THE CRYSTAL AND MOLECULAR-STRUCTURES OF A TETRAAZAANNULENE AND ITS COBALT(II) COMPLEX AND THE PREPARATION OF THE CHROMIUM(II) COMPLEX

The structures of the diphenyl-substituted tetraazaannulene dptaaH-2 ( 1) and its cobalt(II) complex Co(dptaa) (2) have been determined by X- ray diffraction. The cobalt(II) complex is low spin (mu(eff) = 2.5 B.M . at 291 K) and except for the two phenyl groups, which are rotated by 30.0-degrees and 38.1-degrees with respect to the CoN4 plane, the mol ecule shows less deviation from planarity than the ligand. The chromiu m(II) complex is low spin (mu(eff) = 2.85 at 292 K and 2.72 B.M. at 87 K) and could not be obtained as a crystalline form. It is believed to be structurally analogous to Co(dptaa) and not to the related chromiu m(II) complex Cr2(tmtaa)4 of the tetramethyldibenzotetraaza[14]annulen e tmtaaH-2, which is essentially diamagnetic and contains an unsupport ed quadruple bond.