Electrochemical synthesis of halogen derivatives of bis(1,2-dicarbollyl)cobalt(III)

Abstract

A convenient electrochemical method for the synthesis of 8,8´ dihalogen derivatives of bis(1,2 dicarbollyl)cobalt(III) anion [8,8´ X 2 3,3´ Co(1,2 C 2 B 9 H 10 )] -(X = Cl, Br, I) was developed. The method includes the electrolysis of a solution of alkaline metal halide and tetramethylammonium salt of bis(1,2 dicarbollyl)cobalt(III) in methanol at 50 °С in a one compartment electrochemical cell with a nickel cathode and platinum anode.Bis(dicarbollyl)cobalt derivatives 1 found wide use for the liquid extraction of radionuclides. 2,3 . Many both ra dioactive and stable nuclides (Li + , Na + , K + , Rb + , Cs + , Tl + ; Ca 2+ , Ba 2+ , Ra 2+ , Pd 2+ ; lanthanides, etc.) can suc cessfully be separated and isolated using bis(dicarbol lyl)cobalt and its derivatives. 4-7 In addition, bis(dicarbol lyl)cobalt derivatives turned out to be promising compo nents of ion selective electrodes and phase transfer catalysts. 1 The introduction of a halogen into the [3,3´ Co(1,2 C 2 B 9 H 11 ) 2 ] -framework enhances its resistance to strong acids, oxidants, and intense radioactive radiation, 3,8,9 which extends possibilities of practical use of these com pounds. Hence, the halogen derivatives of bis(dicarbol lyl)cobalt can thus be challenging extracting agents for decontamination of radioactive waste. 7,10-14The syntheses of halogen derivatives of bis(1,2 di carbollyl)cobalt by treatment with halogens, 9,15,16 iodine chloride, 17,18 hypochlorous acid, 9 and chloro or bromo succineimide are described in the literature. 9 It was shown that substitution occurs stepwise in these cases: first, hy drogen atoms were displaced from positions 8 and 8´ ad jacent to the metal atom followed by substitutions of fur ther halogens at positions 9, 9´, 12, and 12´ most remote from the carbon atoms. 15 A drawback of all listed methods is a necessity to use expensive halogenating agents and the formation by prod ucts (in particular, highly corrosive gaseous hydrogen halide).In this work, we attempted to prepare Me 4 N[8,8´ X 2 3,3´ Co(1,2 С 2 В 9 Н 10 ) 2 ] (Х = Cl, Br, I) by the coupled electrolysis of Me 4 N[3,3´ Co(1,2 С 2 В 9 Н 10 ) 2 ] (1) and al kaline metal halide in methanol. Results and DiscussionCompound 1 was halogenated with a halogen species produced by the anodic oxidation of a halide ion. The reaction of 1 with halogen affords a halogen derivative of bis(1,2 dicarbollyl)cobalt and halide ion. The electro chemical halogenation of 1 is presented in Scheme 1.The halide ions formed by the chemical reaction un dergo anodic oxidation, which makes possible regenera tion of the halogenating agent to form a target product in a preparative yield.It is known 19 that the separation of mixtures of the mono and dihalogen substituted products and their iso lation in the individual state are labor consuming pro cesses. The dihalogen derivatives are chemically, ther mally, and radiationally more stable than the unsubstituted and monohalogenated bisdicarbollyl complexes of transi tion metals. Therefore, the purpose of our work was to find conditions f...

Correlations in 11B NMR spectra of dihalo derivatives of bis(1,2-dicarbollyl)cobalt(III)

“…(2), we obtain the calculated value δB(6) = -0.71 ppm, while according to the experimental data in [6] it is -3.17 ppm. The difference (∆ δ ) between the calculated and experimental values is 2.46 ppm.…”

“…2) lies on the straight line, while the B(4, 7) signal is shifted upfield. The splitting of the B (4,7,9,12) signal for compound 2 can also be explained from the standpoint of A-and T-effects, which are most pronounced for fluoro derivative 2 compared with the other halo-substituted analogs 3-5.…”

“…Compound 1 was synthesized according to the familiar procedure in [5], by reaction of CoCl 2 with the potassium salt of the 7,8-dicarbaundecaborate anion in aqueous alkaline solution. Compounds 3-5 were obtained by electrolysis of a solution of Me 4 N + [3,3′-Co(1,2-C 2 B 9 H 11 ) 2 ] -in absolute methanol in the presence of the halide of the corresponding metal at 50 o C, according to the procedure in [6,7]. We used platinum as the anode and a nickel electrode as the cathode.…”

“…The 11 B NMR spectra of compounds 3-5 were obtained on a Bruker AMX-400 spectrometer at a working frequency of 128.4 MHz in acetone-d 6 [6,7]. For compounds 1 and 2, we used data on assignment of the signals in the 11 B NMR spectra recorded on an INOVA 400 spectrometer at a working frequency of 128.4 MHz in acetone-d 6 [8].…”

New Fulvalenium Salts of Cobalt Bis(dicarbollide): Crystal Structures and Electrical Conductivities

“…The X-ray structure analysis revealed partial substitution of a hydrogen atom at position 7 of the metallacarborane anion by a chlorine atom. The substitution can be the result of electrochemical reaction of cobaltacarborane with 1,2,2-trichloroethane as a source of chlorine and is not typical for the chemistry of cobalt bis(1,2-dicarbollide) [4,14].…”