ides ▁( OP R 3 ) ▁and ▁sil ox ides ▁([ OS i R 3 ] − ), ▁but ▁far ▁more ▁basic . ▁By ▁varying ▁the ▁R ▁groups ▁on ▁P , ▁a ▁variety ▁of ▁lig ands ▁with ▁different ▁electronic ▁and ▁ster ic ▁properties ▁can ▁be ▁produced , ▁and ▁due ▁to ▁the ▁high ▁ox id ation ▁state ▁of ▁ph osph orus , ▁these ▁lig ands ▁have ▁good ▁thermal ▁stability . ▁Many ▁transition ▁metal ▁ph osph in im ide ▁complex es ▁ ▁have ▁been ▁well - develop ed ▁as ▁have ▁main ▁group ▁ph osph in im ide ▁complex es . ▁▁▁ ▁In ▁main ▁group ▁ph osph in im ide ▁complex es , ▁only ▁terminal ▁and ▁ μ 2 - N - brid ging ▁bond ing ▁modes ▁are ▁observed . ▁▁ ▁The ▁termin ally ▁bound ▁bent ▁lig ands ▁are ▁primarily ▁commonly ▁have ▁M - N - P ▁bond ▁angles ▁r anging ▁from ▁ 1 2 0 - 1 5 0 ° . ▁Both ▁the ▁M - N ▁and ▁N - P ▁bond ▁lengths ▁are ▁appropriate ▁for ▁double ▁b onds . ▁ ▁This ▁bond ing ▁can ▁best ▁be ▁described ▁by ▁a ▁c oval ent ▁single ▁bond ▁with ▁an ▁overlay ing ▁share ▁of ▁polar ▁bond ing . ▁ ▁The ▁ μ 2 - N - brid ging ▁mode ▁ar ises ▁when ▁the ▁free ▁electron ▁pair ▁at ▁nit ro gen ▁gives ▁rise ▁to ▁dim er ization . ▁ ▁These ▁dim er ic ▁complex es ▁yield ▁different ▁M - N ▁bond ▁lengths ▁depending ▁on ▁the ▁lig ands ▁present ▁in ▁the