We report on the synthesis and characterization of mixed pnictogenylboranes. The substitution of the Lewis base SMe₂ in (OC)₅W–PH₂BH₂–SMe₂ (2) by different pnictogenylboranes ER₂BH₂–LB (E=P, As, Sb) leads to the Lewis acid/base stabilized butane analogue (OC)₅W–PH₂BH₂ER₂BH₂–LB (3 a, b: E=P; R=H, SiMe₃; LB=NMe₃; 4 a, b: E=As; R=H, SiMe₃; LB=NMe₃; 5: E=Sb; R=SiMe₃; LB=NHC^Me). All of these compounds were characterized by single-crystal X-ray structure analysis, mass spectrometry, NMR, and IR spectroscopy. In addition, the very unstable phosphanylborane chain PH₂BH₂PH₂BH₂–NMe₃ (1) was synthesized. DFT calculations provide insight into the thermodynamics of these reactions.