Chemistry of polyfunctional molecules CXXX. Rubidium and caesium bis(diphenylphosphanyl)amide - Syntheses, 18-crown-6 complexes, cleavage products, crystal structures, and solid state NMR spectra [German]

摘要

The metalation of bis(diphenylphosphanyl)amine, HN(PPh2)(2) (5), with RbOtBu in the presence of N,N,N',N ",N "-pentamethyldiethylenetriamine (PMDTA (3)) in toluene surprisingly affords the nearly PMDTA free RbN(PPh2)(2) (6a). Recrystallization of 6a from tetrahydrofuran (THF) yields RbN(PPh2)(2).0.5 THF (6b). Compounds 6a, b crystallize in thin needles; however, these are not suitable for X-ray structure analyses. The reactions of 5 with MOtBu (M = Rb, Cs) in the presence of 18-crown-6 in toluene yield the monomeric, pale yellow rubidium and caesium complexes [Rb(18-crown-6)(N(PPh2)(2))] (7) and [Cs(18-crown-6)(N(PPh2)(2))] (8), respectively. Allowing to stand a solution of 8 in THF for three months at 20 degrees C results in a cleavage product of 8. This is identified as the dimeric yellow complex [(Cs(18-crown-6))(2)(mu-N=P(H)Ph-2)(2)].THF (9). The source of the hydrogen atom in the bridging phosphorane iminate anion [[N=P(H)Ph-2](-) is uncertain. Compounds 7-9 are structurally characterized by X-ray analyses. These reveal that [N(PPh2)(2)](-) acts as P-ligating chelate in 7, whereas it coordinates the Cs+ as N-donor as well as eta(2) C-donor with one phenyl group in 8. No phosphorus coordination is observed in 8. The two caesium cations in 9 are two-fold N-bridged by [[N=P(H)Ph-2]. The coordination sphere of each caesium atom is completed by a 18-crown-6 ligand. The solid state C-13 NMR spectrum of 8 reveals dynamic phenomena (rotation of the 18-crown-6 ligand). In the solid state P-31 spectrum of 8, (31)p, (31)p-J-coupling is observed between the chemically non-equivalent phosphorus sites (J = 390 Hz). [References: 55]