Boron chemistry

We can consider the hydroboration step as though it involved borane (BH3) It sim phfies our mechanistic analysis and is at variance with reality only m matters of detail Borane is electrophilic it has a vacant 2p orbital and can accept a pair of electrons into that orbital The source of this electron pair is the rr bond of an alkene It is believed as shown m Figure 6 10 for the example of the hydroboration of 1 methylcyclopentene that the first step produces an unstable intermediate called a tt complex In this rr com plex boron and the two carbon atoms of the double bond are joined by a three center two electron bond by which we mean that three atoms share two electrons Three center two electron bonds are frequently encountered m boron chemistry The tt complex is formed by a transfer of electron density from the tt orbital of the alkene to the 2p orbital... 

The general formula for boric acid esters is B(OR)2. The lower molecular weight esters such as methyl, ethyl, and phenyl are most commonly referred to as methyl borate [121 -43-7] ethyl borate [130-46-9J, and phenyl borate [1095-03-0] respectively. Some of the most common boric acid esters used in industrial appHcations are Hsted in Table 1. The nomenclature in the boric acid ester series can be confusing. The lUPAC committee on boron chemistry has suggested using trialkoxy- and triaryloxyboranes (5) for compounds usually referred to as boric acid esters, trialkyl (or aryl) borates, trialkyl (or aryl) orthoborates, alkyl (or aryl) borates, alkyl (or aryl) orthoborates, and in the older Hterature as boron alkoxides and aryloxides. CycHc boric acid esters, which are trimeric derivatives of metaboric acid (HBO2), are known as boroxines (1). 

A. H. Soloway, F. Alam, R. F. Barth, N. Mafune, B. Bapat and D. M. Adams, in S. Hefmdnek (ed.). Boron Chemistry Proc. 6th Intemat. Meeting on Boron Chemistry, World Scientific, Singapore, 1987, pp. 495-509. 

M11 R. N. Grimes, in Advanees in Boron Chemistry" (W. Siebert, ed.),... 

So far, little attention has been paid to these advantageous aspects of boron chemistry and, therefore, only a limited number of macrocycies or cages... 

As is typical of second-row elements, boron has properties that distinguish it from the other elements in Group 13 as well as from the rest of the metalloids. The unique features of boron chemistry can be attributed to... 

The potential described above is not only of a scientific nature, as all these publications impressively prove. Indeed, it has been applied to bench-scale, pilot-scale and production-scale processing. Examples refer to the fields of Grignard reactions [11], polymerizations [21], boron chemistry ]317], and azo pigment generation ]136]. 

The discovery of polyhedral boranes and polyhedral heteroboranes, which contain at least one atom other than in the cage, initiated a new era in boron chemistry.1-4 Most commonly, of the three commercially available isomeric dicarba-closo-dodecaborane carboranes(l,2-, 1,7-, and 1,12-), the 1,2-isomer 1 has been used for functionalization and connection to organic molecules. The highly delocalized three-dimensional cage bonding that characterizes these carboranes provides extensive thermal and kinetic stabilization as well as photochemical stability in the ultraviolet and visible regions. The unusual icosahedral geometry of these species provides precise directional control of all exopolyhedral bonds. 

Rearrangements of this type are general in boron chemistry and applied widely in organic synthesis . The course of the rearrangement and of the methanolysis is clarified in Scheme 47 <2001JOM(620)51>. 

Liebman, J. F., Greenberg, A., and Williams, R. E. (1988). Advances in Boron and the Boranes. VCH Publishers, New York. A collection of advanced topics on all phases of boron chemistry. 

Muetterties, E. F., Ed. (1967). The Chemistry of Boron and Its Compounds. Wiley, New York. A collection of chapters on different topics in boron chemistry. 

See Current Topics in the Chemistry of Boron, G.W. Kabalka (ed), RSC, Cambridge, 1994 Advances in Boron Chemistry, W. Siebert (ed), RSC, Cambridge, 1997 Contemporary Boron Chemistry, M.G. Davidson, A.K. Hughes, T.B. Marder and K. Wade (eds), RSC, Cambridge, 2000 Boron Chemistry at the Beginning of the 21st Century, Y.N. Bubnov (ed), URSS, Moscow, 2003. 

Strong similarities to boron chemistry are also evident in the dimerization reactions... 

Kabalka, GW. Eds. Current Topics in the Chemistry of Boron. Proceedings of the Eighth International Meeting on Boron Chemistry, University ofTennessee, Knoxville, TN, USA, July 11-15, 1993 Special Publication of the Royal Society of Chemistry No. 143, The Royal Society of Chemistry, Cambridge, UK, 1994. 

Davidson, M. G. Hughes, A. K. Marder, T. B. Wade, K. Contemporary Boron Chemistry. Proceedings of the Tenth International Conference on the Chemistry of Boron, University of Durham, Durham, UK, July 11-15, 1999 Special Publication of the Royal Society of Chemistry... 

Bubnov, Y. N. Boron Chemistry at the Beginning of the 21st Century. Proceedings of the Eleventh International Conference on the Chemistry of Boron, A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, Russian Federation, July 28-Aug. 1, 2002 A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, Russian Federation, 2003. 

Brellochs, B. Abstracts of Euroboron I. European Conference on Boron Chemistry, Platja d Aro, Catalunya, Spain, Sept. 20-24, 1997 Teixidor, F., Vinas, C., Eds. Servei de Publications U.A.B., 08193 Bellaterra, Barcelona, Spain, 1997 p 63. 

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