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The preparation and purification of the heterocyclic diradical benzo-1,2:4,5-bis(1,3,2-dithiazolyl) (BBDTA) is described. Crystals of BBDTA, grown by fractional sublimation at 120-180°C/10 -3 Torr, are monoclinic, space group P2 1 /c, with a ) 4.144(2), b ) 9.0344(13), and c ) 10.7424(16) Å, ) 91.11(3)°, and Z ) 2. The crystal structure consists of discrete, unassociated molecules of BBDTA. The molecules form slipped stacks along the x direction, with the mean molecular plane making an angle of 32.4°to the x axis. The interplanar separation between consecutive molecules along the stacking direction is 3.49 Å. The ESR spectrum of BBDTA is solvent dependent, displaying signals attributable to partially associated materials (not exchange coupled) and to free diradical (exchange coupled). Ab initio molecular orbital calculations suggest a small (ca. 0.5 kcal/mol) separation between the triplet and singlet diradical states. Cyclic voltammetry on BBDTA and the related benzo-1,3,2-dithiazolyl BDTA, coupled with gas phase photoelectron studies on BDTA, establish that both compounds are strong electron donors. Magnetic susceptibility measurements show that BBDTA is essentially diamagnetic up to room temperature; variable temperature single-crystal conductivity measurements provide a band gap of 0.22 eV. The transport properties are discussed in the light of extended Hückel band structure calculations, which suggest a highly three-dimensional electronic structure for bulk BBDTA in the solid state.

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Dibromobis(2-mbthylpyridinb)copper(II) (CO) , although not statistically significant, is in accord with the aforementioned acceptor capabilities of the mercury atom. Within each Mn(CO)o group, the average Cax • • • Ceq nonbonding distance is 2.712 Á. This value is slightly longer than the corresponding value of 2.64 Á observed in Mn2(CO)io41 but is in agreement with the greater angular distortion and greater metal-carbon bond lengths present in Hg-[Mn(CO),],.The mean C-0 distance of 1.154 (10) Á agrees well" with the value of 1.156 Á in Mn2(CO)io and also with values observed in other transition metal carbonyls. There is no significant difference between the axial and equatorial C-0 distances in this compound, which is consistent with the known insensitivity of the C-0 bond length to changes in bond order in the range 2-3. The Mn-C-0 angles have an average value of 178°; thus there is no significant distortion from linearity due to intermolecular packing forces and/or electronic effects.The closest intermolecular contacts (Table III) of range 3.1-3.4 Á indicate no abnormal intermolecular forces.69

The title complexes (III) are obtained according to the scheme and characterized by elemental analysis, IR spectra, and X‐ray structure analysis (for both space group P21/c, Z=4).