ISSN:
1572-901X
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract A series of complexes of stoichiometry [MX2(dipyS)] {dipyS = bis(2–picolyl)-1,3–dithiopropane); M=Cr, Mn, Fe, Co, Ni, X=Cl; M=Ni or Cu, X=NO3} and [VOCl(dipyS)]Cl have been prepared and characterised, including the X-ray crystal structure of [Ni(ONO2)2(dipyS)]. The kinetics of the transfer of dipyS from these complexes (M=Cr, Mn, Fe, Co or Ni) to Cu2+, to form [Cu(dipyS)]2+, have been studied in MeOH. For M=Ni, the kinetics are consistent with a mechanism involving rate-limiting dissociation of the initial pyridyl—M bond. Subsequent binding of Cu2+ to the pendant pyridyl-residue (or binding Cl− to the vacant site on M) is followed by the complete transfer of dipyS from M to Cu. For M=Cr, Mn or Co, the same mechanism is believed to operate, but in these cases intermediates in the dipyS transfer to Cu2+ have been detected spectroscopically. Evidence is presented that these intermediates have Cu2+ bound to a pendant pyridyl-group on [MCl2(dipyS)] and that the subsequent complete transfer of dipyS involves rate-limiting dissociation of a M—S bond. For M=Fe, e.p.r. spectroscopy shows that the complex is a dimer in solution. However, the transfer reaction with Cu2+ involves an analogous intermediate to that with M=Cr, Mn or Co, but only at high concentrations of Cu2+. Unexpectedly, the binding of Cu2+ inhibits the transfer of dipyS from Fe to Cu. The electronic factors which give rise to this behaviour are discussed.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1023/A:1006983218095
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