Reactions of manganese atoms with cyclic dienes and cycloheptatriene: crystal structure of carbonylbis(1–4-η-cyclohexa-1,3-diene)manganese

Abstract

Condensation of manganese atoms with cyclopentadiene, cyclohexa-1,3-diene, cycloheptatriene, and cyclo-octa-1,3-diene at –196 °C, followed by warming to 20 °C in the presence of CO, has given organomanganese carbonyl complexes in yields of 5–10% based on Mn. The new compounds [Mn(η⁴-C₆H₈)₂(CO)], [Mn(η⁴-C₇H₈)₂(CO)], and [Mn(η³-C₈H₁₃)(CO)₄] have been isolated. A single-crystal X-ray diffraction study of [Mn(η⁴-C₆H₈)₂(CO)] shows that the manganese atom adopts a square-pyramidal configuration with the carbonyl ligand in the axial position. The two hexadiene rings are each folded equatorially away from the Mn atom and the molecule has C_2v symmetry. As in other diene complexes, the two inner C atoms are slightly closer to the metal [Mn–C (mean) 2.078(8)Å] than are the outer C atoms [Mn–C (mean) 2.159(7)Å]. The crystals are orthorhombic, space group P2₁2₁2₁(no. 19) with Z= 4 in a unit cell with a= 8.570(1), b= 17.220(1), and c= 7.562(1)Å. The structure has been refined to R 0.045.