1,12-dicarba-closo-dodecaboranes

Precise placement of metal complexing sites within the infrastructure of a cascade molecule is of importance from a variety of perspectives. In the construction of the above noted Micellane family (cf. Sect. 3.1), we reported the construction of dendrimers with four alkyne moieties at sites equidistant from each other in the interior (17, Fig. 8) [60]. These were treated with decaborane (B10H14) to afford 1,2-dicarba-closo-dodecaboranes (o-carboranes) [71]. Rendering boron clusters soluble in water is of interest because of their use in cancer treatment by Boron Neutron Cancer Therapy. First and second generation water-soluble dendrimers containing four and twelve precisely located boron cluster sites, respectively, were synthesized (e.g., 18). These water soluble dendrimers and their precursors were characterized by 13C-, and nB-NMR spectroscopy (Fig. 8). 

Dicarba-closo-dodecaborane(12) B-Aryl- XIII/3c, 190 l-tert.-Butylperoxycarbonyl- E13/1,... 

Telluran [1,2-Dicarba-closo-dodecaboran( 12)-l -yl]-trichlor-E12b, 306 (O-Carboran + TeCl4)... 

R 299 A. Sterzik, I. Maulana, S. Blaurock, P. Loennecke, E. Rys, V.N. Kalinin and E. Hey-Hawkins, Synthesis of Rac- and Meso-l,2-bis(tert-butyl-chlorophosphino)-1,2-dicarba-closo-dodecaborane( 12) and Transition-Metal Complexes Thereof, p. 85... 

C4H15B1oClHg, 1-Methylmercury-2-chloromethyl-o-carborane, 44B, 573 C4H16AIB9, 3-Ethyl-3-alumina-1,2-dicarba-closo-dodecaborane(12),... 

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. 

Figure 53 The 1,2-, 1,7-, and 1,12-dicarba-closo-dodecaboranes, better known by the more popular names o- (85), m- (86), and / -carborane (87), respectively. (Adapted from ref. 119.)...

INSECT CONTROL TECHNOLOGY] (Vol 14) l,7-Dicarba-closo-dodecaborane(10)... 

N-( 1-12-Dicarba-closo-dodecaboran-l-yl)formamide + triphosgene in CH2CI2 and Et3N... 

The reaction of elemental tellurium with cesium 3-cow io-3-cobaltabis[decahydro-l,2-dicarba-c/o.vo-dodecaborate] in acetic anhydride/sulfuric acid and the methylation of the resulting product with dimethyl sulfate produced 8,8 -methylielluro-3-commo-3-cobaltabis[l,2-dicarba-closo-dodecaborane in low yield3. 

Variable-temperature H n.m.r. studies on 1,2- and l,7-bis(NN-dimethylcarbamoyl)-l,2- and l,7-dicarba-closo-dodecaborane(12) reveal that rotational isomers are present, and they enable estimates to be made of the enthalpies and entropies of. activation for NMe2 rotation.82... 

This complex was prepared from 1,12-dicarba-closo-dodecaborane, 15. The coupling of the C-copper derivative of 15 with 4-methoxyiodobenzene gave the mono-C-arylated compound 16, which was then converted to the C-methoxy-carbonyl derivative 17 by reaction of the lithiate of 16 with methyl chloroformate. 

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