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 π-aryl based carbene, 2,2′,4,4′,6,6′,-hexabromodiphenylmethylene 2 in both crystals and fluid solutions. This paper describes ESR detection of 2 in the crystal 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 = 9.993angstrom, b = 13.261angstrom, c = 12.743angstrom, θ = 91.88°, Z = 4, and the space group P21/n. The two phenyl rings of 2,4,6-bromo-substitution make bent perpendicular conformation with 139 degree of the bond angle at the diazo methane. Non-bonded contacts shorter than the van der Waals radii were found between the nitrogen and bromine atoms of the nearest neighboring molecules.