Adducts of diaminophosphines with organoboranes

Abstract

Reactions of chlorodiaminophosphines (R2N)2PCl (R=Et, iPr) with organoborohydrides M[BR′nH4‐n] (M=Na, Li; n=1-3; R′=alkyl, Ph, CN) proceed via H/Cl metathesis to furnish secondary phosphines and boranes which may either combine to afford isolable donor‐acceptor adducts (R2N)2P(H)-BR′nH3‐n, coexist without any sign of mutual interaction, or give rise to mixtures comprising both a labile phosphine borane and its constituents in a temperature dependent equilibrium. Stable phosphine complexes of BH2CN and BH2Ph react with KN(SiMe3)2 under PH‐bond metalation to afford spectroscopically detectable diaminophosphide boranes whose usability as nucleophilic building blocks is illustrated by trapping one specimen in a PC‐bond formation reaction with an alkyl halide. The selectivity of the individual H/Cl‐metathesis and electrophilic substitution steps as well as the thermal stability of the various reaction products depend subtly on the Lewis acidity of the borane fragment and on steric factors. Several complexes of (iPr2N)‐substituted phosphines with cyano‐ and phenylborane were characterized by single‐crystal XRD.