Kinetics of phosphine substitution in CpRu(PPh3)2X (X = Cl, Br, I, N3, and NCO)
Kinetics of phosphine substitution in CpRu(PPh3)2X (X = Cl, Br, I, N3, and NCO)
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DOI：
10.1039/c7ra02793a
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发表时间：
2017-01-01
期刊：
影响因子：
3.9
通讯作者：
Kirss, Rein U.
中科院分区：
文献类型：
--
作者：
Hill, David;Delaney, Connor;Kirss, Rein U.
在准一级反应条件下，测定了CpRu（PPh 3）（2）X（X = Br，1b，X = I，1c，X = N-3，1d，X = NCO，1 e）在THF溶液中的膦取代反应动力学，并与CpRu（PPh 3）（2）X（1a）的数据进行了比较.相对取代率为1a > 1d > 1b > 1 e> 1c。取代率下降的存在下，添加PPh 3和独立的添加X与解离过程一致。1a-1c的活化参数（Δ H-匕首= 113-135 kJ mol（-1），Δ S 21-102 J mol（-1）K-1）和DFT计算支持解离或解离交换途径，即使在1d-e中观察到负活化熵（Δ S-匕首= -48 +/- 16至-105 +/- 5 J mol（-1）K-1）。Ru-配体键角的差异在1d-e点不同的π-受体性质的拟卤化物配体，有助于更快的速率取代的叠氮化物配合物，1d相对于氰酸酯衍生物1 e。当X = F，1f，X = H，1g，X = SnF 3，1h或X = SnCl 3，1 i时，未观察到取代。化合物1b-1 e也与氯仿反应得到1a。卤化物交换的速率与1c和1d的膦取代相当。后一种反应被过量的三苯基膦抑制，不受自由基抑制剂和自由基陷阱的影响，这表明自由基机制是不可能的。
The kinetics of phosphine substitution in CpRu(PPh3)(2)X (X = Br, 1b, X = I, 1c, X = N-3, 1d, and X = NCO, 1e) have been measured under pseudo-first order conditions in THF solution and compared with data for CpRu(PPh3)(2)X (1a). The relative rate of substitution is found to be 1a > 1d > 1b > 1e > 1c. Substitution rates decrease in the presence of added PPh3 and are independent of added X consistent with a dissociative process. Activation parameters for 1a-1c (Delta H-dagger = 113-135 kJ mol(-1), Delta S 21-102 J mol(-1) K-1) and DFT calculations support a dissociative or dissociative interchange pathway even though negative activation entropies (Delta S-dagger = -48 +/- 16 to -105 +/- 5 J mol(-1) K-1) are observed for 1d-e. Differences in Ru-ligand bond angles in 1d-e point to different pi-acceptor properties of the pseudohalide ligands, contributing to the faster rate of substitution for the azide complexes, 1d relative to the cyanate derivative 1e. Substitution is not observed when X = F, 1f, X = H, 1g, X = SnF3, 1h, or X = SnCl3, 1i. Compounds 1b-1e also react with chloroform to yield 1a. The rates of halide exchange are comparable to phosphine substitution for 1c and 1d. The latter reaction is inhibited by excess triphenylphosphine and is unaffected by both radical inhibitors and radical traps suggesting that a radical mechanism is unlikely.