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Kinetics and Mechanism Study of the Substitution Reactions of the Chloride Ligand in Dichloro(5,10,15,20)‐tetraphenyl‐21 H ,23 H ‐porphinato)tin(IV) by Organic Bases in Dimethylformamide Solvent
Author(s) -
Asadi Mozaffar,
Mohammadi Khosro,
Zebardasti Abedien
Publication year - 2002
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(200209)85:9<2975::aid-hlca2975>3.0.co;2-1
Subject(s) - chemistry , ligand (biochemistry) , butylamine , reaction rate constant , medicinal chemistry , stereochemistry , kinetics , organic chemistry , amine gas treating , receptor , biochemistry , physics , quantum mechanics
Substitution reactions of a Cl − ligand in [SnCl 2 (tpp)] (tpp=5,10,15,20‐tetraphenyl‐21 H ,23 H ‐porphinato(2−)) by five organic bases i.e. , butylamine (BuNH 2 ), sec ‐butylamine ( s BuNH 2 ), tert ‐butylamine ( t BuNH 2 ), dibutylamine (Bu 2 NH), and tributylamine (Bu 3 N), as entering nucleophile in dimethylformamide at I =0.1 M (NaNO 3 ) and 30–55° were studied. The second‐order rate constants for the substitution of a Cl − ligand were found to be (36.86±1.14)⋅10 −3 , (32.91±0.79)⋅10 −3 , (22.21±0.58)⋅10 −3 , (19.09±0.66)⋅10 −3 , and (1.36±0.08)⋅10 −3 M −1 s −1 at 40° for BuNH 2 , t BuNH 2 , s BuNH 2 , Bu 2 NH, and Bu 3 N, respectively. In a temperature‐dependence study, the activation parameters Δ H ≠ and Δ S ≠ for the reaction of [SnCl 2 (tpp)] with the organic bases were determined as 38.61±4.79 kJ mol −1 and −150.40±15.46 J K −1 mol −1 for BuNH 2 , 40.95±4.79 kJ mol −1 and −143.75±15.46 J K −1 mol −1 for t BuNH 2 , 30.88±2.43 kJ mol −1 and −179.00±7.82 J K −1 mol −1 for s BuNH 2 , 26.56±2.97 kJ mol −1 and −194.05±9.39 J K −1 mol −1 for Bu 2 NH, and 39.37±2.25 kJ mol −1 and −174.68±7.07 J K −1 mol −1 for Bu 3 N. From the linear rate dependence on the concentration of the bases, the span of k 2 values, and the large negative values of the activation entropy, an associative (A) mechanism is deduced for the ligand substitution.