ELECTRONIC AND MOLECULAR-STRUCTURES OF ROOM-TEMPERATURE STABLE TRIPLET CARBENE AS STUDIED BY ESR AND X-RAY CRYSTAL ANALYSIS OF THE DIAZO PRECURSOR

We report the first room-temperature stable triplet pi-aryl based carb ene, 2,2',4,4',6,6',-hexabromodiphenylmethylene 2 in both crystals and fluid solutions. This paper describes ESR detection of 2 in the cryst al of the diazo precursor 1 and the molecular and crystal structure of the precursor obtained by X-ray diffraction at room temperature. The crystal is monoclinic with cell dimensions, a = 9.993 Angstrom, b = 13 .261 Angstrom, c = 12.743 Angstrom, theta = 91.88 degrees, Z = 4, and the space group P21/n. The two phenyl rings of 2,4,6-bromo-substitutio n make bent perpendicular conformation with 139 degree of the bond ang le at the diazo methane. Non-bonded contacts shorter than the van der Waals radii were found between the nitrogen and bromine atoms of the n earest neighboring molecules.