{HEAD ~ A catalyst} obtained by contacting a compound of {TAIL ~ a transition metal} of the group V of the Periodic Table represented by formula : 
{ HEAD ~ A catalyst } obtained by contacting a compound of { TAIL ~ a transition metal } of the group V of the Periodic Table represented by formula :
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH