SYNTHESES AND CRYSTAL-STRUCTURES OF -HEXABENZO-3,7,11,15,19,23-HEXADEHYDRO[24]ANNULENE (HBC), 3,14-TETRABENZO-3,7,11,15-TETRADEHYDRO[16]ANNULENE (QBC) AND A TETRACOBALT COMPLEX OF QBC - THE 1ST EXAMPLE OF A TRANSITION-METAL COMPLEX OF QBC

,14-Tetrabenzo-3,7,11,15-tetradehydro[16]annulene, or tetrabenzocyclyn e (QBC) and 1,2:5,6:9,10:13,14:17,18: -hexabenzo-3,7,11,15,19,23-hexad ehydro[24]annulene (HBC) have been structurally characterized by X-ray .crystallography. QBC crystallizes in two different space groups; P2(1 )/c with a = 10.652(3) angstrom, b = 10.624(2) angstrom, c = 19.549(4) angstrom, beta = 93.83(2)degrees, V = 2207.4(8) angstrom3, and Z = 4 and P4(1)2(1)2 with a = 9.31) angstrom, c = 25.497(8) angstrom, V = 22 19.6(12) angstrom3, and Z = 4. HBC crystallizes in monoclinic P2(1)/n with a = 14.763(3) angstrom, b = 10.296(2) angstrom, c =22.057(4) angs trom, beta = 108.61(3)degrees, V = 3177.4(11) angstrom3, T = 133 K, an d Z = 4. Reaction of QBC with dicobaltoctacarbonyl has produced a tetr acobalt complex which has been characterized by X-ray crystallography. This complex crystallizes in monoclinic P2(1)/c with a = 14.699(3) an gstrom, b = 17.188(3) angstrom, c = 17.254(3) angstrom, beta = 112.63( 3)degrees, V = 4023.5(13) angstrom3, and Z = 4. Only two of the four C -C triple bonds of QBC bind to dicobalthexacarbonyl moieties even when excess dicobaltoctacarbonyl is used.