Breher Frank, Rüegger Heinz, Mlakar Marina, Rudolph Manfred, Deblon Stephan, Schönberg Hartmut, Boulmaâz Souad, Thomaier Jörg, Grützmacher Hansjörg
Department of Chemistry and Applied Biology, ETH Hönggerberg, Wolfgang-Pauli Str. 8093 Zürich, Switzerland.
Chemistry. 2004 Feb 6;10(3):641-53. doi: 10.1002/chem.200305116.
The formation of adducts of the square-planar 16-electron complexes trans-M(tropp(ph))(2) and cis-M(tropp(ph))(2) (M=Rh, Ir; tropp(Ph)=5-diphenylphosphanyldibenzo[a,d]cycloheptene) with acetonitrile (acn) and Cl(-), and the redox chemistry of these complexes was investigated by various physical methods (NMR and UV-visible spectroscopy, square-wave voltammetry), in order to obtain some fundamental thermodynamic and kinetic data for these systems. A trans/cis isomerization cannot be detected for M(tropp(ph))(2) in non-coordinating solvents. However, both isomers are connected through equilibria of the type trans-M(tropp(ph))(2)+L<==>ML(tropp(ph))(2)<==>cis-M(tropp(ph))(2)+L, involving five-coordinate intermediates ML(tropp(ph))(2) (L=acn, n=+1; L=Cl(-), n=0). Values for K(d) (K(f)), that is, the dissociation (formation) equilibrium constant, and k(d) (k(f)), that is, the dissociation (formation) rate constant, were obtained. The formation reactions are fast, especially with the trans isomers (k(f)>1x10(5) m(-1) s(-1)). The reaction with the sterically more hindered cis isomers is at least one order of magnitude slower. The stability of the five-coordinate complexes ML(tropp(ph))(2) increases with Ir>Rh and Cl(-)>acn. The dissociation reaction has a pronounced influence on the square-wave (SW) voltammograms of trans/cis-Ir(tropp(ph))(2). With the help of the thermodynamic and kinetic data independently determined by other physical means, these reactions could be simulated and allowed the setting up of a reaction sequence. Examination of the data obtained showed that the trans/cis isomerization is a process with a low activation barrier for the four-coordinate 17-electron complexes M(tropp(ph))(2) and especially that a disproportionation reaction 2 trans/cis-M(tropp(ph))(2)-->M(tropp(ph))(2)+M(tropp(ph))(2) may be sufficiently fast to mask the true reactivity of the paramagnetic species, which are probably less reactive than their diamagnetic equilibrium partners.
研究了平面正方形16电子配合物反式-[M(tropp(ph))(2)]⁺和顺式-[M(tropp(ph))(2)]⁺（M = Rh、Ir；tropp(Ph)=5-二苯基膦基二苯并[a,d]环庚烯）与乙腈（acn）和Cl⁻形成加合物的过程，以及这些配合物的氧化还原化学，采用了多种物理方法（核磁共振和紫外可见光谱、方波伏安法），以便获得这些体系的一些基本热力学和动力学数据。在非配位溶剂中，无法检测到[M(tropp(ph))(2)]⁺的反式/顺式异构化。然而，两种异构体通过反式-[M(tropp(ph))(2)]⁺ + L⇌[ML(tropp(ph))(2)]ⁿ⇌顺式-[M(tropp(ph))(2)]⁺ + L类型的平衡相互关联，涉及五配位中间体[ML(tropp(ph))(2)]ⁿ（L = acn，n = +1；L = Cl⁻，n = 0）。获得了K(d)（K(f)）的值，即解离（形成）平衡常数，以及k(d)（k(f)）的值，即解离（形成）速率常数。形成反应很快，尤其是对于反式异构体（k(f)>1×10⁵ m⁻¹ s⁻¹）。与空间位阻更大的顺式异构体的反应至少慢一个数量级。五配位配合物[ML(tropp(ph))(2)]ⁿ的稳定性随着Ir>Rh以及Cl⁻>acn而增加。解离反应对反式/顺式-[Ir(tropp(ph))(2)]⁺的方波伏安图有显著影响。借助其他物理方法独立测定的热力学和动力学数据，可以模拟这些反应并建立反应序列。对所得数据的研究表明，对于四配位17电子配合物[M(tropp(ph))(2)]⁰，反式/顺式异构化是一个活化能垒较低的过程，特别是歧化反应2反式/顺式-[M(tropp(ph))(2)]⁰→[M(tropp(ph))(2)]⁺ + [M(tropp(ph))(2)]⁻可能足够快，从而掩盖了顺磁性物种的真实反应性，顺磁性物种的反应性可能比其抗磁性平衡伙伴低。
