Czap Almut, Heinemann Frank W, van Eldik Rudi
Institute for Inorganic Chemistry, University of Erlangen-Nürnberg, Egerlandstr. 1, 91058 Erlangen, Germany.
Inorg Chem. 2004 Nov 29;43(24):7832-43. doi: 10.1021/ic0350685.
The kinetics of the unusually fast reaction of cis- and trans-[Ru(terpy)(NH3)2Cl]2+ (with respect to NH3; terpy=2,2':6',2"-terpyridine) with NO was studied in acidic aqueous solution. The multistep reaction pathway observed for both isomers includes a rapid and reversible formation of an intermediate Ru(III)-NO complex in the first reaction step, for which the rate and activation parameters are in good agreement with an associative substitution behavior of the Ru(III) center (cis isomer, k1=618 +/- 2 M(-1) s(-1), DeltaH(++) = 38 +/- 3 kJ mol(-1), DeltaS(++) = -63 +/- 8 J K(-1) mol(-1), DeltaV(++) = -17.5 +/- 0.8 cm3 mol(-1); k -1 = 0.097 +/- 0.001 s(-1), DeltaH(++) = 27 +/- 8 kJ mol(-1), DeltaS(++) = -173 +/- 28 J K(-1) mol(-1), DeltaV(++) = -17.6 +/- 0.5 cm3 mol(-1); trans isomer, k1 = 1637 +/- 11 M(-1) s(-1), DeltaH(++) = 34 +/- 3 kJ mol(-1), DeltaS(++) = -69 +/-11 J K(-1) mol(-1), DeltaV(++) = -20 +/- 2 cm3 mol(-1); k(-1)=0.47 +/- 0.08 s(-1), DeltaH(++)=39 +/- 5 kJ mol(-1), DeltaS(++) = -121 +/-18 J K(-1) mol(-1), DeltaV(++) = -18.5 +/- 0.4 cm3 mol(-1) at 25 degrees C). The subsequent electron transfer step to form Ru(II)-NO+ occurs spontaneously for the trans isomer, followed by a slow nitrosyl to nitrite conversion, whereas for the cis isomer the reduction of the Ru(III) center is induced by the coordination of an additional NO molecule (cis isomer, k2=51.3 +/- 0.3 M(-1) s(-1), DeltaH(++) = 46 +/- 2 kJ mol(-1), DeltaS(++) = -69 +/- 5 J K(-1) mol(-1), DeltaV(++) = -22.6 +/- 0.2 cm3 mol(-1) at 45 degrees C). The final reaction step involves a slow aquation process for both isomers, which is interpreted in terms of a dissociative substitution mechanism (cis isomer, DeltaV(++) = +23.5 +/- 1.2 cm3 mol(-1); trans isomer, DeltaV(++) = +20.9 +/- 0.4 cm3 mol(-1) at 55 degrees C) that produces two different reaction products, viz. [Ru(terpy)(NH3)(H2O)NO]3+ (product of the cis isomer) and trans-[Ru(terpy)(NH3)2(H2O)]2+. The pi-acceptor properties of the tridentate N-donor chelate (terpy) predominantly control the overall reaction pattern.
在酸性水溶液中研究了顺式和反式-[Ru(terpy)(NH₃)₂Cl]²⁺（相对于NH₃；terpy = 2,2':6',2"-三联吡啶）与NO异常快速反应的动力学。观察到的两种异构体的多步反应途径包括在第一步中快速且可逆地形成中间体Ru(III)-NO配合物，其速率和活化参数与Ru(III)中心的缔合取代行为高度一致（顺式异构体，k₁ = 618 ± 2 M⁻¹ s⁻¹，ΔH⁺⁺ = 38 ± 3 kJ mol⁻¹，ΔS⁺⁺ = -63 ± 8 J K⁻¹ mol⁻¹，ΔV⁺⁺ = -17.5 ± 0.8 cm³ mol⁻¹；k⁻¹ = 0.097 ± 0.001 s⁻¹，ΔH⁺⁺ = 27 ± 8 kJ mol⁻¹，ΔS⁺⁺ = -173 ± 28 J K⁻¹ mol⁻¹，ΔV⁺⁺ = -17.6 ± 0.5 cm³ mol⁻¹；反式异构体，k₁ = 1637 ± 11 M⁻¹ s⁻¹，ΔH⁺⁺ = 34 ± 3 kJ mol⁻¹，ΔS⁺⁺ = -69 ± 11 J K⁻¹ mol⁻¹，ΔV⁺⁺ = -20 ± 2 cm³ mol⁻¹；k⁻¹ = 0.47 ± 0.08 s⁻¹，ΔH⁺⁺ = 39 ± 5 kJ mol⁻¹，ΔS⁺⁺ = -121 ± 18 J K⁻¹ mol⁻¹，ΔV⁺⁺ = -18.5 ± 0.4 cm³ mol⁻¹，25℃）。随后形成Ru(II)-NO⁺的电子转移步骤对反式异构体是自发进行的，接着是缓慢的亚硝酰基向亚硝酸盐的转化，而对于顺式异构体，Ru(III)中心的还原是由另一个NO分子的配位诱导的（顺式异构体，k₂ = 51.3 ± 0.3 M⁻¹ s⁻¹，ΔH⁺⁺ = 46 ± 2 kJ mol⁻¹，ΔS⁺⁺ = -69 ± 5 J K⁻¹ mol⁻¹，ΔV⁺⁺ = -22.6 ± 0.2 cm³ mol⁻¹，45℃）。最终反应步骤涉及两种异构体的缓慢水合过程，这根据解离取代机理来解释（顺式异构体，ΔV⁺⁺ = +23.5 ± 1.2 cm³ mol⁻¹；反式异构体，ΔV⁺⁺ = +20.9 ± 0.4 cm³ mol⁻¹，55℃），该过程产生两种不同的反应产物，即[Ru(terpy)(NH₃)(H₂O)NO]³⁺（顺式异构体的产物）和反式-[Ru(terpy)(NH₃)₂(H₂O)]²⁺。三齿N供体螯合物（terpy）的π受体性质主要控制整个反应模式。
