Process for preparing pyridine homologues by means of substituted cyclopentadienyl cobalt complexes

In a process for preparing a pyridine homologue, which comprises reacting an alkyne with a nitrile in the presence of a cobalt-containing complex, the improvement which comprises conducting said reaction in the presence of a complex of an electron attracting group-substituted .eta..sup.5 -cyclopentadienylcobalt comprising a polyene or an acetylene, which is represented by the general formula ##STR61## wherein A is a C.sub.1 -C.sub.4 alkyl group or a phenyl group;

• n is an integer of from 0 to 2, B is an alkoxycarbonyl group in which the alkoxy moiety contains from 1 to 3 carbon atoms or a C.sub.1 -C.sub.4 acyl group, m is an integer of 1 or 2, and Q is --Co.dbd.R.sub.1 where R.sub.1 is a .eta..sup.4 C.sub.4 -C.sub.12 polyene having from 2 to 4 double bonds, which is unsubstituted or substituted by from 1 to 4 substituents selected from the group consisting of a C.sub.1 -C.sub.4 alkyl group and a C.sub.1 -C.sub.4 alkoxycarbonyl group, and which forms a coordinate bond with the cobalt atom at its diene portion, provided R.sub.1 excludes a polyene composed solely of an aromatic ring, ##STR62## where R.sub.2 is an organic residue of a metallo-cyclic cyclopentadiene composed of two molecules of an acetylene which may be unsubstituted or substituted by from 1 to 4 substituents selected from the group consisting of a C.sub.1 -C.sub.4 alkyl group, a C.sub.1 -C.sub.4 alkoxycarbonyl group, a phenyl group and a cyano group, ##STR63## where R.sub.3 is an acetylene which is substituted by one or two substituents selected from the group consisting of a C.sub.1 -C.sub.4 alkyl group, a C.sub.1 -C.sub.4 alkoxycarbonyl group, a phenyl group and a cyano group and which forms a coordinate bond with the cobalt atom at its triple bond portion, and ##STR64## where A, B, n, m and R.sub.2 are as defined as above.