Amidophosphine-borane complexes of alkali metals and the heavier alkaline-earth metals: Syntheses and structural studies

摘要

The N-benzhydrylamido-1,1-diphenylphosphine-borane ligand [Ph _2P(BH_3)NH(CHPh_2)] (1-H) has been prepared via the reaction of an equimolar ratio of the phosphine amine [Ph _2PNH(CHPh_2)] and the borane adduct [BH_3· SMe_2] at an ambient temperature. The reaction of 1-H with ((trimethylsilyl)methyl)lithium (neosilyllithium), [LiCH_2SiMe _3], afforded a three-membered lithium amidophosphine-borane complex with the composition ([η~2-Ph_2CHNP(BH _3)Ph_2)Li(THF)_2] (2). Analogous reactions with sodium and potassium bis(trimethylsilyl)amides at ambient temperature yielded the respective alkali-metal amidophosphine-borane complexes [{(Ph _2CHNP(BH_3)Ph_2)Na(THF)_2} _2] (3) and [{(Ph_2CHNP(BH_3)Ph _2)K(THF)_2}_2] (4), with the loss of hexamethyldisilazane, [(Me_3Si)_2NH]. The corresponding heavier alkaline-earth-metal complexes [M(THF)_2{Ph _2P(BH_3)N(CHPh_2)}_2] (M = Ca (5), Sr (6), Ba (7)) can be obtained via the reaction of [M{N(SiMe_3) _2}_2(THF)_n] (M = Ca, Sr, Ba) and 1-H. The metal complexes 5-7 can also be prepared via a salt metathesis route, where the alkali-metal salts 3 and 4 were reacted with the respective metal diiodides in THF at ambient temperature. The molecular structures of 1-H and 2-7 have been established by X-ray diffraction analyses, and from the solid-state structures of 3-7, it was confirmed that, in all of the compounds, the metal ions are chelated through the nitrogen atom and the hydrogen atoms of the borane group of ligand 1-H.