Structural studies of organonitrogen compounds of the transition elements. III. The crystal and molecular structure of μ-methazo-bis(tricarbonyliron)^1,2

The crystal and molecular structure of μ-methazo-bis( tricarbonyl iron), [CH₃NFe(CO)₃]₂, has been determined by a singlecrystal X-ray analysis. This compound crystallizes in space group C_2h2-P2₁/m of the monoclinic crystal system with two dimeric molecules in a unit cell of dimensions a = 7.326 (8) Å, b = 13.090 (14) Å, c = 6.913 (8) Å, and β = 96° 44′ (1′). Observed and calculated densities are 1.66 (2) and 1.70 g/cm³, respectively. Full-matrix anisotropic least-squares refinement of 659 independent counter data yielded a final conventional R factor of 2.8%. The dimeric [CH₃NFe(CO)₃]₂ molecule contains two Fe(CO)₃ groups related by a crystallographic mirror plane and doubly bridged through the nitrogen atoms of the H₃C-N-N-CH₃ ligand. The over-all molecular symmetry is approximately C_2v-2mm. The two bridging nitrogen atoms are bonded to each other at a distance of 1.366 (8) Å, resulting in an acute N-Fe-N angle of 42.7 (2)°. Other molecular parameters which differ significantly from those of related nitrogen-bridged iron carbonyl derivatives include the Fe-Fe and mean Fe-N distances of 2.496 (3) and 1.878 (3) Å, respectively.