Boron, functions

In the area of ion sensing, cation recognition by electrodes containing functionalized redox-active polymers has been an area of considerable interest. Fabre and co-workers have reported the development of a boronate-functionalized polypyrrole as a fluoride anion-responsive electroactive polymer film. The electropolymerizable polypyrrole precursor (11) (Fig. 11) was synthesized by the hydroboration reaction of l-(phenylsulfonyl)-3-vinylpyrrole with diisopinocampheylborane followed by treatment with pinacol and the deprotection of the pyrrole ring.33 The same methodology was utilized for the production of several electropolymerizable aromatic compounds (of pyrrole (12) (Fig. 11), thiophene (13 and 14) (Fig. 11), and aniline) bearing boronic acid and boronate substituents as precursors of fluoride- and/or chloride-responsive conjugated polymer.34... 

Hartwig and Hillmyer have recently reported the Rh-catalyzed borylation of polyolefins to yield boronate-functionalized polymers (58) (Fig. 37) in a single step.83 The number-average molecular weight of the borylated polymer that was obtained at a B2pin2 polyethylethylene ratio of 0.3 was found to be the highest (Mn = 52,000 and PDI = 1.09) among the developed boronate-functionalized polyolefins. 

Figure 37 The boronate-functionalized polymer (58) obtained by the Rh-catalyzed borylation of polyolefins. (Adapted from ref. 83.)...

Wolfe and Wagener have developed main-chain boronate polymers (59) (Fig. 38) by the acyclic diene metathesis (ADMET) polymerization of symmetrical ,oj-dienes, containing both methyl- and phenyl-substituted boronate functionalities using Mo and Ru catalysts.84 The ring-opening metathesis polymerization (ROMP) of several norbornene monomers containing methyl- and phenyl-substituted boronates into... 

Boron Mechanism. Boron functions as a flame retardant in both the condensed and vapor phases. Under flaming conditions boron and halogens form the corresponding trihalide. Because boron (rihalides are effective Lewis acids, they promote cross-linking, minimizing decomposition of the polymer into volatile flammable gases. These trihalides arc also volatile thus they vaporize into the (lame and release halogen which Ihen functions as a Maine inhibitor. 

We have prepared Enk with ferrocene and cobaltocenium carboxylic acid attached to its amino end [38]. In a series of papers, we have explored the use of the tris(pyrazolyl)borate (Tp) ligand family [39-41]. Boron-functionalized,... 

Using a different approach, the research gronps of Fabre and Freund have synthesized boronate-functionalized conjugated polymers, which serve as electrochemical sensors. For example, a conjugated redox-active film of polypyrrole (174) was electrodeposited onto a platinum electrode from acetonitrile solution. Addition of fluoride anions led to a new redox system that showed an anodic shift relative to polypyrrole itself, which was attributed to fluoride binding to the boronate group. A related poly(aniline boronic acid) (175) was also reported and studied for saccharide detection. " ... 

Boron-functionalized MC2B4 and MC2B3M Clusters and their Applications... 

Boron-functionalized metallacarboranes might also serve as precursors to more complex organometallic systems such as the trigonally symmetrical 28 (Scheme 7). In a recent development,12 we have found a route to water-soluble B-hydroxy derivatives 30. 

Scheme 10.21). It is quite common to use M to designate a metallic function. In Scheme 10.21, M represents tin and boron functions. The mechanism is analogous to that described previously. 

The second possible improvement that we might seek is to vary the Slater exponent so that a better match to the boron function is obtained. This is a matter best investigated after Chapter 3, when we have considered the role of orthogonality as a fundamental requirement in solution procedures for calculation of orbital energies and orbital functions. But, it is a good exercise, to demonstrate the versatility of the spreadsheet approach. A better result is shown in Figure 1.25. It follows, simply, from setting the Slater exponents for the Slater function and the sto-3g) set equal to 1.00 in cells G 3 and G47. 

Dienes containing the boronate functionality, with x = 9 or 11, undergo ADMET polymerization in the presence of Ru(=CHPh)(Cl)2(PCy3)2 (Wolfe 1996). ... 

The combination of versatile chemistry and similarity to aluminum makes boron an attractive choice for protecting group chemistry. This has been amply demonstrated in a series of papers by Chung et al. from work initially carried out at Exxon. Patents published in 1988 disclose the use of boron-functionalized monomers in both homo- and copolymerizations using heterogeneous TiCla (pretreated with aluminum alkyl) AlEt2Cl formulations. - Monomers were prepared by monohydroboration of dienes (1,4-pentadiene, 1,7-octadiene, etc.) with 9-borabicyclo-[3.3.1]nonane (9-BBN). Near quantitative yields of the homopolymers of 7-octenyl-9-BBN and 5-hexenyl-9-BBN could be obtained (eq 6). 

Both vinyl- and alkynyl-9-BBN derivatives are effective dieno-philes in Diels-Alder cycloadditions, leading to boron-functionalized cyclohexenes in a selective manner (eqs 37 and 38). Silylated allenylboranes add selectively as allylboranes to aldehydes, a reaction which has been effectively used to prepare the steroid nucleus through a Hudrlik elimination followed by a Bergman rearrangement (eq 39). ... 

Nicolas. M. Fabre. B. Simonet, J. Boronate-function- 121. alized polypynole as a new fluoride sensing material. 

The reaction works for both cyclic (34a-c) and acylic (34d,e) alkenes (Table 4.5). In most processes, the product is a vinyl boronate (37a-d). However, the C-H functionalization of cycloheptene gives allyl boronate 38. The mild neutral reaction conditions allow the synthesis of silyl and boronate functionalized species 37c,d as well. 

The special binding ability of the organo-boron functionalized 1,2-dithienylcyclo-pentene DTE-BMes2 with fluoride (tetrammonium fluoride (TBAF)) and mercuric ions (Hg(C104)2) allows the modulation of its spectral properties, in its open and PSS states [46]. 

Based on the hypothesis that the generation of a boron enolate intermediate would be possible through the cooperative intramolecular interaction between a basic and a boronate function, Whiting and co-workers (239) prepared a series of bifunctional aminoboronate systems and examined the catalytic activities in a direct aldol reaction of aldehydes and hydroxyacetone. Of the several analogues for the aminoboronate catalyst examined, an ate complex 169, the... 

Although the first report on boronic acids was published in 1862, boronate affinity materials have not been extensively investigated until recently. In recent years, various boronate-functionalized materials, " such as macroporous monoliths, " " nanoparticles, and mesoporous materials, have been developed into important tools for the facile selective extraction of cis-diol-containing compounds. With these matrices, several important materials with teamed boronate affinity and boronate avidity as well as boronate affinity-based molecularly imprinted polymers have been prepared. 

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