described by Michalczyk et al. [102]. These compounds can be synthesised from platinum-catalysed hydrosilylation reactions, that is addition reactions between Si—H and C=C groups in the presence of a catalyst. Once the pure precursors are obtained, BSG can be synthesised by incorporation of calcium alkoxide during polycondensation of the precursors. 

R.R. Schrock, M.I.T. Have you or anyone else prepared platinum(IV) metallacyclobutane complexes with alkoxide ligands in place of chlorides One might expect the alkoxide complexes to behave considerably differently than the chloro complexes, perhaps like early transition metal complexes. 

The most usual synthetic routes to the derivatives of platinum group metals are the exchange reactions of the complexes containing halide ligands with alkali metal alkoxides (method 5), alcoholysis of the same kind derivatives (usually by phenols, method 4), alcoholysis of hydroxide complexes (method 3), and redox reactions — reduction of chlorides or 0s04 in alcohol media (method 7) (Table 12.25). 

The molecular derivatives of platinum group metals are usually rather well soluble in organic solvents and volatile in vacuum. At normal pressure they demonstrate very low thermal stability and easily decompose producing fine metal powders. This decomposition occurs more easily for the derivatives of branched radicals as it is based on a P-hydrogen elimination process. An important feature of the chemical behavior of these alkoxide complexes is their rather high stability to hydrolysis. Some derivatives can even form outer sphere hydrates when reacted with water in organic solvents. This stability to hydrolysis can at least partially be due to the kinetic inertness of the complexes of this group. 

As many other derivatives of the platinum metals the alkoxide ones find... 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

Preparation of metal oxide thin film by means of stepwise absorption of metal alkoxide has been carried out in the past for the activation of heterogeneous catalysts [13]. For example, Asakura et al. prepared one-atomic layer of niobium oxide by repeating chemisorption of Nb(OEt)5 on silica beads. The catalyst obtained by immobilizing platinum particles on a niobum oxide layer showed improved reactivity for hydrogenation of ethylene in comparison with... 

In addition to catalyzing hydroformylation, the platinum SPO complexes are excellent hydrogenation catalysts for aldehydes (as already demonstrated by the side products of hydroformylation), in particular, in the absence of carbon monoxide. Further, in ibis process, the facile heterolytic splitting of dihydrogen may play a role. The hydrogenation of aldehydes requires the presence of carboxylic acids, and perhaps the release of alkoxides from platinum requires a more reactive proton donor than that available on the nearby SPO. For example, 4 hydrogenates 2-methylpropanal at 95 °C and 40 bar of H2 to give the alcohol, with a TOF of 9000 mol moN h (71). 

Aqua ions are known but not very stable. Substitution of Pt in aqueous solution is sometimes zero-order in the added ligand, L, or can have both L-dependent and L-independent contributions to the rate, probably because intermediate formation of an unstable aqua complex is the rate-determining step for the L-independent pathway. A large number of O-donors, particularly anionic ones, give stable complexes, for example, carbonate, acetate, oxalate, acetylacetonate, and alkoxide. Tetrameric platinum(II) acetate is formed by formic acid reduction of Pt solutions in acetic acid. It does not appear to be a very useful synthetic precursor for Pt chemistry. The acetylacetonate [Pt(acac)2] is monomeric and square planar. 

M. Niwa, K. Kawashima, and Y. Murakami, A Shape-Selective Platinum-Loaded Mordenite Catalyst for the Hydrocracking of Paraffins by the Chemical Vapour Deposition of Silicon Alkoxide. J. Chem. Soc., Faraday Trans. 1, 1985, 81, 2757-2761. 

---