3 ) 3 Si ) 2 N ] 2 P b ▁as ▁the ▁P b ( II ) ▁prec ursor ▁has ▁also ▁been ▁used ▁to ▁synth es ize ▁di ary l pl um by len es , ▁dis ily l pl um by len es , ▁and ▁s atur ated ▁N - h eter oc yc lic ▁pl um by len es . ▁ ▁Alternatively , ▁pl um by len es ▁may ▁be ▁synth es ized ▁from ▁the ▁re duct ive ▁de hal ogen ation ▁of ▁t etra val ent ▁org ano le ad ▁comp ounds ▁( R 2 P b X 2 ). ▁ ▁Str ucture ▁and ▁bond ing ▁▁ ▁The ▁key ▁aspects ▁of ▁bond ing ▁and ▁react ivity ▁in ▁pl um by len es ▁are ▁dict ated ▁by ▁the ▁in ert ▁pair ▁effect , ▁where by ▁the ▁combination ▁of ▁a ▁w iden ing ▁s – p ▁orb ital ▁energy ▁gap ▁as ▁a ▁tr end ▁down ▁the ▁group ▁ 1 4 ▁elements ▁and ▁a ▁strong ▁relativ istic ▁contra ction ▁of ▁the ▁ 6 s ▁orb ital ▁lead ▁to ▁a ▁limited ▁degree ▁of ▁sp ▁hy brid ization ▁and ▁the ▁ 6 s ▁orb ital ▁being ▁deep ▁in ▁energy ▁and ▁in ert . ▁Con sequently , ▁pl um by len es ▁exclus ively ▁have ▁a ▁sing let ▁spin ▁state ▁due ▁to ▁the ▁large ▁sing let – tri ple t ▁energy ▁gap , ▁and ▁tend ▁to ▁exist ▁in ▁an ▁equilibrium ▁between ▁mon omer ic ▁and ▁dim er ic ▁forms ▁in ▁solution . ▁This ▁is ▁in