Direct electrochemical synthesis

TYZOR TPT and the tetraethyl titanate, TYZOR ET [3087-36-3], have also been prepared by direct electrochemical synthesis. The reaction involves anode dissolution of titanium in the presence of the appropriate alcohol and a conductive admixture (3). 

Khan, M., Oldham, G. and Tuck, D.G. (1981) The direct electrochemical synthesis of triphenylphosphine adducts of Group IB monohalides. Canadian Journal of Chemistry, 59, 2714-2718. 

This direct electrochemical synthesis has proved efficient in the preparation of several other complexes, among these the tin derivatives of 3-hydroxy-2-phenylflavone (2) and 2-ethoxyphenol (3), respectively. The use of sacrificial electrodes proved very efficient the produced complex precipitates during electrolysis and is easy to isolate135. 

Chromium(lII) bromide can be prepared directly by treating the metal with bromine in a sealed tube at temperatures variously reported1 -2 as being between 750 and 1000°. The direct electrochemical synthesis described below leads to... 

The direct electrochemical synthesis (Scheme 2) of the addncts of organomagnesinm halides with 2,2 -bipyridine (6) and salts of organodihalogenomagnesinm(II) anions (7) was reported by Hayes and coworkers . Adducts of different stoichiometry and 7 were obtained in the electrochemical oxidation of magnesium in ACN solutions containing organic halides RX (8), a.ro-dihalides XR X (9) and 8 with ammonium salts R NX, respectively. All new products showed none of the typical reactions of Grignard reagents. 

The solvolysis of hexaaquachromium(HI) in DMSO proceeds via the series of complexes [Cr(DMS0)n(H20)6 ]3+ (n = 1 to 6).945,946 The anation and solvolysis of several chromium(III) complexes in DMSO have been studied 947,948 in general the reactions proceed by /d mechanisms. A direct electrochemical synthesis of [Cr(DMSO)6][BF4]3 has been reported.949 A comprehensive review of metal ion complexation by DMSO contains an extensive section on chromium(III).950... 

The direct electrochemical synthesis of metal alkoxides by the anodic dissolution of metals into alcohols containing conducting electrolytes was initially demonstrated by Szilard in 1906 for the methoxides of copper and lead.19 More recently the method has received some attention particularly in the patent literature.29-25 The preparation of the ethoxides of silicon, titanium, germanium, zirconium and tantalum by electrolysis of ethanolic solutions of NH Cl has been patented, although the production of the ethoxides was found to cease after several hours.24,25... 

The metatheis of acetates with the alkali alkoxides (method 5) can be used for the preparation of the methoxides and ethoxides of all three elements and is the only reaction leading to Hg(OR)2 [1623]. The trans-esterification of Zn(OMe)2 (method 6), according to [1121], can be carried out only in the presence of LiOR (forming soluble bimetallic complexes). The direct electrochemical synthesis on the anodic oxidation of metals in alcohols has been described for Zn(OEt)2 and a series of cadmium derivatives (Cd(OR)2 — obtained in the presence of such donor ligands as Dipy, Phen, and Dmso [98]) (method 2). 

Direct electrochemical synthesis is an accessible and mostly one-step method for obtaining coordination compounds [10,201,202,206,509,513,551-554]. The processes are described by a simple scheme (3.236) [555] ... 

Direct electrochemical synthesis is carried out according to the next procedure. Sheets of copper, nickel, or zinc are used as sacrificial anodes, and platinum is used as the cathode. Methanol is used as a solvent and LiC104 as a supporting electrolyte. The ligand (0.5 g) is dissolved in methanol (30 mL) by heating and then the obtained solution is cooled to room temperature. The electrolysis is carried out for 1 hr (current 20 mA applied voltage 20-30 V). The formed solid is filtered, washed with hot methanol (3x5 mL), and dried in air. 

A combination of different techniques can frequently improve yields of final compounds or synthetic conditions, for example a reunion of direct electrochemical synthesis and simultaneous ultrasonic treatment of the reaction system [715]. Reunion of microwave and ultrasonic treatment was an aim to construct an original microwave-ultrasound reactor suitable for organic synthesis (pyrolysis and esterification) (Fig. 3.7) [716], The US system is a cup horn type the emission of ultrasound waves occurs at the bottom of the reactor. The US probe is not in direct contact with the reactive mixture. It is placed a distance from the electromagnetic field in order to avoid interactions and short circuits. The propagation of the US waves into the reactor occurs by means of decalin introduced into the double jacket. This liquid was chosen by the authors of Ref. 716 because of its low viscosity that induces good propagation of ultrasonic waves and inertia towards microwaves. 

Th anode Br2, CH3CN ThBr4(CH3CN)4 Direct electrochemical synthesis using a sacrificial Th anode. Only 0.60 g of metal is dissolved during 6 hr of electrolysis (8 V, 50 mA) 370 ... 

Complexes of lapachol with diverse metals like copper (II), iron (II), iron (III), chromium (III), aluminium (IE), yttrium (El), samarium (IE), gadolinium (IE), and dysprosium (IE) have been investigated [141-144]. Direct electrochemical synthesis of some metal derivatives of lapachol have been carried out [145]. Several P-lapachone hydrazo compounds were synthesized and characterized using spectroscopic techniques including X-ray analyses [146]. Selective aromatic reduction in pyranonaphthoquinones has also been reported [147-148]. 

KUM/TUC] Kumar, N., Tuck, G., The direct electrochemical synthesis of some thorium(lV) nitrate complexes. Can. J. Chem., 62, (1984), 1701-1704. Cited on page 314. 

Shreider, Turevskaya, E. P., Kozlova, N. and Turova, N. Y., Direct electrochemical synthesis of metal alkoxides, Inorg. Chim. Acta, 53, L73 (1981). 

Turevskaya EP, Kozlova NT Turova NY, Belokon AL, Berdyev DV, Kessler VG, et al. The alkoxides of zirconium and hafnium direct, electrochemical synthesis and mass-spectral study. Do M(0R)4 , where M = Zr, Hf, Sn, really exist . Russ Chem Bull 1995 44(4) 734-42. 

DIRECT ELECTROCHEMICAL SYNTHESIS OF INORGANIC AND ORGANOMETALUC COMPOUNDS... 

The final point to be emphasized is that because one starts with a metal which is by definition in the zero oxidation state, the experimental technique will necessarily give preferential access to the lower oxidation states if these can be stabilized in the solvent system in question. In particular, for a number of metals in the Main Group section of the Periodic Table, direct electrochemical synthesis is a simple and attractive way of getting to compounds which otherwise may not easily prepared, and hence provides an entrde to the study of their chemistry. 

It has been known for many years that thiols or disulfides can be reduced electrochemically to the corresponding RS anions. This is the first step in the direct electrochemical synthesis of metal thiolates and their derivatives, since these anions, or more probably the radicals produced when the anions discharge at the anode, react with a variety of metals. We have carried out successful syntheses with the elements Co, Ni, Cu, Ag, Au, Zn, Cd, Hg, In, Tl, Sn and Pb to give M(SR)n, with R = Et, t-Bu, n-Bu, C5H11, Ph, 0-, m-, p-tolyl, 2-naphthyl, etc. (not all combinations) [32]-[37]. As with the halide systems, one can equally well produce the compounds themselves, or their derivatives, by appropriate adjustment of the solution phase conditions. The synthesis of these substances is experimentally simple and straightforward. 

One interesting and unexpected aspect of these syntheses is that the products of the electrochemical oxidation of copper included some molecules with unusual cage structure based on CU4S4, CU2S2, CU4P4, etc., rings [35], [41]-[44]. This is not the place to attempt a discussion of such structures, nor those of the [M4(SPh)io] anions (M = Zn, Cd), since good reviews have already been published [45,46], but their easy accessibility by direct electrochemical synthesis is yet another feature of this versatile method. 

It seems likely that the use of liquid ammonia media may offer some advantages in the direct electrochemical synthesis of low oxidation state complexes. We hope to investigate this matter in the future. 

Tuck, D.G. (1979) Direct electrochemical synthesis of inorganic and organometallic compounds . Pure and Appl. Chem., 51, 2005-2018. 

Oldham, C., Taylor, M.J., and Tuck, D.G. (1985) Direct electrochemical synthesis of metal thiocyanate complexes , Inorg. Chem. Acta, 100, L9-10. 

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