Toward a Square-Grid Polymer: Synthesis and Structure of Pedestal-Mounted Tetragonal Star Connectors, C4R4−Co−C5Y5

We report the synthesis of (cyclobutadiene)cyclopentadienylcobalt derivatives, C 4 R 4 −Co−C 5 Y 5, where R is a rigid arm capable of linear coupling through its para position and the tentacle Y carries a functionality with a large affinity for the surface of mercury. The compounds are needed for a proposed synthesis of a square-grid polymer by 2-dimensional cross-linking polymerization, which calls for cross-shaped star connector modules mounted horizontally on a flat pedestal with a large affinity to a liquid interface. The substituents are R = 4-pyridyl, 4-iodophenyl, 4-bromophenyl, 4-(ethoxycarbonyl)phenyl, 4-(1,12-dicarba- closo -dodecaboran-1-yl)phenyl, 4-carboxyphenyl, 4−[(triethylsilyl)ethynyl]phenyl, Y = H; R = phenyl, Y = (trifluoroacetoxy)mercurio, iodo; R = 4-bromophenyl, Y = (trifluoroacetoxy)mercurio; R = 4-(ethoxycarbonyl)phenyl, Y = [(2-hydroxyethyl)thio]mercurio. Single-crystal X-ray diffraction structures are reported for R = 4-pyridyl, 4-(1,12-dicarba- closo -dodecaboran-1-yl)−phenyl, 4-(ethoxycarbonyl)phenyl with Y = H, R = phenyl with Y = (trifluoroacetoxy)mercurio, and bis[4-(1,12-dicarba- closo -dodecaboran-1-yl)phenyl]acetylene and phenyl[4−(1,12-dicarba- closo -dodecaboran-1-yl)phenyl]acetylene.