Lewis Base Stabilized Phosphanylborane

The ion of the Lewis acid from [W(CO)5(PH2BH2⋅NMe3)] (1) by an excess of P(OMe3)3 leads to the quantitative formation of the first Lewis base stabilized monomeric parent compound of phosphanylborane [H2PBH2⋅NMe3] 2. Density functional theory (DFT) calculations have shown a low energetic difference between the crystallographically determined antiperiplanar arrangement of the lone pair and the trimethylamine group relative to the PB core and the synperiplanar conformation. Subsequent reactions with the main‐group Lewis acid BH3 as well as with an [Fe(CO)4] unit as a transition‐metal Lewis acid led to the formation of [(BH3)PH2BH2⋅NMe3] (3), containing a central H3BPH2BH2 unit, and [Fe(CO)4(PH2BH2⋅NMe3)] (4), respectively. In oxidation processes with O2, Me3NO, elemental sulfur, and selenium, the boranylphosphine chalcogenides [H2P(Q)BH2⋅NMe3] (Q = S 5 b; Se 5 c) as well as the novel boranyl phosphonic acid [(HO)2P(O)BH2⋅NMe3] (6 a) are formed. All products have been characterized by spectroscopic as well as by single‐crystal X‐ray structure analysis. The first monomeric compound of phosphanylborane [H2PBH2⋅NMe3] (2), stabilized only by a Lewis base, has been synthesized, opening broader perspectives for subsequent reactions. Thus, reactions with different Lewis acids, novel main‐group elements, or transition‐metal‐substituted phosphanylboranes become possible. In detailed studies, oxidation processes yielded boranylphosphine chalcogenides [H2P(Q)BH2⋅NMe3] (Q = S; Se) as well as a novel boranyl phosphonic acid [(HO)2P(O)BH2⋅NMe3].