19872-93-6Relevant articles and documents
Electronic: Versus steric effects of pyridinophane ligands on Pd(III) complexes
Tang, Fengzhi,Park, Sungho V.,Rath, Nigam P.,Mirica, Liviu M.
, p. 1151 - 1158 (2018)
Several new PdII and PdIII complexes supported by electronically and sterically tuned tetradentate pyridinophane ligands MeN4OMe, MeN4, and tBuN4 were isolated and fully characterized (MeN4OMe: N,N′-dimethyl-2,11-diaza[3,3](2,6)-para-methoxypyridinophane; MeN4: N,N′-dimethyl-2,11-diaza[3,3](2,6)pyridinophane; tBuN4: N,N′-di-tert-butyl-2,11-diaza[3,3](2,6)pyridinophane). Cyclic voltammetry studies, UV-vis and EPR spectroscopy, and X-ray crystallography were employed to reveal that the steric properties of the N-substituents of the RN4 ligands have a pronounced effect on the electronic properties of the corresponding PdIII complexes, while the electronic tuning of the ligand pyridyl groups has a surprisingly minimal effect. An explanation for these observations was provided by DFT and TD-DFT calculations which suggest that the electronic properties of the PdIII complexes are mainly dictated by their frontier molecular orbitals that have major atomic contributions from the Pd center (mainly the Pd dz2 atomic orbital) and the axial N atom donors.
Sulfur transfer reactions of a zinc tetrasulfanido complex
Ballesteros Ii, Moises,Tsui, Emily Y.
, p. 16305 - 16311 (2020)
A zinc tetrasulfanido complex supported by a bis(carboxamide)pyridine ligand framework has been synthesized by the insertion of elemental sulfur into the zinc-S(thiolate) bond of a zinc dithiolate complex ([LZn]2-). This paper reports on sulfur transfer reactions of this polysulfanido complex ([1]2-) and compares this behavior to known reactions of metal polysulfido complexes. Complex [1]2- was demonstrated to be in exchange with [LZn]2- and free elemental sulfur in solution. Although triphenylphosphine abstracts sulfur from [1]2- to form [LZn]2-, complex [LZn]2- can abstract sulfur from the zinc polysulfido complex (TMEDA)ZnS6 (TMEDA = N,N,N′,N′-tetramethylethylenediamine). The tetrasulfanido complex [1]2- can also transfer sulfur to dimethyl acetylenedicarboxylate to form a zinc dithiolene complex. These studies demonstrate that the zinc complex with a tetrasulfanido moiety can undergo similar reactions as metal complexes with purely inorganic polysulfido groups, although the final metal-containing products are different.
Synthesis of 2,6-di(1,8-naphthyridin-2-yl)pyridines functionalized at the 4-position: Building blocks for suitable metal complex-based dyes
Nakamura, Shunsuke,Takase, Tsugiko,Oyama, Dai
, p. 1396 - 1405 (2019/05/01)
This study reports the synthesis of a methoxy-substituted 2,6-di(1,8-naphthyridin-2-yl)pyridine using Friedl?nder methodology. The functionalization at the 4-carbon of the methoxy-substituted derivative was confirmed by X-ray structural analysis. Finally, the methyl ether protecting group was cleaved to obtain 2,6-di(1,8-naphthyridin-2-yl)pyridine-4-ol. Using the compounds, coordination behavior to ruthenium(II) center was also examined.
Spectroscopic and DFT Characterization of a Highly Reactive Nonheme FeV-Oxo Intermediate
Fan, Ruixi,Serrano-Plana, Joan,Oloo, Williamson N.,Draksharapu, Apparao,Delgado-Pinar, Estefanía,Company, Anna,Martin-Diaconescu, Vlad,Borrell, Margarida,Lloret-Fillol, Julio,García-Espa?a, Enrique,Guo, Yisong,Bominaar, Emile L.,Que, Lawrence,Costas, Miquel,Münck, Eckard
supporting information, p. 3916 - 3928 (2018/03/26)
The reaction of [(PyNMe3)FeII(CF3SO3)2], 1, with excess peracetic acid at -40 °C generates a highly reactive intermediate, 2b(PAA), that has the fastest rate to date for oxidizing cyclohexane by a nonheme iron species. It exhibits an intense 490 nm chromophore associated with an S = 1/2 EPR signal having g-values at 2.07, 2.01, and 1.94. This species was shown to be in a fast equilibrium with a second S = 1/2 species, 2a(PAA), assigned to a low-spin acylperoxoiron(III) center. Unfortunately, contaminants accompanying the 2(PAA) samples prevented determination of the iron oxidation state by M?ssbauer spectroscopy. Use of MeO-PyNMe3 (an electron-enriched version of PyNMe3) and cyclohexyl peroxycarboxylic acid as oxidant affords intermediate 3b(CPCA) with a M?ssbauer isomer shift δ = -0.08 mm/s that indicates an iron(V) oxidation state. Analysis of the M?ssbauer and EPR spectra, combined with DFT studies, demonstrates that the electronic ground state of 3b(CPCA) is best described as a quantum mechanical mixture of [(MeO-PyNMe3)FeV(O)(OC(O)R)]2+ (～75%) with some FeIV(O)(?OC(O)R) and FeIII(OOC(O)R) character. DFT studies of 3b(CPCA) reveal that the unbound oxygen of the carboxylate ligand, O2, is only 2.04 ? away from the oxo group, O1, corresponding to a Wiberg bond order for the O1-O2 bond of 0.35. This unusual geometry facilitates reversible O1-O2 bond formation and cleavage and accounts for the high reactivity of the intermediate when compared to the rates of hydrogen atom transfer and oxygen atom transfer reactions of FeIII(OC(O)R) ferric acyl peroxides and FeIV(O) complexes. The interaction of O2 with O1 leads to a significant downshift of the Fe-O1 Raman frequency (815 cm-1) relative to the 903 cm-1 value predicted for the hypothetical [(MeO-PyNMe3)FeV(O)(NCMe)]3+ complex.
