▁path way ▁for ▁trans met al ation ▁is ▁through ▁a ▁dis soci ative ▁or ▁sol vent ▁assist ed ▁mechanism . ▁ ▁Here , ▁a ▁lig and ▁from ▁the ▁t etra val ent ▁p all ad ium ▁species ▁dis soci ates , ▁and ▁a ▁coordin ating ▁sol vent ▁can ▁add ▁onto ▁the ▁p all ad ium . ▁ ▁When ▁the ▁sol vent ▁det aches , ▁to ▁form ▁a ▁ 1 4 - elect ron ▁tri val ent ▁intermediate , ▁the ▁organ ost ann ane ▁can ▁add ▁to ▁the ▁p all ad ium , ▁under going ▁an ▁open ▁or ▁cy clic ▁type ▁process ▁as ▁above . ▁ ▁Red uct ive ▁elim ination ▁step ▁ ▁In ▁order ▁for ▁R 1 - R 2 ▁to ▁re duct ively ▁eliminate , ▁these ▁groups ▁must ▁occup y ▁mut ually ▁c is ▁coord ination ▁sites . ▁ ▁Any ▁trans - ad duct s ▁must ▁therefore ▁is omer ize ▁to ▁the ▁c is ▁intermediate ▁or ▁the ▁coupling ▁will ▁be ▁fr ustr ated . ▁ ▁A ▁variety ▁of ▁mechan isms ▁exist ▁for ▁re duct ive ▁elim ination ▁and ▁these ▁are ▁usually ▁considered ▁to ▁be ▁concert ed . ▁ ▁First , ▁the ▁ 1 6 - elect ron ▁t etra val ent ▁intermediate ▁from ▁the ▁trans met al ation ▁step ▁can ▁under go ▁un ass isted ▁re duct ive ▁elim ination ▁from ▁a ▁square ▁plan ar ▁complex . ▁ ▁This ▁reaction ▁occurs ▁in ▁two ▁steps : ▁first , ▁the ▁re duct ive ▁elim ination ▁is ▁followed ▁by ▁coord ination ▁of ▁the ▁newly ▁formed