Reaction of PhaP(C≡CBut)=NSiMe3 (1) with KP(H)Ph afforded 3-(iminophosphorano)-l-phosphaallyl potassium, [K{P(Ph)C(But)=C(H)P(Ph)a=NSiMe3}(OEta)3] [3·(OEta)3], which was recrystallized from EtaO to give a solvent-free complex, [K{P(Ph)C(But)=C(H)P(Ph)a=N-SiMe3}]∞ (3). Treatment of MeaP(C≡CPh)=NSiMe3 (2) with LiP(R)Ph (R＝H, SiMeaBut) formed 2-(iminop hosp horano)-1-phosp haallyllithium, [Li{P(Ph)C{=C(R)Ph}P(Me)a=NSiMe3}-(THE)n] (R＝H, n＝1.5, 4; R＝SiMeaBut, n＝2, 5), via a hydrogen or SiMeaBut group 1,3-P→C migration. Reaction of 4 or 5 with SnCla in 2:1 ratio in EtaO yielded P, N-chelatingtin(II) complexes [Sn{P(Ph)C{=C(R)Ph}P(Me)a=NSiMe3}a] (R＝H, 6; R＝SiMeaBut, 7). Complex 6 was also obtained by treatment of C1SnN(SiMe3)2 with 1 equiv of 4. X-ray data are provided for 3, 5, and 6. Complex 3 is polymeric in the solid state without coordinated solvent molecules, whereas both crystalline 5 and 6 are monomeric.