The crystal and molecular structure of 1-bromobenzocymantrene, (η⁵-C₉H₆Br)Mn(CO)₃

The crystal and molecular structure of tricarbonyl [1-4: 9-η-(1-bromo)indenyl]manganese (III) prepared by reaction of bromo(pentacarbonyl)manganese (II) with diazoindene (I) ("diazo method") has been determined by X-ray diffraction methods. III belongs to the monoclinic space group P2₁/c with unit cell constants a 12.953(9), b 7.627(5), c 13.098(9) Å, and β 110.53(5)°. Full-matrix least-squares refinement converged with a conventional R factor of 0.052 based on 1505 observed reflections. The molecule contains an essentially planar indenyl-π-ligand which is coordinated to the manganese atom through its cyclopentadienyl-like moiety. The bromine ligand is attached to the C(1) position of the indenyl system and has only a very slight influence on the characteristics of the indenyl skeleton. The change from cyclopentadienyl (in cymantrene) to indenyl (in III) produces essentially no disturbance in the normal manganese-carbonyl linkage.