Abstract
Several derivatives of cyclopentadienylcobalt complexes having a pendant amino‐functionalised side chain (Cp′) are described, the cyclopentadienyl ligands being (2‐aminoethyl)cyclopentadienyl, (2‐piperidinoethyl)cyclopentadienyl,1‐(2‐piperidinoethyl)‐2,3,4,5‐tetraisopropylcyclopentadienyland 2‐picolylcyclopentadienyl. Chelation by the amino‐functionalised side chain occurred when the Cp*‐cobalt(I) dicarbonyl complexes 5, 6, 7 and 8 were oxidised by iodine, thereby forming the corresponding Cp*‐cobalt(III) chelates 9, 10, 11 and 12, respectively, through the diiodocarbonyl intermediates 5′, 6′, 7′ and 8′, respectively. The stabilities of the intermediates differ greatly due to the different amino functions in the pendant side chain. Structural studies of 9, 10 and 12 were carried out and the correlation of the I–Co–I angles and the repulsive forces from the amino‐functionalised groups with the stabilities of the intermediates is discussed. The diiodocarbonyl‐η^5^‐(2‐piperidinylethyl)cyclopentadienylcobalt(III) intermediate 6′ becomes reduced to 6 by the CO released upon chelation of the former when the concentration of CO reaches about 0.088 mol L^−1^. The chelated piperidine group in 10 could be easily replaced by triphenylphosphane to form the diiodotriphenylphosphanyl‐η^5^‐(2‐piperidinioethyl)cyclopentadienylcobalt(III) iodide dichloromethane solvate 13 in the presence of hydrogen iodide. A strong N–H**···I hydrogen bond with an N···I distance of 3.414(14) Å and a D–H···**A angle of 164.1° were found in 13. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)