Synthesis and Characterization of New Ammine Ru(II) Complexes Containing P(m-tol)3, P(p-CH3)3 and P(OC5H11)3

Journal of the Brazilian Chemical Society

Universidade Federal do Ceará, Fortaleza, Brazil¹  Universidade de São Paulo, São Carlos, Brazil¹  Mazzetto, Selma E.¹  Signini, Roberta¹ 

关键词: ruthenium(II);    ammine complexes;    phosphine and phosphite ligands;   

DOI  :  10.1590/S0103-50532002000500017

学科分类：化学（综合）

来源: SciELO

【 摘 要 】

Phosphorus compounds are important ancillary ligands in the art of tailoring catalysts. Their presence in the metal coordination sphere can introduce significant changes in the kinetic and thermodynamic properties of metal complexes containing these ligands. The chemistry of phosphine and phosphite complexes of Ru(II) and Ru(III) tetraammines has received considerable attention,1-11 efforts being directed to the understanding of the trans effect and trans influence of these ligands in the thermal1-11 and photochemical12-17 reactivities of the ruthenium center the complex itself. According to the accumulated data,1-11 for small phosphines and phosphites effect and trans influence are dictated mainly by electronic effects.1 In this work, the attention was focused on the reactions with the following bulky phosphorus ligands L = P(m-tol)3 (θ=170o), P(p-tol)3 (θ=145o) and P(OC5H11)3 (θ=170o). The basicity of these ligands does not change substantially from one another as do their sizes and therefore the influence of these ligands on the properties of [Ru(NH3)4(L)(H2O)]2+ complex ions would be primarily due to steric rather than electronic effects.   Experimental Chemicals and reagents The solvents employed were freshly distilled before use. Doubly distilled water was used throughout. All chemicals were of analytical grade purity. The syntheses of the ruthenium compounds, [Ru(NH3)5Cl]Cl2, [Ru(NH3)5(H2O)](PF6) 2 followed the procedures already described.18,19 Ruthenium trichloride (RuCl3.3H2O) was the starting material for the synthesis of the ruthenium complexes. Apparatus and techniques All manipulations were performed under argon due to the known sensitivity of Ru(II) complexes to air oxidation. The complexes were stored under vacuum and protected from light. Their purity was checked by means of elemental analysis, cyclic voltammetry and spectrophotometric measurements. Elemental analyses were performed by the staff of the Microanalytical Laboratory of Instituto de Química-USP. The UV-VIS spectra were recorded on a HP 8451A-diode array spectrophotometer with 1.0 cm quartz cells at room temperature. Kinetic studies were carried out under pseudo-first-order conditions and were monitored by following the changes in absorbance at a selected wavelength. Cyclic voltammetric measurements were performed in a multifunctional PARC system consisting of a model 175 Universal Programmer a model 173 potentiostat-galvanostat, a model 379 digital coulometer, a model 376 voltage-current conversor and a model Re 0074 X-Y recorder. For cyclic voltammetric measurements a glassy carbon electrode, platinum wire and SCE were used as the working, auxiliary and reference electrodes, respectively. Formal reduction potentials for a number of substituted ruthenium ammine complexes were evaluated by cyclic voltammetry. The E1/2 values were taken as the average of the anodic and cathodic peak potentials. Electrochemical reversibility was judged by (a) comparing the ratio of the peak current for the cathodic process relative to the peak current for the anodic process20,21 and (b) comparing under the same conditions the peak to peak separation with that of trans-[Ru(NH3)4P(OC2H 5)3H2O]2+ known to be reversible.1 The electrochemical process in acidic solution is reversible in the sense that the oxidation and reduction wave currents are equal.20-21 The peak to peak separation, 60±5 mV, is of the same magnitude observed for others ammine Ru(II) complexes systems1 which are also know to be reversible. Kinetic measurements The reaction shown in equation 1 was monitored both by potentiometric (pH) and spectrophotometric (λmax= 380 nm) measurements. In the

【 授权许可】

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