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Zinc Thiolate Complexes [ZnL n (SR)] + with Azamacrocyclic Ligands, Part II: Mechanism of the Reaction with CS 2
Author(s) -
Notni Johannes,
Schenk Stephan,
Roth Arne,
Plass Winfried,
Görls Helmar,
Uhlemann Ute,
Walter Angela,
Schmitt Michael,
Popp Jürgen,
Chatzipapadopoulos Susana,
Emmler Thomas,
Breitzke Hergen,
Leppert Jörg,
Buntkowsky Gerd,
Kempe Kristian,
Anders Ernst
Publication year - 2006
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200500948
Subject(s) - chemistry , crystallography , stereochemistry , reaction rate constant , activation energy , orthorhombic crystal system , monoclinic crystal system , associative substitution , zinc , medicinal chemistry , kinetics , crystal structure , biochemistry , physics , organic chemistry , quantum mechanics , catalysis
The thiolate complexes [Zn([15]aneN 4 )(S–CH 2 –C 6 H 5 )]ClO 4 ( 1 ) ([15]aneN 4 = 1,4,8,12‐tetraazacyclopentadecane) and [Zn( i ‐[14]aneN 4 )(S–CH 2 –C 6 H 5 )]ClO 4 ( 2 ) ( i ‐[14]aneN 4 = 1,4,7,11‐tetraazacyclotetradecane) have been reacted with carbon disulfide. The trithiocarbonate complexes [Zn([15]aneN 4 ){S–C(S)–S–CH 2 –C 6 H 5 }]ClO 4 { 1a , monoclinic, space group P 2 1 / n , Z = 8, a = 13.2338(1) Å, b = 12.9251(2) Å, c = 30.1669(4) Å, β = 101.463(1)°, V = 5057.1(1) Å 3 } and [Zn( i ‐[14]aneN 4 ){S–C(S)–S–CH 2 –C 6 H 5 }]ClO 4 { 2a , orthorhombic, space group P 2 1 2 1 2 1 , Z = 8, a = 9.9936(1) Å, b = 22.1261(4) Å, c = 22.3192(4) Å, V = 4935.2(1) Å 3 } were obtained. The reaction of 1 with CS 2 is second order with a rate constant of k = (57.6 ± 2.4) × 10 –3 M –1 · s –1 at 25 °C. The experimentally determined Eyring activation barrier is Δ H exp ‡ = 65.3 ± 0.7 kJ · mol –1 (Δ S exp ‡ = –49.9 ± 2.5 J · mol –1 · K –1 ) and a free energy of activation of Δ G ‡ = 80.2 ± 1.5 kJ · mol –1 at 25 °C. To discriminate between an associative and a dissociative mechanism the barriers for both processes were calculated using density functional theory at the C‐PCM(B98/G3MP2Large)//B3LYP/6‐311+G(d) level. The associative mechanism is clearly favored with a difference in free energies of activation of δ Δ G ‡ ≈ 80 kJ · mol –1 . Its calculated barrier Δ G theor ‡ = 114.3 kJ · mol –1 is in reasonable agreement with the experimental value. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)