Hydroxo bridges

The oxide (p. 1209), chalcogenides (p. 1210) and halides (p. 1211) have already been described. Of them, the only ionic compound is HgF2 but other compounds in which there is appreciable charge separation are the hydrated salts of strong oxoacids, e.g. the nitrate, perchlorate, and sulfate. In aqueous solution such salts are extensively hydrolysed (HgO is only very weakly basic) and they require acidification to prevent the formation of polynuclear hydroxo-bridged species or the precipitation of basic salts such as Hg(OH)(N03) which contains infinite zigzag chains ... 

The general reluctance of reagents to reduce O2 in one-equivalent states is further exemplified in the cases of V(II) and Cr(II). Autoxidation of V(1I), ultimately to V(III), produces ° an intermediate dimer, VOV ", identified spectrally and a known product of the reaction between V(II) and Clearly one path involves an initial two-equivalent oxidation of V(ri) to V(IV) and Swinehart ° calculates that 60 % of the oxidation follows this route. Cr(Il) perchlorate produces a species containing two Cr(III) species linked by one 0x0-or two hydroxo-bridges and Cr(lV) is proposed as the first intermediate F... 

Adventitious water is responsible for the formation of the dimeric hydroxo complex 31 obtained by reaction of AuCb with 1,4-dilithiotetraphenylbutadiene in ether solution [97[. The hydroxo-bridged complex [Au(C6H4N02-2)2( i-0H)[2 (32) was obtained either by reaction of Na[Au(C6H4N02-2)2(0Ph)2] with traces of water in CH2Cl2/n-hexane solution or by treatment of the dichloroaurated complex with NaOH [98[. The crystal structure of 32 2Et20 shows that it is a centrosymmetric... 

The hydroxo complexes [Au(6-Rbipy)(OH)2], postulated as intermediates in the formation of 44c-i, are not isolated nevertheless, in all the mass spectra (FAB conditions) a weak peak is found corresponding to these species. Unchanged 44c-i are quantitatively recovered from the reaction with aqueous solutions of HX (X = BF4 or PFfi) neither dihydroxo complexes similar to those observed in the vapor phase, nor hydroxo bridged dimers are obtained [25]. 

In strongly basic solution this reaction involves the formation of an hydroxo bridge in addition to the dioxygen bridge 43). The redox potential for the process... 

It has been noted (84) that U-dioxygen (type 1) complexes formed in solution often contain a u-hydroxo bridge, in addition to the /i-dioxygen bridge, provided that each cobalt atom has a vacant coordination site. Fig. 4 illustrates the dibridged M-(02, OH)—M moitey... 

Bimetallic zinc complexes formed with hexaazamacrocycles were studied in the hydrolysis of activated carboxyesters. Potentiometric titration demonstrated the dominant presence of a dinuclear hydroxo bridged species at pH >7. /)-Nitrophenyl acetate is hydrolyzed with no loss of catalytic activity for at least 2.7 catalytic cycles 4... 

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