▁s igma ▁bond ▁between ▁R 1 ▁and ▁R 2 ▁to ▁the ▁metal , ▁with ▁ult imate ▁dis soci ation ▁yield ing ▁the ▁couple d ▁product . ▁ ▁The ▁previous ▁process , ▁however , ▁is ▁sometimes ▁slow ▁and ▁can ▁be ▁greatly ▁acceler ated ▁by ▁dis soci ation ▁of ▁a ▁lig and ▁to ▁yield ▁a ▁ 1 4 - elect ron ▁T ▁sh aped ▁intermediate . ▁ ▁This ▁intermediate ▁can ▁then ▁rear range ▁to ▁form ▁a ▁Y - sh aped ▁ad duct , ▁which ▁can ▁under go ▁faster ▁re duct ive ▁elim ination . ▁ ▁Finally , ▁an ▁extra ▁lig and ▁can ▁associate ▁to ▁the ▁p all ad ium ▁to ▁form ▁an ▁ 1 8 - elect ron ▁trig onal ▁b ip y ram idal ▁structure , ▁with ▁R 1 ▁and ▁R 2 ▁c is ▁to ▁each ▁other ▁in ▁equ atorial ▁positions . ▁ ▁The ▁geometry ▁of ▁this ▁intermediate ▁makes ▁it ▁similar ▁to ▁the ▁Y - sh aped ▁above . ▁ ▁The ▁presence ▁of ▁bul ky ▁lig ands ▁can ▁also ▁increase ▁the ▁rate ▁of ▁elim ination . ▁ ▁Lig ands ▁such ▁as ▁ph oph ines ▁with ▁large ▁b ite ▁angles ▁cause ▁ster ic ▁rep ulsion ▁between ▁L ▁and ▁R 1 ▁and ▁R 2 , ▁resulting ▁in ▁the ▁angle ▁between ▁L ▁and ▁the ▁R ▁groups ▁to ▁increase ▁and ▁the ▁angle ▁between ▁R 1 ▁and ▁R 2 ▁to ▁hence ▁decrease , ▁allowing ▁for ▁quick er ▁re duct ive ▁elim ination . ▁ ▁K inet ics ▁ ▁The ▁rate ▁at ▁which ▁organ ost ann anes ▁trans met al