These distances indicate considerable mesomeric interaction of the free electron pair on C52 with the )C=O groups, with the free electron pair on the imide nitrogen, and with the phosphorus atoms.The cyclopentadiene ring in (5) is pentahapto bonded to molybdenum. The bond lengths in the M O ( C O )~( C~H~) part of the molecule are normal (in pm): (1) A further proof for the constitution of (5) is its smooth oxidation to (4) [eq. (b)]:(5) + Iz + (4) + HI Procedure (b)A solution of [MO(C,H,)(CO>,]~ (1.2 g, 2.45 mmol) and (PP) (2.36 g, 4.91 mmol) in boiling toluene is stirred until evolution of CO is complete. Brown (3) crystallizes from the dark-brown solution; yield 95%.-The iodide (4) is prepared by oxidation of (3) (2.38 g, 3.41 mmol) with iodine (0.435 g, 3.42 mmol) in ether/l,2-dichloroethane (1 : 1) at "C; dark-red crystals, yield 80%.-When (3) is heated for several days at 80°C in toluene, (5) is obtained as large, yellow crystals; yield 40-60%.

The thermal rearrangement of the N‐alkyl‐ated amino(imino)phosphorane (1) into the three‐membered ring (2) is a surprising reaction, for N‐silylated analogues of (1) form diiminophosphoranes by 1,3‐shift of a silyl group. (R = iPr, R′ = tBu)

Reaktion des vollstandig silylierten Iminophosphans 1 mit a-alkylierten Diazoethanen bzw.-methanen ergibt die Iminomethylenphosphorane 6 -9, 12, 13. Investigations in the System Iminophosphane/Diazoalkane: Iminomethylenephosphoranes and their Addition Products')The reaction of the fully silylated iminophosphane 1 with a-alkylated diazoethanes or -methanes gives iminomethylenephosphoranes 6 -9, 12, 13. The ethylidenephosphorane 12 forms the cyclic diazadiphosphetidine 15 with accompanying migration of silyl groups, while in the presence of iminophosphane 1 an azadiphosphetidine 16 is obtained. The corresponding conversion of 1 with diazomethane leads, on the other hand, directly to the diphosphetane 19. -In contrast to 1, the imine-alkylated iminophcsphane 20 reacts with 2-diazopropane with accompanying silyl group displacement to the iminomethylenephosphorane 21. -The influence of steric effects shows itself in the behaviour of these compounds in reactions with further diazoalkanes. Thus, the reaction of 18 with diazomethane, leads exclusively to the phosphirane 22, and of 6 mostly to the phosphirane 23, while using alkylated diazoalkanes instead yields 1 : 1-adducts from iminomethylenephosphorane and diazoalkane (26,27). -The spectroscopie data show that the influence of substituents can be understood as consequence of the polarisation effect of the ylidic bond system in the iminomethylenephosphoranes.Im Zusammenhang mit Arbeiten zur Stabilisierung und zum Reaktionsverhalten von Phosphor-Stickstoff-Verhindungen mit sp'-hybridisiertem Phosphorz), insbesondere den Untersuchungen an Diiminoph~sphoranen~), interessierte uns das System Iminophosphan/Diazoalkan. In einer vorlaufigen Mitteilung berichteten wir iiher die Reaktion von [Bis(trimethylsilyl)-amino](trimethylsilylimino)phosphan (1) und a-alkylierten Diazoethanen (2 -5), die unter N2-

Die thermische Umlagerung des N‐alkylierten Amino(imino)phosphorans (1) in den Dreiring (2) ist eine überraschende Reaktion, denn N‐silylierte Analoga von (1) bilden durch 1,3‐Silylgruppenverschiebung Diiminophosphorane. (R=iPr, R′ = tBu)

Durch Umsetzung des Methylenphosphins (I) mit einem Äquival.