Reaction of N,N'-bridged 1,10-diazacyclooctadeca-5,14-diynes with [ CpCo(cod)]

The reaction of N,N′-bridged 1,10-diazacyclooctadeca-5,14-diynes 1a–d with [ CpCo(cod)] leads to both intra- and inter-molecular (4) CpCo–cyclobutadiene complexes. The yield of intramolecular complex decreases and the yield of intermolecular complex increases with growing length of the alkane bridge. X-Ray investigations on single crystals of 3a, 3d and 4d reveal that the repulsions between the Cp ring and two CH2-groups in β-position to the cyclobutadiene ring increase from 3a to 3d. Such steric repulsions are not found in 4d.