High Spin Iron–Phosphinidene and Arsinidene Complexes With Attenuated Metal–Ligand Multiple Bond Character

The MEH 2 salts (M = Na, K; E = P, As) react with high spin ( S = 2) PhB(AdIm) 3 FeCl (PhB(AdIm) 3 – = tris(3‐adamantylimidazol‐2‐ylidene)phenylborate) to afford the corresponding PhB(AdIm) 3 FePH 2 and PhB(AdIm) 3 FeAsH 2 complexes. Remarkably, these complexes can be deprotonated by benzyl potassium in the presence of equimolar 18‐crown–6 or 2,2,2‐crypt to provide the parent phosphinidene and arsinidene complexes, [PhB(AdIm) 3 FePH] – and [PhB(AdIm) 3 FeAsH] – . Structural and spectroscopic characterization, combined with computational investigations, provide evidence for multiconfigurational electronic structures in which the metal–ligand multiple bond character is attenuated by the high spin iron(II) center. Initial reactivity studies reveal the nucleophilic character of the pnictogenidene ligands, which provide phosphinophosphinidene and phosphinoarsinidene products with a chlorodiazaphospholidine electrophile.