The Stabilisation of Monomeric Parent Compounds of Phosphanyl- and Arsanylboranes

The structures of the parent compounds of phosphanyl‐ and arsanylboranes, H2BPH2 and H2BAsH2, were calculated by DFT‐B3LYP methods. Such compounds have not previously been obtained preparatively. By applying the concept of Lewis acid/base stabilisation, [(CO)5W(H2EBH2⋅NMe3)] (E=P (3), As (4)) derivatives have been synthesised by the metathesis reactions between Li[(CO)5WEH2] and ClH2BNMe3 (E=P, As). Comprehensive thermodynamic studies on these systems verify the high stability of the Lewis acid/base stabilised complexes. Unexpected based on the thermodynamic calculations, UV radiation of the phosphanylborane 3 leads to the dinuclear phosphanido‐bridged complex [(CO)8W2(μ‐PHBH2⋅NMe3)2] (5) by H2 and CO elimination. The parent compounds of phosphanyl‐ and arsanylboranes of type A have not yet been synthesised or even detected in matrix isolation experiments. Metathesis reactions between Li[(CO)5WEH2] and ClH2B⋅NMe3 (E=P, As) have for the first time provided a route to Lewis acid/base stabilised complexes of the type B. Comprehensive DFT calculations on these systems verify the high stability of the complexes of type B.