ization ▁in ▁general ▁ar ises ▁from ▁the ▁Lewis ▁am ph oter ic ▁nature ▁of ▁pl um by len es , ▁which ▁possess ▁a ▁Lewis ▁acid ic ▁vac ant ▁ 6 p ▁orb ital ▁and ▁a ▁weak ly ▁Lewis ▁basic ▁ 6 s ▁l one ▁pair , ▁which ▁can ▁act ▁as ▁electron ▁accept or ▁and ▁don or ▁orbit als ▁respectively . ▁These ▁di pl um ben es ▁possess ▁a ▁trans - b ent ▁structure ▁similar ▁to ▁that ▁in ▁l ighter , ▁non - car bon ▁con gen ers ▁( dis ilen es , ▁dig erm y len es , ▁dist anny len es ). ▁The ▁observed ▁P b – P b ▁bond ▁lengths ▁in ▁di pl um ben es ▁( 2 . 9 0   –   3 . 5 3   Å ) ▁have ▁been ▁found ▁to ▁typically ▁be ▁longer ▁than ▁those ▁in ▁t etra val ent ▁di pl um ban es ▁R 3 P b P b R 3 ▁( 2 . 8 4   –   2 . 9 7   Å ). ▁This , ▁together ▁with ▁the ▁low ▁computed ▁dim er ization ▁energy ▁( energy ▁released ▁from ▁the ▁formation ▁of ▁dim ers ▁from ▁mon om ers ) ▁of ▁ 2 4   k J   m ol − 1 ▁for ▁P b 2 H 4 , ▁indicates ▁weak ▁multiple ▁bond ing . ▁This ▁counter int uit ive ▁result ▁is ▁due ▁to ▁the ▁pair ▁of ▁ 6 s - 6 p ▁don or - ac ceptor ▁interactions ▁representing ▁the ▁P b