 2 is also able to form coordination complexes with transition metal ions . Over 30 such complexes have been synthesized and characterized . 
 2 <a href='drop_aux' title='1'><mark>is</mark></a>also able to form coordination complexes with transition metal ions . Over 30 such complexes <a href='been_done' title='2'><mark>have</mark></a> been synthesized and characterized . 
2 also able to form coordination complexes with transition metal ions . ova 30 such complexes done been synthesized and characterized .