Beschreibung:
<jats:title>Abstract</jats:title><jats:p>High molar weight polyphosphinoboranes represent materials with auspicious properties, but their preparation requires transition metal‐based catalysts. Here, calix[4]pyrrolato aluminate is shown to induce the dehydropolymerization of phosphine boranes to high molar mass polyphosphinoboranes (up to <jats:italic>M</jats:italic><jats:sub>n</jats:sub>=43 000 Da). Combined GPC and <jats:sup>31</jats:sup>P DOSY NMR spectroscopic analyses, quantum chemical computations, and stoichiometric reactions disclose a P−H bond activation by the cooperative action of the square‐planar aluminate and the electron‐rich ligand framework. This first transition metal‐free catalyst for P−B dehydrocoupling overcomes the problem of residual <jats:italic>d</jats:italic>‐block metal impurities in the resulting polymers that might interfere with the reproducibility of the properties for this emerging class of inorganic materials.</jats:p>