Kinetics of hydrolysis of di-µ-hydroxo-bis[nitrilotriacetatocobaltate(III)] to diaqua(nitrilotriacetato)cobalt(III), and some reactions of the latter with non-metallic substrates in aqueous solution

Abstract

Kinetics of Hydrolysis of Di-p-hydroxo-bis[nitrilotriacetatocobaltate-( III)] t o Diaqua(nitrilotriacetato)cobalt(iii), and some Reactions of the latter with Non-metallic Substrates in Aqueous Solution

The role of hydroxo-bridged dinuclear species and the influence of “innocent” buffers in the reactivity of cis-[CoIII(cyclen)(H2O)2]3+ and [CoIII(tren)(H2O)2]3+ complexes with biologically relevant ligands at physiological pH

“…Similarly, when the solution obtained after 24 h at 50 °C is acidified to 1 M HClO 4 , the UV-Vis and 13 C NMR spectra of the cis-[Co(cyclen)(H 2 O) 2 ] 3+ species are obtained after 1 hour at room temperature. The formation of [{cis-Co(cyclen)} 2 (μ-OH) 2 ] 4+ dimeric units from the previous [{cis-Co(cyclen)(H 2 O)} 2 (μ-OH)] 5+ species 35,43,53 (see before) fully agrees both with the spectroscopic, pH and kinetic profiles associated with this slower process (24 h, 50 °C). It is also very relevant to indicate that leaching of Co III or cyclen to the medium is prevented during the entire process (Fig.…”

Preparation, structure, and interconversion kinetics of mono- and binuclear aquo(nitrilotriacetato)cobaltate(III) complexes

“…Returning to the fast reaction data, inspection shows that simple second-order kinetics does not apply, contrary to the previous suggestion based on very limited data. 3 We have found the best fit to be attained by use of an equation of the M"' s -\Kl =42.8 M'1. dk2 = 0.131 M"' s'1, Jf, =91 '1.…”

“…Activity has recently intensified due to the demonstration of highly anisotropic electrical conduction in some of these materials. 3 We expect compounds of the type described herein…”

“…The structural proposals have also been questioned on the basis of NMR data2 and conventional chemical evidence. 3 It now appears that Mori et al's a-K[Co(NTA)-(OH)(OH2)] species is in fact binuclear2 and is probably of the form already mentioned,3 that their /?-K[Co(NTA)-(OH)(OH2)] does have the formula assigned but may be impure, 3 and that what they identified as a binuclear complex is in fact the species3 K[Co(HNTA)2]-2H20 (HNTA represents the monoprotonated triply coordinating form of NTA).…”

Theoretical study on dinitrogen complexes. Position of the third protonation and the reduction mechanism

“…Complexes attached by one or two protons are considered to be intermediates of the reduction.2 The features of proton- order to produce the reduction products from diprotonated complexes (N2H2), further protonation is needed at the terminal nitrogen (NT) or that attached to the central metal (NA). Takahashi et al found that the third proton attacks the central metal to form a seven-coordinate intermediate.4 5 They proposed the fourth protonation to reduce the protonated N2 ligand. Chatt et al, on the other hand, expected for NH3 formation that the fourth protonation occurred at NT, following the attack of the third protonation at NA.6 They also considered that the NHNH2 complex was likely to be an intermediate along the route of N2H4 formation.3 It is, therefore, the key to the reduction where the protonation occurs in the N2H2 complex.…”