Hydroxo groups

Merola reported the preparation of hydrido(carboxylato)iridium(lll) complexes, mer-[lrCl(0C(0)R)(H)(PMe3)3] (90) (R = Ph, Me), by oxidative addition of acetic acid or benzoic acid to [Ir(cod)(PMe3)3]Cl (67) [46]. The structure of 90 (R = Ph) in which the carboxylato ligand coordinates as an T -ligand, was confirmed by X-ray analysis. The reaction of 67 with salicylic acid yielded the product 91, which resulted from activation of the O-H bond of the carboxylato but not of the hydroxo group (Scheme 6-13). 

The constants given for reactions (v), (vi) and (vii) are representative of those of a ligand containing a carboxylic acid and a phenolic hydroxo group. 

Abstracting from the complexity of the real systems, there is one common property of all natural particles. Their surfaces contain functional groups which can interact with H+, OH and metal ions and - if Lewis acid sites, e.g., =AI and =Fe, are available on the surface - with ligands. Many inorganic solids (oxidesQand silicates) contain hydroxo groups carbonates and sulfides expose -C-oh,-c oh, MeOH and -SH groups, respectively. While the interaction of alkaline and earth-alkaline ions... 

The complex undergoes in dichloromethane solution a partially reversible single oxidation (E° = —0.25 V, vs. SCE), assigned as a one-electron process. This result would support the access to the corresponding mixed-valent Fe(II)Fe(III) species, the partial reversibility of the process having been attributed to deprotonation of the -hydroxo group.35... 

There is evidence that in the oxidized form, an oxo or hydroxo group bridges the Ni and Fe atoms, which should be absent in the enzymatically active reduced form. 

The solubility of organic acids in water is due to the hydrophilic 0x0- and hydroxo-groups of the acid that form hydrogen bonds with water molecules. If the hydrogen ion of the acid is solvated by a donor organic base, B, in the... 

This approach emphasizes the role of water as a source of 0X0 ligands. It is important to note that crystalline tetranuclear 4B and undecanuclear 11 aggregates form only if the amounts and concentrations of water vary within certain narrow limits. Perhaps the number of potentially bridging oxo and hydroxo groups that can form in solution determine the nuclearity of the aggregates. 

Recently, Sargeson s group has studied the hydration of coordinated carboxy-alkoies as model chemistry for the aconitase reaction (61). A key feature of their nxrdel is the activation of the double bond via carboxylate coordination to the metal and subsequent attack by a coordinated cu-hydroxo group. This was a feature of the "ferrous wheel mechanism as well. The model chemistry suggested that a closer examination of carboxyl labeled substrate and substrate analogues was... 

A class of ligands which is very flexible in terms of its denticity, donor atom geometry, and steric demands are Schiff bases derived from salicyladehyde or related carbonyl compounds carrying additional hydroxo groups. The use of bi- and tridentate ligands of this type allows the synthesis of mixed-chelate complexes with a number of O N, N N or N S bidentate ligands. The products are of considerable interest for nuclear medical applications as well as for homo-... 

The salts were at first described by Jorgensen as aquo-salts, as they are formed from aeido-nitro-salts by the action of dilute aqueous ammonia but this was contradicted by Werner, who showed that they contain a hydroxo-group in the nucleus.4... 

In this series of compounds one of the hydroxo-groups of the bridged linking is much more easily split off than the other, hence they readily pass into the diaquo-hexammino-p-amino-ol-dicobaltic salts. For example, if the nitrate is crystallised from water containing nitric acid, the hydroxo linkage is broken and the substance passes into the diaquo-p.-amino-olsalt thus ... 

A series of compomids has been prepared containing a hydroxo-group in place of an acidic group in the pentaminino-platinic compounds. These have general formula [Pt(NH3)sOH]R3. 

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