Benzyl Ether-Substituted Phosphido-Borane Complexes of the Alkali Metals

Reduction of {(Me3Si)2CH}PCl(C6H4-2-CH2OMe) withLiAlH4, followed by reaction with BH3 center dot SMe2, gives the phosphaneborane {(Me3Si)2CH}PH(BH3)(C6H4-2-CH2OMe) (2) in good yield. Compound 2 undergoes rapid deprotonation on treatment with nBuLi, PhCH2Na or PhCH2K to give the corresponding alkali metal phosphidoborane complexes [[{(Me3Si)2CH}P(BH3)(C6H4-2-CH2OMe)]ML]2 [ML = Li(THF) (3), Na(tmeda) (4), K(pmdeta) (5)] after crystallization in the presence of the respective co-ligand L. The exact binding mode of the phosphidoborane ligand depends on the nature of the metal center in each case. However, all three alkali metal complexes crystallize as discrete dimers exhibiting MP, MO and M...BH3 contacts.