Nucleophilic addition to coordinated cycloheptatriene: A mechanistic and structural study

Article abstract of DOI:10.1021/om00124a013

The addition of phosphorus and nitrogen donor nucleohiles (Nu) to the cycloheptatriene ring in (C₇H₈)Mn(CO)₂L⁺ (1; L = CO, PPh₃) yields (exo-NuC₇H₈)Mn(CO)₂L⁺. N,N-Dimethylaniline undergoes an electrophilic aromatic substitution reaction with 1 (L = CO) to give (exo-Me₂NC₆H₄C₇H ₈)Mn(CO)₃, in which the carbon para to the NMe₂ substituent is bonded to the C₇H₈ ring. Kinetic studies of the addition reactions show that 1 (L = CO) is an extremely reactive electrophile and that the relative nucleophilic reactivities are the same as found for other, less reactive, organometallic substrates as well as for free carbonium ions. A single-crystal X-ray analysis of [(exo-PPh₃C₇H₈)Mn(CO)₃]BF ₄ showed that it crystallizes in the monoclinic space group P2₁/c with a = 9.595 (3) ?, b = 14.580 (4) ?, c = 19.574 (6) ?, β = 107.23 (8)°, and R_w = 0.0448. The structure shows that the dienyl carbons (C4-C5-C6-C7-C8) are planar and form a dihedral angle of 45.8° with the nonbonded plane (C10-C9-C8-C4). The carbon skeleton defining the cycloheptadienyl ring possesses approximate C₈ symmetry.