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Isonicotinamide as entering ligand on trans-[Ru(NH3)4P(OR)3(H2O)]22+, (R = Me, Pr, iPr and Bu)

1986; Elsevier BV; Volume: 113; Issue: 1 Linguagem: Inglês

10.1016/s0020-1693(00)86858-9

1873-3255

José Cardoso do Nascimento Filho, Douglas Wagner Franco,

Lanthanide and Transition Metal Complexes

trans-[Ru(NH3)4P(OR)3(H2O)]2+ (R = Me, Pr, iPr, and Bu) reacts with isonicotinamide at second-order- specific rates k1 of 1.2, 2.3, 7.4 and 8.1 M−1 s−(25 °C, μ = 0.10 NaCF3COO/CH3COOH), respectively, for R = Me, Pr, iPr and Bu. The products trans- [Ru(NH3)4P(OR)3isn](PF6)2 have been isolated and characterized by micro analysis, cyclic voltammetry, and electronic spectral data. The aquation rates k−1 for the isonicotinamide (isn) derivatives are 5.2 × 10−2, 5.9 × 10−2, 2.0 × 10−1 and 3.4 × 10−1 s−1 for R= Me, Pf, Bu and iPr, respectively. The activation parameters for the forward and backward reactions indicate the same mechanism for all of them. The substitution proceeds by a dissociative mechanism with a significant outer-sphere association of trans-[Ru(NH3)4P(OR)3(H2O)]2+ complexes with isn. Assuming k1 as indicative of the lability of the coordinated water molecule on the monophosphite complexes, the following sequence of increasing trans-effect mav be proposed: P(OMe)3 <P(OEt)3 <P(OPr)3 <P(OiPr)3 <P(OBu)3. The affinity of the monophosphite complexes for isn increases according to P(OMe)3 ⋍ P(OiPr)3 < P(OEt)3 < P(OPr)3 ⋍ P(OBu)3.