Ferroceneboronic acid

Recently Shinkai and co-workers (Dusemund et al., 1995) have reported the electrochemical properties of ferroceneboronic acid (Fig. 54) in the presence 

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A first application using ferroceneboronic acid as mediator [45] was described for the transformation of p-hydroxy toluene to p-hydroxy benzaldehyde which is catalyzed by the enzyme p-cresolmethyl hydroxylase (PCMH) from Pseudomonas putida. This enzyme is a flavocytochrome containing two FAD and two cytochrome c prosthetic groups. To develop a continuous process using ultrafiltration membranes to retain the enzyme and the mediator, water soluble polymer-bound ferrocenes [50] such as compounds 3-7 have been applied as redox catalysts for the application in batch electrolyses (Fig. 12) or in combination with an electrochemical enzyme membrane reactor (Fig. 13) [46, 50] with excellent results. 

Shinkai and co-workers (Ori and Shinkai, 1995) have recently extended their work using ferroceneboronic acid derivatives to the detection of neutral molecules. A chiral ferroceneboronic acid [101] bearing a tertiary amino group... 

Metalated ferrocenes have served as valuable intermediates for the synthesis of a number of other derivatives. Treatment of lithiated ferrocenes with tributyl borate followed by hydrolysis leads to ferroceneboronic acid (XXXIII) as well as the diboronic acid (73). Ferroceneboronic acid, like benzeneboronic acid, is readily cleaved by cupric bromide or cupric chloride to form the corresponding halo derivatives (XXXIV). Ferrocene-l,l -diboronic acid reacts in the same manner, and either one or two carbon-boron bonds can be cleaved. Further reactions of this type have led to a variety of mixed dihaloferrocenes (73, 75). 

Recently, Shinkai and co-workers (85) reported a ferroceneboronic acid receptor (26). This receptor showed selective electrochemical recognition of fluoride ions over other halides, the redox potential for the ferrocene unit being perturbed on the addition of F . There is, however, only one orbital overlap interaction provided by this host and it is likely the selectivity arises solely due to the hardness of the fluoride anion. 

Jee couplings have been measured by Norrild for D-sorbitol before and after complexation with (5, 5)-2-(iV,iV-dimethyl-l-aminoethyl)ferroceneboronic acid. The results obtained provided strong evidence that a 2,3,5-bound sorbitol complex is formed. 

Shinkai and coworkers reported that ferroceneboronic acid 17 (Fig. 3) acts as an electrochemical anion sensor.It exhibits excellent selectivity for fluoride ions in the presence of other halides and anions such as SCN , S04, and H2PO4 . A i ox value of 1000 M in MeOH/H20 was found for fluoride, compared to values of less than 2 M for chloride and bromide. The fluoride ion is a hard base and. therefore, interacts considerably with the hard boron atom. Oxidation results in the ferrocene group becoming more electron withdrawing. The electron density of the boron atom decreases therefore, the strength of the fluoride complex increases. A biden-tate Z7/ s(boronate) Lewis acid was also shown to act as a fluoride sensor. 

Dusemuncl. C. Sandanayake, M.R.A.S. Shinkai. S. Selective fluoride recognition with ferroceneboronic acid. Chem. Commun. 1995. 3. 333. 

Chiral ferroceneboronic acid derivatives have been synthesized by Ori and tested for chiral electrochemical detection of monosaccharides. The best discrimination was observed for L-sorbitol and L-iditol at pH 7.0 in 0.1 mol dm phosphate buffer solution. Moore and Wayner have explored the redox switching of carbohydrate binding with commercial ferrocene boronic acid. From their detailed investigations, they have determined that binding constants of saccharides with the ferrocenium form are about 2 orders of magnitude greater than those for the ferrocene form. The increased stability is ascribed to the lower pKe of the ferrocenium (5.8) than ferrocene (10.8) boronic acid. 

Chiral ferroceneboronic acid derivatives (- or -h)-60 have been synthesized and tested for chiral electrochemical detection of monosaccharides [138], The best discrimination was observed for L-sorbitol and L-iditol at pH 7.0 in 0.1 mol dm phosphate buffer solution. 

The heat of formation of 2,8,9-trioxa-5-aza-l-boratricyclo[3,3,3,0 > ]undecane in the gas phase has been determined (191.5 0.4 kcalmol- ) as has the bond energy of the N B dative bond. A study describing the recrystallization of triarylboranes has appeared as has a report concerning the solvent isotope effect on the rate of methoxyl exchange between methyl borate and methanol. 2-[l-(o-dihydroxyborylphenyl)-2-phenylethyl]-2-imidazoline has been used for the selective determination of tartaric acid in aqueous solution and the absorption and emission properties of a series of phenyl-substituted dimesityl-boranes have been described. Synchronous spin- and stereo-isomerization of the complex cw-Fe(phen) a(NCBPh 3) 2 have been reported, The kinetics and mechanism of the protodeboronation of ferroceneboronic acid in moderately concentrated HaSO have been studied. ... 

An interesting example of trace metal GC-MIP analysis, utilizing derivatization for organic functional group determination, involves the reaction of ferroceneboronic acid with diols. Brooks and Cole showed quantitative derivatization to give products with good GC behavior... 

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