Blazina Damir, Dunne John P, Aiken Stuart, Duckett Simon B, Elkington Charlotte, McGrady John E, Poli Rinaldo, Walton Sue J, Anwar M Sabieh, Jones Jonathan A, Carteret Hilary A
Department of Chemistry, University of York, Heslington, York, UKYO10 5DD.
Dalton Trans. 2006 May 7(17):2072-80. doi: 10.1039/b510616h. Epub 2006 Feb 2.
The synthesis, characterisation and thermal and photochemical reactivity of Ru(CO)2(PPh3)(dppe) 1 towards hydrogen are described. Compound proved to exist in both fac (major) and mer forms in solution. Under thermal conditions, PPh3 is lost from 1 in the major reaction pathway and the known complex Ru(CO)2(dppe)(H)2 2 is formed. Photochemically, CO loss is the dominant process, leading to the alternative dihydride Ru(CO)(PPh3)(dppe)(H)2 3. The major isomer of 3, viz. 3a, contains hydride ligands that are trans to CO and trans to one of the phosphorus atoms of the dppe ligand but a second isomer, 3b, where both hydride ligands are trans to distinct phosphines, is also formed. On the NMR timescale, no interconversion of 3a and 3b was observed, although hydride site interchange is evident with activation parameters of DeltaH(double dagger) = 95 +/- 6 kJ mol(-1) and DeltaS(double dagger) = 26 +/- 17 J K(-1) mol(-1). Density functional theory confirms that the observed species are the most stable isomeric forms, and suggests that hydride exchange occurs via a transition state featuring an eta2-coordinated H2 unit.
描述了Ru(CO)2(PPh3)(dppe) 1与氢气的合成、表征以及热反应和光化学反应。该化合物在溶液中被证明以面式（主要）和经式两种形式存在。在热条件下，主要反应途径中PPh3从1中失去，形成已知的配合物Ru(CO)2(dppe)(H)2 2。在光化学条件下，CO的损失是主要过程，导致生成另一种二氢化物Ru(CO)(PPh3)(dppe)(H)2 3。3的主要异构体，即3a，其氢化物配体与CO以及与dppe配体的一个磷原子呈反式，但也形成了第二种异构体3b，其中两个氢化物配体都与不同的膦呈反式。在核磁共振时间尺度上，未观察到3a和3b之间的相互转化，尽管氢化物位点交换明显，其活化参数为ΔH‡ = 95 ± 6 kJ mol-1和ΔS‡ = 26 ± 17 J K-1 mol-1。密度泛函理论证实所观察到的物种是最稳定的异构体形式，并表明氢化物交换通过具有η2配位H2单元的过渡态发生。
