Structure, conformation and reactivity of organotransition metal π-complexes. part 2¹. X-ray crystallographic characterization of two neutral half-sandwich cr(co)₃ complexes

The preferred solid state conformations adopted by two (É⁶-ligand)Cr(CO)₃ (É⁶-ligand: mesitylene, I; N-phenyl-2, 5-dimethylpyrrole, 2) complexes have been determined via single crystal X-ray crystallographic methods. I adopts a conformation such that the C₆ ring carbon atoms are eclipsed with respect to the carbonyl ligands. Such a conformation is predictable from both steric and electronic considerations. 2, however, adopts a staggered conformation that must be attributed to the steric requirements of the bulky 2, 5-dimethylpyrrole substituent.