1394791-97-9Relevant academic research and scientific papers
Metathesis reactivity of bis(phosphinite) pincer ligated nickel chloride, isothiocyanate and azide complexes
Li, Huizhen,Meng, Wenjuan,Adhikary, Anubendu,Li, Shujun,Ma, Nana,Zhao, Qianyi,Yang, Qiuyu,Eberhardt, Nathan A.,Leahy, Kendra M.,Krause, Jeanette A.,Zhang, Jie,Chen, Xuenian,Guan, Hairong
, p. 132 - 141 (2016)
A series of nickel pincer complexes of the type [4-Z-2,6-(R2PO)2C6H2]NiX (R = tBu, iPr, Ph; Z = H, CO2Me; X = NCS, N3) have been synthesized from the reactions of the corresponding nickel chloride complexes [4-Z-2,6-(R2PO)2C6H2]NiCl and potassium thiocyanate or sodium azide. X-ray structure determinations of these complexes have shown that the thiocyanate ion binds to the nickel center through the nitrogen. A comparable Ni-N bond length (approx. 1.87 ? for the isothiocyanate complexes and 1.91 ? for the azide complexes) and an almost identical Ni-Cipso bond length (approx. 1.89 ?) have been observed for these complexes. Metathesis reactivity of [4-Z-2,6-(R2PO)2C6H2]NiCl and ligand exchange reactions between the nickel isothiocyanate and nickel azide complexes have been investigated. The metathesis reactions with thiocyanate/azide complexes are faster with a less electron rich and more sterically accessible nickel center. The thermodynamic stability of these nickel complexes has been rationalized using hard-soft acid-base theory (HSAB theory); a harder ligand prefers a less electron rich nickel center. These experimental results have been supported by quantum chemical analysis of the coordinating nitrogen atoms in SCN- and N3.
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 (2015/08/06)
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.
