Lewis Base Stabilized Phosphanylborane



The abstraction 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[BOND]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[BOND]PH2[BOND]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.