| Abstract
| - The influence of two different di(1-pyrazolyl)alkane ligands on the rate constant of aqua ligandsubstitution of ruthenium(II) complexes with the formula [Ru(H2O)(L2)(tpmm)]2+ (L2 = di(1-pyrazolyl)methane(DPMet) or 2,2-di(1-pyrazolyl)propane (DPPro)) was investigated. A 9.4 × 105-fold increase in the rate constantof ligand substitution at pH = 6.86 was observed when DPMet was replaced with DPPro. This remarkableincrease was unexpected, considering that these bidentate ligands appear quite similar. To help lend insightinto this dramatic spectator ligand effect, the activation parameters for the ligand substitution reactions weredetermined, and single-crystal X-ray data were collected on the structurally analogous (chloro)ruthenium(II)complexes, [Ru(Cl)(L2)(tpmm)]+. These results are discussed in the context of a heteroscorpionate effect exertedby the DPPro ligand.
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