Toward a hexagonal grid polymer: Synthesis, coupling, and chemically reversible surface-pinning of the star connectors, 1,3,5-C6H3(CB10H10CX)(3)

A synthetic approach to a two-dimensional grid polymer is proposed and the execution of initial steps is described. Pd-catalyzed coupling of (1,12-dicarba-closo-dodecaboran-1-yl)copper (10) with iodobenzene, m-diiodobenzene, and 1,3,5-triiodobenzene yielded the known 1,12-dicarba-closo-dodecaboran-1-ylbenzene (3) and the new m-bis(1,12-dicarba-closo-dodecaboran-1-y (4) and 1,3,5-tris(1,12-dicarba-closo-dodecaboran-1-yl)benzene (1), yl)benzene (1), respectively. Each arm of the trigonal connector 1 was provided with one or two sticky tentacles by conversion to 1,3,5-tris[12-((3-(ethylthio)propyl)dimetylsilyl)-1,12-dicarba-closo-dodecarboran-1-yl]benzene (7) and 1,3,5-tris[12-(bis(3-(ethylthio)propyl)methylsilyl)-1,12-dicarba-closo-dodecarboran-1-yl]benzene (8). Linear coupling of carboranyl CH terminals through a mercury atom produced very stable dimeric structures from 3 and 4. The carborane 3, its mercury-linked dimer 13, the 1:1 complex of 13 with 2,2'-bipyridyl, and the 2:1 complex of 13 with 2,2'-bipyrimidyl have been structurally characterized by single-crystal X-ray crystallography, but crystals of 1 showed an intriguing disorder and could not be used for molecular structure determination. Grazing incidence IR spectra show that the tentacled species 7 and 8 adsorb firmly on the surface of gold, apparently without a strong preference for a particular orientation. At room temperature, the tritentacled species 7 can be removed readily and the hexatentacled species 8 more slowly by treatment with a THF solution containing fluoride, which severs the tentacles.