Step complex formation in the dichloro(5,10,15,20-tetraphenylporphinate)hafnium(IV)-pyridine-toluene system

The thermodynamic characteristics and kinetics of step reactions between dichloro(5,10,15,20-tetraphenylporphinate)hafnium(IV) (Cl)(2)HfTPP and a "small" organic base, pyridine (Py), in toluene were studied. The coordination of the Py molecule (K (1) = 1.50 x 10(4) l/mol) was determined. The slow irreversible displacement of Cl- in (Cl)(2)(Py)HfTPP into the second coordination sphere (k (1) = 9.74 x 10(-4) s(-1)), the substitution of the second Py molecule for Cl- in (Cl)(2)(Py)HfTPP (K-2 = 14.15 l/mol), subsequent irreversible displacement of the second Cl- ion into the outer sphere (k(2) = 6.05 x 10(-4) s(-1)), and the coordination of the third Py molecule as a result of the replacement of Cl- with the formation of [(Py)(3)HfTPP](2+) center dot 2Cl(-) (K-3 = 0.23 l/mol) at the first, second, and third stages, respectively, were observed. Prospects for the use of the metalloporphyrin as a receptor of organic N-bases were considered.