The influence of the boat-to-chair conversion on the demetallation of the nickel(II) complex of an open-chain tetramine containing a piperazine fragment.
The nickel(II) complex with an open chain tetramine containing a piperazine fragment (1) displays an unusual resistance to demetallation in acidic solution and exhibits a lifetime of about five minutes in a solution 0.1 M in HClO4 and 7.0 M in NaClO4. Sluggishness with respect to the demetallation is ascribed to the occurrence of the boat-to-chair conformational conversion of the piperazine fragment, which implies the passage through the highly energetic half-boat transition state. The use of a high concentration of the inert electrolyte induces a 'salting out' effect on both thermodynamics (stability of metal complexes is enhanced) and kinetics (resistance to demetallation is increased).
Boiocchi
Massimo
M
Centro Grandi Strumenti, Università di Pavia, 27100 Pavia, Italy.
Bonizzoni
Marco
M
Fabbrizzi
Luigi
L
Foti
Francesco
F
Licchelli
Maurizio
M
Taglietti
Angelo
A
Zema
Michele
M
D001952:Bridged-Ring Compounds / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D000077489:Piperazine; D010879:Piperazines / Q000737:chemistry*
D001952:Bridged-Ring Compounds; D009942:Organometallic Compounds; D010879:Piperazines; D000077489:Piperazine; D009532:Nickel; C010349:tetramethylenedisulfotetramine