Basallote Manuel G, Feliz Marta, Fernández-Trujillo M Jesús, Llusar Rosa, Safont Vicent S, Uriel Santiago
Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, Facultad de Ciencias, Universidad de Cádiz, Apartado 40, Puerto Real, 11510 Cádiz, Spain.
Chemistry. 2004 Mar 19;10(6):1463-71. doi: 10.1002/chem.200305376.
The cluster W(3)S(4)H(3)(dmpe)(3) (1) (dmpe=1,2-bis(dimethylphosphino)ethane) reacts with HX (X=Cl, Br) to form the corresponding W(3)S(4)X(3)(dmpe)(3) (2) complexes, but no reaction is observed when 1 is treated with an excess of halide salts. Kinetic studies indicate that the hydride 1 reacts with HX in MeCN and MeCN-H(2)O mixtures to form 2 in three kinetically distinguishable steps. In the initial step, the W-H bonds are attacked by the acid to form an unstable dihydrogen species that releases H(2) and yields a coordinatively unsaturated intermediate. This intermediate adds a solvent molecule (second step) and then replaces the coordinated solvent with X(-) (third step). The kinetic results show that the first step is faster with HCl than with solvated H(+). This indicates that the rate of protonation of this metal hydride is determined not only by reorganization of the electron density at the M-H bonds but also by breakage of the H-X or H(+)-solvent bonds. It also indicates that the latter process can be more important in determining the rate of protonation.
簇合物W(3)S(4)H(3)(dmpe)(3)（1）（dmpe = 1,2 - 双（二甲基膦基）乙烷）与HX（X = Cl、Br）反应形成相应的W(3)S(4)X(3)(dmpe)(3)（2）配合物，但当用过量卤化物盐处理1时未观察到反应。动力学研究表明，氢化物1在乙腈和乙腈 - H(2)O混合物中与HX反应，通过三个动力学上可区分的步骤形成2。在第一步中，W - H键被酸攻击形成不稳定的二氢物种，该物种释放H(2)并产生配位不饱和中间体。该中间体添加一个溶剂分子（第二步），然后用X(-)取代配位的溶剂（第三步）。动力学结果表明，第一步中HCl比溶剂化的H(+)更快。这表明该金属氢化物的质子化速率不仅取决于M - H键处电子密度的重新排列，还取决于H - X或H(+) - 溶剂键的断裂。这也表明后一过程在确定质子化速率方面可能更重要。
