Hydroxide water clusters

Similar thermal effects have also been noted in hydroxide water clusters [54]. While proton transfer is widely accepted to follow the "Grotthuss" mechanism... 

Men CJ, Tao FM (2007) Hydration and dissociation of calcium hydroxide in water clusters a quantum chemical study. J Theor Comput Chem 6 595-609... 

However, while ruthenium carbonyl was found to decompose the formate ion in basic media, the rate was slower (<0.1 mmol trimethyl ammonium formate to H2 and C02 per hour) than the rate of the water-gas shift reaction (>0.4 mmol H2/hr) at 5 atm CO and 100 °C. Increasing CO pressure decreased the formate decomposition rate. However, it was observed that increasing the CO pressure from 5 atm CO to 50 atm increased the H2 production rate to 10 mmol/hr. They proposed, in a similar manner to Pettit et al.,34 a mechanism that involved nucleophilic attack by amine (instead of hydroxide). Activation of the metal carbonyl (e.g., Ru3(CO) 2 cluster to Ru(CO)5) was suggested to be favored by dilution, increases in CO pressure, or, in the case of Group VIb metal carbonyl complexes, photolytic promotion. The mechanism is shown below in Scheme 9 ... 

They based this modification on the known adsorbance of OH on glass and on the common occurrence of transition metal mixed water-ammonia complexes with coordination number of 4. Parallel stractural studies of the deposited CdS showed textured growth, supporting a mechanism whereby alternate Cd and S species were involved, in an ion-by-ion process. Such a growth suggests adsorption of a molecular hydroxy-ammine species rather than a cluster. In fact, the mechanism of Ortega-Borges and Lincot also does not differentiate between a hydroxide cluster and molecule. 

Ge(OH)+, Ge(OH)2+, Ge(OH)3+ and Ge202+, etc. It is clear from these observations that atoms tends to form clusters in thin films. Thin films also tend to react with water in the atmosphere. In field evaporation, water molecules are desorbed in the form of hydride, oxide or hydroxide ions with the substrate atoms and atomic clusters. From the above discussions, it is clear that the FIM and atom-probe can now be applied to study a wide variety of problems for a wide variety of materials. Field ion microscopy is no longer confined to studying refractory metals, as many scientists still erroneously perceive. 

Initial attack of hydroxide ions onto Ni(CO)4 gives as yet uncharacterized species,1 which readily condense with unreacted Ni(CO)4 to give variable mixtures of [Ni5(CO)12]2- and [Ni6(CO)12]2-. Hydrolysis of [Ni5(CO)12]2- in water produces [Ni6(CO)12]2-, according to the above reaction. The dianion [Ni CO) 2]2- is isolated as the tetramethylam-monium salt in a crystalline state in 70% yield. The [Ni6(CO)12]2 dianion is a starting material for the synthesis of several other homo- and heteromet-allic nickel carbonyl cluster complexes.1-9... 

Barium hydroxide octahydrate, Ba(OH)2 8 H20, is a crystalline compound that contains eight water molecules clustered around the barium atom. We ll learn more about hydrates in Section 14.15. 

A mechanism for the oxidation of carbon monoxide at cluster C has been proposed [139] in it CO and water bind to the cluster (Figure 6a). By analogy with cyanide binding, water is proposed to bind to the high-spin Ni(II) and CO to an iron atom of the cluster. After dehydronation of the water molecule the resulting hydroxide attacks the CO to form -COOH. Dehydronation of this spe-... 

In urease, the active site with a pair of nickel ions is unique. A large number of esterases and phosphatases contain dinuclear clusters of zinc and/or iron, and in these a metal-bound hydroxide or water molecule is a common feature [170], In urease the active site is rather rigid and designed to favor binding of urea over that of solvent water, and for this purpose nickel may be preferable to zinc, which has more flexible coordination geometry. 

Ln E, clusters are air-sensitive, a definite obstacle in composite materials synthesis. Air-stable O-containing ligands (e.g. O2-) could be another solution but the resulting clusters react with water to form hydroxides. Selenium oxide is an alternative soluble source of oxo ligands, giving for instance [Ln8(/u,3-0)2(M5-Se)2(SePh)i6(thf)8]-6thf clusters (fig. 101, bot-... 

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