Shaban SAEFY, Heinemann FW, van Eldik R (2009)
Publication Status: Published
Publication Type: Journal article
Publication year: 2009
Publisher: WILEY-BLACKWELL
Pages Range: 3111-3118
Journal Issue: 21
The synthesis, structure and ligand substitution mechanism of a new five-coordinate copper(II) complex with a sterically constrained pytBuN(3) chelate ligand [pytBuN(3) = 2,6-bis(3,5di-tert-butylphenyhminomethyl)pyridine] are reported. In the crystal structure of the complex the [Cu(pytBuN(3))Cl-2] chromophore possesses a distorted trigonal-bipyramidal coordination geometry. The kinetics and mechanism of chloride substitution by thiourea (TU) and N,N,N',N'-tetramethylthiourea (TMTU) were studied in detail as a function of nucleophile concentration, temperature and pressure in methanol as solvent. The kinetics showed that the substitution reaction of [Cu(pytBuN(3))Cl-2] is a biphasic process that involves the subsequent displacement of both chloride ligands. The substitution of the first chloride by TU, k(1)(296) = 918 +/- 30 M-1 s(-1), is 570 times faster than the substitution of the second chloride, k(2)(296) = 1.62 +/- 0.06 M-1 s(-1). Substitution of chloride by TU is characterized by the activation parameters: Delta H-# = 42 2 and 58 +/- 2 kJmol(-1), Delta S-# = -46 +/- 7 and -47 +/- 6 J K(-1)mol(-1), and Delta V-# = -6.5 +/- 0.2 and -5.3 +/- 0.7 cm(3)mol(-1), for the first and second substitution reactions, respectively. It is concluded from the activation parameters that both reactions follow an associative interchange (I-a) mechanism. When the substitution reaction was carried out with the sterically hindered nucleophile TMTU, the rate constant for the displacement of the first chloride, k(2)(296) = 6.9 +/- 0.5 M-1 s(-1), was more than 133 times slower than for the reaction with TU, which further supports the I-a nature of the substitution mechanism. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
APA:
Shaban, S.A.E.F.Y., Heinemann, F.W., & van Eldik, R. (2009). A New Trigonal-Bipyramidal [Cu-II(pytBuN(3))Cl-2] Complex: Synthesis, Structure and Ligand Substitution Behaviour. European Journal of Inorganic Chemistry, 21, 3111-3118. https://doi.org/10.1002/ejic.200900302
MLA:
Shaban, Shaban Abd El Fattah Youssef, Frank Wilhelm Heinemann, and Rudi van Eldik. "A New Trigonal-Bipyramidal [Cu-II(pytBuN(3))Cl-2] Complex: Synthesis, Structure and Ligand Substitution Behaviour." European Journal of Inorganic Chemistry 21 (2009): 3111-3118.
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