The Crystal and Molecular Structure of Tris(l, 10-phenanthroline)nickel(II) Pentacarbonylmanganate( ---I), [Ni(l, 10-phen)3][Mn(CO)₅]

The crystal structure of tris(l, 10-phènanthroline)nickel(n) pentacarbonylmanganate( --- I), [Ni(phen)₃] [Mn(CO)₅]₂, has been determined from X-ray counter data collected at ---123 ± 2°. Discrete Ni(phen)₃²⁺ cations and Mn(CO)₅- anions crystallize in space group PI with lattice constants a = 13.918 (5), b = 14.325 (5), c = 12.399 (8) å, a = 102.16 (4), β = 113.22 (4), -y = 98.46 (3)° at ---121°. The observed density of 1.535 (10) g/cm3 at 25° agrees well with that of 1.546 g/cm3 calculated for two formula units in the cell found at ---123°. The Ni(phen)32 + cations show approximate threefold symmetry. The N-Ni-N bite averages 79.4 (5)°; the variations in N-C and C-C bond distances in the ring system are consistent with previous structures. The Mn(CO), 5- anions are trigonal bipyramidal with a small distortion most noticeable in the equatorial plane, where the C-Mn-C bond angles range from 117.5 (3) to 125.0 (4)°. The average of the axial Mn-C bonds is slightly, but not significantly, longer than the average of the equatorial bonds. The Mn-C bond lengths range from 1.77 (1) to 1.82 (1) A; the difference in axial and equatorial bond averages is 0.02 (2) A. This difference is considered together with other d8 complexes having five identical ligands about the central metal atom.