2-Substitutedm-Xylylene-Bridged Dicobaloximes:  Structure−Property Relationship Using Variable-Temperature¹H NMR Study

Abstract

Xylylene-bridged dicobaloximes with a substituent at the 2-position having varying electronic and steric properties have been synthesized and characterized by 1 H and 13 C NMR spectroscopy. The variable-temperature 1 H NMR study of these complexes shows that the electronic cis influence is an important phenomenon for the Co-C bond rotation. The coalescence temperature of the dioxime protons correlates well with the ortho substituent constant. The crystal structure of a 2-nitro-m-xylylene-bridged dicobaloxime, Py(dmgHPy, is reported. The X-ray structural data support the 1 H NMR findings. Experimental SectionGeneral Comments. Cobalt chloride hexahydrate, dimethylglyoxime (SD Fine, India), diphenylglyoxime, 2-fluoro- † Dedicated to Prof.

Biphenyl-Bridged Dicobaloximes: Synthesis, NMR, CV, and X-Ray Study

“…In the 1 H NMR spectra, Co−CH 2 , dioxime, O−H···O, and pyridine resonances and in the 13 C NMR CN, Co−CH 2 , and pyridine are clearly distinguished and are easily assigned on the basis of their chemical shifts. The assignments are consistent with the related organo-bridged complexes reported from our group. , …”

“…Organo-bridged dicobaloximes of the type B(L) 2 Co-R-Co(L) 2 B (L = dioxime) were virtually unknown until recently . In our recent studies we saw that the ortho and meta xylylene-bridged dicobaloximes exhibited very interesting NMR behavior in solution; the cobalt-bound CH 2 became diasteretopic and the dioxime protons showed nonequivalence at subzero tempearture . This was attributed to the restricted rotation of the Co−C and/or C−Ph bond.…”

Discrete Binuclear Cobalt(III) Bis-dioximates with Wheel-and-Axle Topology as Building Blocks To Afford Porous Supramolecular Metal–Organic Frameworks

“…Although the chemistry of mononuclear bis-dioximates is rich and well documented, they are still intensively studied, for example as cheap photocatalysts for light-driven hydrogen production. − Surprisingly not much data have been reported on the polymers − and binuclear complexes − based on [M­(dioxH) 2 ] building blocks linked by pyridine based rod-like bridges, though they also revealed photocatalytic properties . Such binuclear complexes possess wheel-and-axle topology and provide useful molecular building blocks for creating flexible metallorganic supramolecular networks and porous architectures in crystal − because they cannot pack efficiently without including solvent molecules.…”

Synthesis of novel ferrocene containing vic-dioxime ligands and their Ni(II), Cu(II) and Co(II) complexes: Spectral, electrochemical and biological activity studies

“…The potential applications of these compounds and their complexes have been shown to be useful in many search areas such as medicine [4], bioorganic systems [5], catalysis [51], and electrooptical sensors [6]. The cobaloximes have acquired an independent research field among the oxime complexes because of their usage as model compounds for the study of the vitamin B 12 coenzyme [7,8]. Like oximes, ferrocene-based ligands have been employed in various fields, such as semiconductors, [9] biosensors, [10] asymmetric catalysis, [11] and nonlinear optics.…”