Structural Studies of Organonitrogen Compounds of the Transition Elements. IV. The Crystal and Molecular Structure of Benzo [c] cinnolinebis(tricarbonyliron), C12H8N2Fe2(CO)(6)

A crystallographic determination of the structure of benzo[c]cinnolinebis(tricarbonyliron) has been carried out. Crystals of this material are triclinic, with two formula units in a primitive cell of dimensions a = 7.892 (12) angstrom, b = 9.037 (14) A, c = 14.884 (24) angstrom, alpha = 86 degrees 32' (2'), beta = 113 degrees 39' (2'), and gamma = 107 degrees 0' (2'). The probable space group is CO-PI; observed and calculated densities are 1.64 (2) and 1.645 g/cm(2), respectively. A full-matrix least-squares refinement based upon 1970 independent counter data converged to a conventional R factor of 6.0%. The monomeric, binuclear C12H8N2Fe2(CO)6 molecule contains two Fe(C0)8 groups linked by two Fe-N-Fe bridges through the nitrogen atoms of the benzo[c]cinnoline molecule and also by an iron-iron bond of length 2.508 (4) A. The benzo[c]cinnoline ligand is significantly nonplanar, and the overall molecular symmetry is approximately Ca-m. The N-N bond length is 1.399 (8) angstrom and the mean Fe-N distance is 1.914 (3) angstrom.