Alkalimetall‐Phosphaniminate. Neue Synthesen und die Kristallstrukturen von [RbNPPh3]6 und [CsNPPh3]4

Alkali Metal Phosphoraneiminates. New Syntheses and Crystal Structures of [RbNPPh₃]₆ and [CsNPPh₃]₄ The alkali‐metal phosphoraneiminates MNPPh₃ with M = Na, K, Rb, Cs have been synthesized by reactions of Ph₃PI₂ with the alkali‐metal amides in liquid ammonia and were obtained as pure samples by subsequent extraction with toluene. The ethyl derivative KNPEt₃ has been prepared by an analogous route from Et₃PBr₂ and extraction with hexane. Single crystals of the phosphoraneiminates of rubidium and cesium are obtainable by crystallization from toluene and toluene/hexane, respectively. They were suitable for crystal structure determinations. [RbNPPh₃]₆ · 4¹/₂ toluene ( 1 ): space group P1, Z = 2, lattice dimensions at 193 K: a = 1525.5(2); b = 1902.9(2); c = 2178.3(2) pm; α = 95.435(12)°; β = 91.145(12)°; γ = 90.448(12)°; R₁ = 0.0529. The compound forms a Rb₆N₆ skeleton of a double cube with a common face of two rubidium and two nitrogen atoms, the latter being fivefold coordinated by four rubidium atoms and the phosphorus atom. [CsNPPh₃]₄ · 2 toluene · 3³/₄ hexane ( 2 a ): space group Fd3, Z = 8, lattice dimensions at 123 K: a = b = c = 2679.7(1) pm; R₁ = 0.0405. [CsNPPh₃]₄ · 2 toluene ( 2 b ): space group P2₁/n, Z = 4, lattice dimensions at 193 K: a = 1418.9(1); b = 2258.9(1); c = 2497.6(1) pm; β = 91.055(6)°; R₁ = 0.0278. Both cesium compounds form Cs₄N₄ heterocubane structures which are different by means of the packing and by different bond angles at the cesium and nitrogen atoms.