Synthesis of Extended Polyphosphacumulenes

Addition of two equivalents of (Me 3 Si) 2 CLiCl to the C ‐[(diphenyl) (diisopropylamino)phosphonio]‐ P ‐(diisopropylamino)phosphaalkene 2 affords the 1σ 4 ,3σ 3 ‐diphosphabuta‐1,2,3‐triene E1 in 55 % yield. Derivative E1 was fully characterized, including a single‐crystal X‐ray diffraction study. Alkylation of E1 with methyl trifluoromethanesulfonate gives rise to the first C ‐phosphonio‐bis(methylene)phosphorane 5 , which was isolated in 84 % yield. Because the second carbon center is also nucleophilic, cumulene E1 reacts as a “pincer” with BF 3 ⋅OEt 2 , leading to the formation of a novel four‐membered PCBC heterocycle 6 with a betaine‐like structure. Addition of three equivalents of P ‐[diphenyl(diisopropylamino)]methylene phosphorane to (diisopropylamino)dichlorophosphane, followed by addition of one equivalent of CCl 4 , and subsequent deprotonation with lithium hexamethyldisilazide gave rise to 1σ 4 ,3σ 3 ,5σ 4 ‐triphosphapenta‐1,2,3,4‐tetraene F1 , which was isolated in 62 % yield.