The synthesis and molecular structures of the crystalline 1-aza-2-phospha(V)allyllithium compounds [Li(LL ′ )(OEt2)2] and [Li(LL ′ )]2 [LL ′ = CH(SiMe3)P(Ph)2NSiMe3] and the preparation and characterisation of the new phosphinimines CH(R1)(R2)P(Ph)2 NSiMe3 [R1 = R2 = SiMe3; R1 = H, R2 = Si(Me)2NEt2] †

Abstract

Reaction of CH2(SiMe3)P(Ph)2NSiMe3 (HLL′) I with LiBun afforded, after recrystallisation from diethyl ether, [Li{CH(SiMe3)P(Ph)2NSiMe3}(OEt2)2]. Removal of the co-ordinating Et2O molecules in vacuo and subsequent recrystallisation from hexane yielded the solvent-free dimeric lithium complex [Li{CH(SiMe3)P(Ph)2NSiMe3}]2. The crystal structures of the crystalline compounds [Li(LL′)(OEt2)2] and the fused dinuclear [Li(LL′)]2 are reported. Each contains a planar Li(LL′) ring. The Li(2)–N bond of the Li(LL′) moiety of the latter is also part of a six-membered Li(2)–N–Li(1)–N–P–C ring, planar except for Li(2); the two Li atoms are bridged by a second [LL′]– ligand, so that the bridgehead lithium atom Li(2) is bound to the allyl carbon of each [LL′]– ligand, whereas Li(1) is bound to two nitrogen atoms. In toluene-d8, this compound shows singlet 7Li-{1H} and 31P-{1H} NMR spectral signals, even at low temperatures. Its reaction with Me3SiO3SCF3 afforded the phosphinimine CH(SiMe3)2P(Ph)2 NSiMe3 (HLL″) II, a potential precursor for a new 1-aza-2-phospha(V)allyl ligand, as was shown by its straightforward lithiation to yield Li(LL″). The novel phosphinimine CH2{SiMe2(NEt2)}P(Ph)2NSiMe3 (HLL‴) III was synthesized by reaction of Li[CH2P(Ph)2NSiMe3] with Et2NSi(Me)2Cl and, similar to the lithiation of II, reaction of III with LiBun afforded Li(LL‴) in high yield.