P-H bond activation of primary phosphine-boranes: Access to alpha-hydroxy and alpha,alpha'-dihydroxyphosphine-borane adducts by uncatalyzed hydrophosphination of carbonyl derivatives

Primary P-phenyl and P-methyl phosphine-boranes 1 and 2 are prepared by complexation of the free phosphines with BH3 . SMe2. They are stable and can be purified by distillation. Under basic conditions, they lead selectively to secondary alkylphosphine-boranes and under neutral conditions to the corresponding mono- and bis-hydroxyphosphine-boranes 5 and 6. All these new compounds are purified by chromatography on silica gel. A competitive hydroboration induced by the decomplexation of BH3 is observed as a minor process. Conditions for the decomplexation of phosphine-borane adducts are presented.