acylcobalt complexes according to formulation iii wherein r 3 is substituted or un substituted alkyl substituted or un substituted aryl substituted or un substituted alkoxy or substituted or un substituted aryloxy or amino and l is carbonyl ligand 3 the acylcobalt complexes according to formulation iii wherein r 3 is substituted or un substituted alkyl and l is carbonyl ligand since in solutions the acylcobalt complexes of formula iii actually exist in equilibrium with the corresponding alkylcobalt complexes represented by formula iv wherein r 3 is a substituent that has the same meaning as defined above and the position of the equilibrium may be shifted between the two components as shown by the following equation the catalyst in the polymerisation reaction actually includes precursors iv which can be transformed into compound iii the precursor alkylcobalt complexes iv can be easily transformed into the acylcobalt complexes iii in the presence of carbon monoxide or under the conditions of the copolymerization reaction with high pressure of carbon monoxide accordingly the alkyl complexes may also be used as precursors of the acylcobalt catalysts to catalyze the copolymerization of imines and carbon monoxide and the alkyl cobalt complexes independently prepared may be used to catalyze the copolymerization reaction the acylcobalt complexes precursor iv includes compounds represented by formula iv 1 the acylcobalt complexes according to formulation iv wherein r 3 is substituted or un substituted alkyl substituted or un substituted aryl substituted or un substituted alkoxy substituted or un substituted aryloxy or amino and l is carbonyl ligand phosphorus ligand nitrogen ligand or isonitrile ligand 2 the acylcobalt complexes according to formulation iii wherein r 3 is substituted or un substituted alkyl substituted or un substituted aryl substituted or un substituted alkoxy or substituted or un substituted aryloxy or amino and l is carbonyl.