Cobalt metallacycles. Part 14. Facile transformation of η4-diene complexes to metallacyclopentenes. Preparation and molecular structures of [Co(η5-C5H5){η4-PhNCC(Ph)C(Ph)CNPh}] and [Co{C(NR)C(Ph)C(Ph)C(NR)}(η5-C5H5)(CNC6H3Me2-2,6)](R = C6H3Me2-2,6)

Abstract

The reaction of [Co(η⁵-C₅H₅)(PPh₃)(R¹CCR²)](1)(R¹= Ph, R²= Ph or CO₂Me) with excess aryl- or t-butyl-isocyanide, R³NC, gives the di-iminobutadiene complexes [Co(η⁵-C₅H₅)(η⁴R³NCC(R¹)C(R²)CNR³)](2). Complexes (2) react with the ligands L (L = PhNC, 4-MeC₆H₄NC, 2,6-Me₂C₆H₃NC, CO, or PMe₃) to give the 2,5-di-iminocobaltacyclopentene complexes [C[graphic omitted](NR³)}(η⁵-C₅H₅)L](3). The structures of (2a)(R¹= R²= R³= Ph) and (3f)(R¹= R²= Ph, R³= 2,6-Me₂C₆H₃, and L = 2,6-Me₂C₆H₃NC) have been determined from X-ray data. Complex (2a) crystallizes in the monoclinic space group Cc, with unit-cell dimensions a= 19.756(4), b= 10.904(3), c= 12.986(3)Å, β= 114.44(3)°, Z= 4, and R= 0.055 for 2 609 independent reflections. Crystals of (3f) are monoclinic, space group P2₁/n, with a= 16.362(4), b= 19.119(3), c= 11.952(3)Å, β= 90.73(2)°, Z= 4, and R= 0.047 for 2 873 independent reflections.