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Substitution reactions of some pseudo-halides in trans -[Ru(NH 3 )P(OEt) 3 (H 2 O)] 2+

1987; NRC Research Press; Volume: 65; Issue: 2 Linguagem: Inglês

10.1139/v87-063

1480-3291

Sonia Maria Neiva, Lucídio Souza Santos, Sebastião Barros Araújo, José Cardoso do Nascimento Filho, Douglas Wagner Franco,

Chemical Reaction Mechanisms

The kinetics and mechanism of the formation of trans-[Ru(NH 3 ) 4 P(OEt) 3 X] 1+ (X = SCN − , CN − , and[Formula: see text]) have been investigated. The second order specific rate constants k 1 for the substitution of the water molecule in trans-[Ru(NH 3 ) 4 P(OEt) 3 (H 2 O)] 2+ for CN − , [Formula: see text], and SCN − are (3.1 ± 0.3) × 10 2 , (1.7 ± 0.1) × 10 2 , and (1.4 ± 0.1) × 10 2 M −1 s −1 , respectively, at 25 °C, μ = 1.0 (NaCF 3 COO). Under the same experimental conditions the aquation of the pseudohalide derivatives, trans-[Ru(NH 3 ) 4 P(OEt) 3 X] + proceeds at specific rates of (1.8 ± 0.1) × 10 and (2.8 ± 0.1) × 10 −1 s −1 for X = [Formula: see text] and SCN − , respectively, and the upper limit for the rate of CN − loss from trans-[Ru(NH 3 ) 4 P(OEt) 3 CN] + was estimated as 1.2 × 10 −1 s −1 . The order of affinities for the monophosphite complex in the series of ligands studied is:[Formula: see text]where imN = imidazol, pyr = pyrazine, and Mepyr + = methylpyrazinium. From enthalpies of activation it is possible to estimate that net replacement of H 2 O in trans-[Ru(NH 3 ) 4 P(OEt) 3 (H 2 O)] 2+ by azide ions is exothermic by 2.8 ± 2 kcal/mol.