Synthesis, Characterization, and Variable-Temperature¹H NMR Behavior of Organo-Bridged Dicobaloximes

Abstract

Organo-bridged dicobaloximes with four different dioximes Py(L) 2 CoCH 2 -R-CH 2 Co(L) 2 Py (L ) dmgH, dpgH, chgH, and gH) have been synthesized and characterized by 1 H and 13 C NMR and FAB mass spectroscopy. The cis influencing order observed in dicobaloximes is similar to the previously observed order in monocobaloximes. The cyclic voltammetric results show that an irreversible single-step two-electron reduction of Co III to Co I takes place. The Co-C bond in 4a cleaves during crystallization and results in the formation of o-vinylbenzyl cobaloxime. The variable-temperature 1 H NMR study suggests that the Co-C bond rotation is restricted and its magnitude depends on both the nature of the bridging ligand and the dioxime.

μ-Polymethylene bridged dicobaloximes: Structural, photolysis and thermal decomposition properties

“…l-Polymethylene bridged dicobaloximes were prepared according to the methods of literature [21]. The purification procedure of these complexes was modified in this work by crystallization from the CH 2 Cl 2 /CH 3 CH 2 OH (1:2) solution instead of silica gel column separation.…”

“…In contrast to numerous examples of organo-cobalt complexes with a single cobalt-carbon bond [9][10][11], there is not a plenty of work extended to organo-bridged dicobalt complexes, which are bearing two reactive Co-C bonds [12][13][14][15][16][17][18][19][20][21].…”

“…In 1995, the crystal structure and thermolytic properties of vitamin B 12 dimers were reported by Kräutler [17]. Recently, spectral characterization of biphenyl-and xylylene-bridged dicobaloximes with four different dioximes was described by Gupta et al [21]. However, qualified single crystals for this kind of dicobaloximes have not been obtained since they are unstable in solution [21].…”

“…Recently, spectral characterization of biphenyl-and xylylene-bridged dicobaloximes with four different dioximes was described by Gupta et al [21]. However, qualified single crystals for this kind of dicobaloximes have not been obtained since they are unstable in solution [21]. In this paper, we present the crystal structures analysis, photolytic and thermolysis properties of l-polymethylene bridged dicobaloximes py(dmgH) 2 Co(CH 2 )nCo(dmgH) 2 py, where n = 4, 5, 6, and 12 (1)(2)(3)(4), which have varying length of alkyl chain between the two cobalt atoms.…”

Reactivity studies of aryl cobaloximes with molecular oxygen and electrophiles

“…Despite the large number of crystal structures of cobaloximes and their related compounds, very little information is known on the weak interactions in the crystal packing [5,6,9,13,37].…”