Algarra Andrés G, Basallote Manuel G, Fernandez-Trujillo M Jesús, Llusar Rosa, Safont Vicent S, Vicent Cristian
Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorganica, Facultad de Ciencias, Universidad de Cadiz, Apartado 40, Puerto Real, 11510 Cadiz, Spain.
Inorg Chem. 2006 Jul 24;45(15):5774-84. doi: 10.1021/ic0520770.
The 1H,19F HOESY spectra of the title compounds in CD2Cl2 solution indicate that the cluster cations form ion pairs with the BF4- and PF6- anions with a well-defined interionic structure that appears to be basically determined essentially by the nature of the X- ligand. For the clusters with X = H and OH, the structure of the ion pairs is such that the counteranion (Y-) and the X- ligands are placed close to each other. However, when the size and electron density of X- increase (X = Br), Y- is forced to move to a different site, far away from X-. The relevance of ion-pairing on the chemistry of these compounds is clearly seen through a decrease in the rate of proton transfer from HCl to the hydride cluster [W3S4H3(dmpe)3]+ in the presence of an excess of BF4-. The kinetic data for this reaction can be rationalized by considering that the ([W3S4H3(dmpe)3]+, BF4-) ion pairs are unproductive in the proton-transfer process. Theoretical calculations indicate that the real behavior can be more complex. Although the cluster can still form adducts with HCl in the presence of BF4-, the structures of the most-stable BF4--containing HCl adducts show H...H distances too large to allow the subsequent release of H2. In addition, the effective concentration of HCl is also reduced because of the formation of adducts as ClH...BF4-. As a consequence of both effects, the proton transfer takes place more slowly than for the case of the dihydrogen-bonded HCl adduct resulting from the unpaired cluster.
标题化合物在CD2Cl2溶液中的1H、19F HOESY光谱表明，簇阳离子与BF4-和PF6-阴离子形成离子对，具有明确的离子间结构，该结构似乎基本上由X-配体的性质决定。对于X = H和OH的簇，离子对的结构使得抗衡阴离子（Y-）和X-配体彼此靠近放置。然而，当X-的尺寸和电子密度增加时（X = Br），Y-被迫移动到远离X-的不同位置。通过在过量BF4-存在下，从HCl到氢化物簇[W3S4H3(dmpe)3]+的质子转移速率降低，可以清楚地看出离子配对对这些化合物化学性质的影响。该反应的动力学数据可以通过考虑（[W3S4H3(dmpe)3]+，BF4-）离子对在质子转移过程中无活性来合理化。理论计算表明，实际行为可能更复杂。尽管在BF4-存在下簇仍可与HCl形成加合物，但最稳定的含BF4-的HCl加合物的结构显示H...H距离太大，无法随后释放H2。此外，由于形成加合物ClH...BF4-，HCl的有效浓度也降低。由于这两种效应，质子转移比由未配对簇形成的二氢键合HCl加合物的情况进行得更慢。
