10.1021/acs.inorgchem.7b01868.s001 Luis M. Martínez-Prieto Luis M. Martínez-Prieto Pilar Palma Pilar Palma Eleuterio Álvarez Eleuterio Álvarez Juan Cámpora Juan Cámpora Nickel Pincer Complexes with Frequent Aliphatic Alkoxo Ligands [(<sup>iPr</sup>PCP)Ni-OR] (R = Et, <i>n</i>Bu, <i>i</i>Pr, 2‑hydroxyethyl). An Assessment of the Hydrolytic Stability of Nickel and Palladium Alkoxides American Chemical Society 2017 parent alcohol ROH ligand i Pr CH 2 CH 2 OH equilibrium acidic hydroxide series PCP Pd Et covalent Ni-OR bonds Nickel Pincer Complexes nickel pincer complexes NMR hydrolysis constant X-ray diffraction data iPr heteroatom-free R groups 2- methoxyethoxide complexes Ni alkoxide complexes n Bu 2017-10-06 15:49:26 Journal contribution https://acs.figshare.com/articles/journal_contribution/Nickel_Pincer_Complexes_with_Frequent_Aliphatic_Alkoxo_Ligands_sup_iPr_sup_PCP_Ni-OR_R_Et_i_n_i_Bu_i_i_i_Pr_2_hydroxyethyl_An_Assessment_of_the_Hydrolytic_Stability_of_Nickel_and_Palladium_Alkoxides/5478622 A series of nickel pincer complexes with terminal alkoxo ligands [(<sup>iPr</sup>PCP)­Ni-OR] (R = Et, <i>n</i>Bu, <i>i</i>Pr, CH<sub>2</sub>CH<sub>2</sub>OH; <sup>iPr</sup>PCP is the 2,6-bis­(diisopropylphosphinomethyl)­phenyl pincer ligand) was synthesized and fully characterized. Together with the previously reported methoxo analogues of Ni and Pd, these complexes constitute a unique series of isostructural late transition-metal alkoxides. Spectroscopic and X-ray diffraction data provide direct indications of the strong polarization of their covalent Ni-OR bonds. One of the most salient features of this class of compounds is their facile hydrolysis with traces of moisture, leading to equilibrium mixtures with the corresponding hydroxides [(<sup>iPr</sup>PCP)­M–OH] (M = Ni or Pd) and alcohols, ROH. To compare the hydrolytic stability of nickel and palladium alkoxides, we performed NMR titrations of both hydroxides with several alcohols and determined the corresponding equilibrium constants. In general, these constants are ca. 1 order of magnitude smaller for M = Ni than Pd, indicating that Ni alkoxide complexes are more readily hydrolyzed than their Pd counterparts. For alkoxide complexes containing heteroatom-free R groups, the tendency to hydrolyze decreases as the parent alcohol ROH becomes more acidic, that is, R = Me > Et > <i>i</i>Pr. This intuitive trend is broken for 2-methoxyethanol, the most acidic alcohol investigated. The hydroxo/2-methoxyethanol exchange equilibrium constants are comparable to those of ethanol (M = Ni) or methanol (M = Pd), showing that the corresponding 2-methoxyethoxide complexes are more prone to hydrolysis than anticipated. These experimental observations were rationalized in the light of density functional theory calculations.