1394791-96-8Relevant articles and documents
POCOP-Type Pincer Complexes of Nickel: Synthesis, Characterization, and Ligand Exchange Reactivities of New Cationic Acetonitrile Adducts
Lapointe, Sbastien,Vabre, Boris,Zargarian, Davit
, p. 3520 - 3531 (2015)
This report describes the synthesis, characterization, and ligand exchange studies of a family of cationic acetonitrile adducts of nickel featuring resorcinol-based, pincer-type POCOP ligands. The compounds [(R-POCOPR′)Ni(NCMe)][OSO2CF3] (R-POCOPR′ = 2,6-(R′2PO)2(RnC6H3-n); R′ = i-Pr: R = H (1), p-Me (2), p-OMe (3), p-CO2Me (4), p-Br (5), m,m-t-Bu2 (6), m-OMe (7), m-CO2Me (8); R′ = t-Bu: R = H (9), p-CO2Me (10)) were prepared in 80-93% yields by reacting the corresponding charge-neutral bromo derivatives with Ag(OSO2CF3) in acetonitrile. The impact of the R- and R′-substituents on electronics and structures of 1-10 have been probed by NMR, UV-vis, and IR spectra, X-ray crystallography, and cyclic voltammetry measurements. The observed ν(C≡N) values were found to increase with the increasing electron-withdrawing nature of R, i.e., in the order 7 2C-substituted cations showed the highest oxidation potentials. Moreover, all cationic adducts showed greater oxidation potentials compared with their corresponding charge-neutral bromo precursors. Equilibrium studies conducted with selected [(R-POCOPR′)Ni(NCMe)][OSO2CF3] and (R-POCOPR′)NiBr (R′ = i-Pr) have confirmed facile MeCN/Br exchange between these derivatives and show that the cationic adducts are stabilized with MeO-POCOP, whereas the charge-neutral bromo species are stabilized with MeO2C-POCOP. The potential implications of these findings for the catalytic reactivities of the title cationic complexes have been discussed. (Chemical Equation Presented).
Impact of backbone substituents on POCOP-Ni pincer complexes: A structural, spectroscopic, and electrochemical study
Vabre, Boris,Spasyuk, Denis M.,Zargarian, Davit
, p. 8561 - 8570 (2013/02/23)
When treated at room temperature and in the presence of NEt3 with {(i-PrCN)NiBr2}n, the pincer-type ligands R-POC HOPR′ undergo direct C-H nickellation to give the pincer complexes (R-POCOPR′)NiBr in 45-92% yields (R-POCOP = κP,κC,κP-{R n-2,6-(R′2PO)2C6H 3-n}; Rn = 4-OMe, 4-Me, 4-CO2Me, 3-OMe, 3-CO2Me, 3,5-t-Bu2; R′ = i-Pr, t-Bu). These complexes have been characterized by multinuclear NMR and UV-vis spectroscopy as well as single-crystal X-ray diffraction studies to delineate the impact of R and R′ on Ni-ligand interactions. The solid-state structural data have revealed slightly shorter Ni-Br bonds in the complexes bearing a 4-CO 2Me substituent, shorter Ni-P bonds in the complex bearing t-Bu substituents at the 3- and 5-positions, and longer Ni-P bonds in complexes featuring OP(t-Bu)2 donor moieties. The UV-vis spectra indicate that a 4-CO2Me substituent causes a red-shift in the frequency of the MLCT bands (330-365 nm), whereas the ligand field transitions appearing in the 380-420 nm region are influenced primarily by the P-substituents. Cyclic voltammetry measurements have shown that the oxidation potentials of the title complexes are affected by P- and ring-substituents, oxidation being somewhat easier with t-Bu2PO (vs i-Pr2PO), OMe and Me (vs CO 2Me), and t-Bu (vs Cl). Moreover, oxidation potentials are affected more by the aromatic substituents at the 4-position vs those at the 3- and 5-positions.
