5
82
BEREZIN, TOLDINA
[
ZnAc (HAc) ] and [ëÓAc (HAc) ] by Py, DMSO, and of mixed solvate as compared to the individual one. In
2 4 2 4
2
98
individual solvent, the degree of solvation of the tran-
sition state decreases in the series of the solvents
–
1 –1
DMF are reported in [9]: k (l mol s ) are equal to
v
2+
2+
2
6.8, 18.8, 14.2 (Zn ) and 0.478, 0.199, 0.71 (ëÓ ),
DMF > Py > DMSO. The kinetic compensation effect
#
respectively. One can see that the series of the rates of
(
E = a + b∆S ) brings about the statistic average
2
+
substitution changes when going from Zn (Py > growth in the activation energy in the binary solvents
2
+
DMSO > DMF) to Co (DMF > Py > DMSO). In addi- (for example, in DMSO–Py, E = 69 kJ/mol > (70 +
tion, the difference in the rates of substitution is low 55)/2 kJ/mol). In the case of the H íêíÇê reaction
2
2
+
#
in the case of Zn and is substantially higher for with ZnAc , values ∆S and E in the binary system of
2
–1 –1
2
+
solvents (–57 J (mol K ) and 63 kJ/mol) are also
somewhat higher than the statistic average values in
pure DMSO and DMF (–60 J (mol K ) and
1 kJ/mol). Obviously, the metal ion is coordinatively
more saturated in the binary electron-donor solvents.
Co , which can be explained also by the trans-effect
in the Co(II) complexes. As was previously shown,
the reaction of formation of the metal analog of chlo-
rophyll from Co(II) salts in the presence of ethanol is
catalyzed by urea and thiourea, salicylic acid [10],
–
1
–1
6
dialkylsulfide, carbon disulfide and CO [11], imid-
2
azole [12].
ACKNOWLEDGMENTS
The trans-effect in Cu(II) complexes was previously
mentioned in [13–16]. The development of the trans-
effect in Cu(II) complexes was suggested in [14] during
the kinetic study of Cu(II) chlorophyll formation from
We are grateful to E.V. Kudrik (assistant professor,
Ivanovo State University of Chemical Technology) for
providing tetraphenyltetrabenzoporphine reagent and
to Foundation for Assistance to Domestic Science for
financial support.
ëuAc in the HAc–acetone mixture. It was found that
2
the reaction is noticeably catalyzed by acetone. The
(
ëç ) ë=é molecule has π orbitals and can form π-
3
2
2+
backbonds with Cu , which is a sufficient condition for
REFERENCES
the efficient trans-effect in the coordination sphere of
1
2
. Berezin, B.D., Koord. Khim., 1993, vol. 19, no. 5, p. 358.
2
+
2+
2+
the ëu complex. The trans-effect in Cu and Co is
suggested to appear at the stage of formation of the
transition state of reaction (2) that is stabilized by the
coordinated acetone [9].
. Grinberg, A.A., Vvedenie v khimiyu kompleksnykh
soedinenii (Introduction to the Chemistry of Complex
Compounds), Moscow: Goskhimizdat, 1951, p. 295.
. Yatsimirskii, K.B., Termokhimiya kompleksnykh
soedinenii (Thermochemistry of Complex Compounds),
Moscow: Akad Nauk SSSR, 1951, p. 111.
. Bersuker, I.B. and Ablov, A.V., Khimicheskaya svyaz’ v
kompleksnykh soedineniyakh (Chemical Bond in Com-
plex Compounds), Chisinau: Shtiintsa, 1962, p. 150.
5. Kukushkin, Yu.N., Khimiya koordinatsionnykh soedine-
nii (The Chemistry of Coordination Compounds), Mos-
cow: Vysshaya Shkola, 1985, p. 184.
3
4
While estimating the contribution of the trans-effect
to the reactivity of complex solvates using the indicator
reaction of metal porphyrinate formation (2), one
should account for specific properties of porphyrin as a
ligand (ç ê). This work revealed more extended range
2
of the ç ê structural types that can be used as “indica-
2
tors” of the trans-effect.
Recently, porphyrins are classified as ligands with
the localized and active NH bond, as classic and
uncommon ç ê [17]. The latter exhibit NH-activity in
6. Luk’yanets, E.A., Dashkevich, S.N., and Kobayashi, N.,
Zh. Obshch. Khim., 1993, vol. 63, no. 6, p. 1411.
2
the electron-donor solvents and therefore, in such
media, reactions (1) and (2) can be also catalyzed due
to this reason. We previously showed [18, 19] that
7. Gordon, A.J. and Ford, R.A., The Chemist’s Companion:
A Handbook of Practical Data, Techniques and Refer-
ences, New York: Wiley, 1972.
8. Berezin, B.D., Koordinatsionnye soedineniya porfirinov
i ftalotsianina (Coordination Compounds of Porphyrins
and Phthalocyanine), Moscow: Nauka, 1978.
. Berezin, B.D. and Golubchikov, O.A., Koordinatsion-
naya khimiya sol’vatokompleksov solei perekhodnykh
metallov (Coordination Chemistry of Solvation Com-
plexes Formed by Transition-Metal Salts), Moscow:
Nauka, 1992.
0. Volkova, N.I., Karavaeva, E.B., and Berezin, B.D., Zh.
Neorg. Khim., 1975, vol. 20, no. 7, p. 1929.
ç íêíÇê occupies an intermediate position between
2
classic and uncommon ç ê ligands and can show NH-
2
activity in the electron-donor media only [19]. The
9
contribution of NH-activation to the k value for
v
ç íêíÇê in DMSO, Py, and DMF is minimum,
2
which is confirmed by close k values in these sol-
v
vents.
The other feature of ç íêíÇê is its nonplanar
2
1
1
structure [20]. This is one of the reasons for its higher
reactivity with respect to the metal salts and allows one
to use it in the indicator reaction (2), which is more con-
1. Volkova, N.I., Karavaeva, E.B., and Berezin, B.D., Izv.
Vyssh. Uchebn. Zaved., Khim. Khim. Tekhnol., 1976,
vol. 19, no. 12, p. 1859.
venient as compared to the classic ç ê.
2
The data in the table show that more positive acti- 12. Berezin, B.D., Volkova, N.I., and Karavaeva, E.B., Zh.
#
vation entropies (∆S ) of the process are characteristic
of the binary solvents. This is likely to be explained by 13. Berezin, B.D. and Klopova, L.V., Zh. Fiz. Khim., 1977,
more profound solvation of the salt in the composition
vol. 51, no. 9, p. 2157.
Neorg. Khim., 1977, vol. 22, no. 2, p. 405.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 30 No. 8 2004