Abstract The reaction of tris(bromo-tert-butylphosphino)phosphane, P(t-BuPBr)3, with lithium aluminium hydride leads to the title compound P(t-BuPH)3 (1), which could be isolated in a pure state. 1 is the first partially substituted derivative of iso-tetraphosphane(6), P(PH2)3, and was characterized in all details. Because of the chirality of the Z-BuPHgroups, 1 forms two diastereomers with RRS(SSR)- and RRR(SSS)-configuration in a ratio of about 3:1. The conformation of both isomers, which could be deduced from the 31P NMR parameters, is mainly determined by the steric situation of the molecule.

Kleine Mengen des linearen Triphosphindiiodids (I) werden mit einem Überschuß an LiH unter Bildung des Cyclotriphosphins (II) nahezu quantitativ dehalogeniert.

tBu6P8 (1) and tBu6As8 (2) do not have analogous structures. That (1) has two P4-rings linked to each other and not a pentalene-type framework like (2) (and Me6P8, Et6P8 and iPr6P8) is ascribed to the strong transannular interaction of the tBu groups.

Abstract Tri-tert-butyl-cyclotriphosphane is obtained by the dehalogenation of 1,3-diiodo-1,2,3-tri-tert-butyl-triphosphane with lithiumhydride. This reaction represents a so far unknown type of ring-closure leading to cyclotriphosphanes, which corresponds to the classical synthesis of cyclopropanes starting from 1,3-dichloropropanes.

Nicht die erwartete analoge Struktur haben tBu6P8 (1) und tBu6As8 (2). Daß (1) zwei miteinander verbundene P4‐Ringe bildet und nicht wie (2) (und Me6P8, Et6P8 und iPr6P8) ein pentalenartiges Gerüst hat, wird auf die starke transanulare Wechselwirkung der tBu‐Gruppen zurückgeführtmagnified image.

Tricyclohexyl-cyclotriphosphane, (c-C6H11P)3 (1), is another relatively stable compound with a three membered phosphorus ring. It is produced in the reactions of (a) K2(c-C6H11P)4 with CH2Cl2, (b) K2(c-C6H11P)4 with CS2, (c) c-C6H11PCl2 with sodium in dioxane. The following by-products are formed: (c-C6H11P)4CH2 (3), (c-C6H11P)5 (2) and (c-C6H11P)4 in the reaction (a); mainly (c-C6H11P)4 in the reaction (b); (c-C6H11P)5 (2) and (c-C6H11P)4 in the reaction (c). The P3 ring compound 1 and the P5 ring compound 2 can be isolated in a pure state. The oligomers (c-C6H11P)n, n = 3, 4, 5, clearly are distinguished by the melting points, the molecular masses and by the 31P NMR and vibrational spectra. The 31P NMR parameters of 3 are reported. The cyclohexyl groups in 1, 2 and 3 are situated on both sides of the corresponding ring systems, giving rise to a maximum number of “trans” orientated neighboring substituents.