Cobalt‐Mediated [3+1] Fragmentation of White Phosphorus: Access to Acylcyanophosphanides

Abstract

Despite the accessibility of numerous transition metal polyphosphido complexes through transition‐metal‐mediated activation of white phosphorus, the targeted functionalization of Pn ligands to obtain functional monophosphorus species remains challenging. In this study, we introduce a new [3+1] fragmentation procedure for cyclo‐P4 ligands, leading to the discovery of acylcyanophosphanides and ‐phosphanes. Treatment of the complex [K(18c‐6)][(Ar*BIAN)Co(η4‐P4)] ([K(18c‐6)]3, BIAN = 1,2‐bis(arylimino)acenaphthene diimine) with acyl chlorides results in the formation of acylated tetraphosphido complexes [(Ar*BIAN)Co(η4‐P4C(O)R)] (R = tBu, Cy, 1‐Ad, Ph; 4a‐d). Subsequent reaction of 4a‐d with cyanide salts yields acylated cyanophosphanides [RC(O)PCN]− (9a‐d−) and the cyclo‐P3 cobaltate anion [(Ar*BIAN)Co(η3‐P3)(CN)]− (8−). Further reactions of 4a‐d with trimethylsilyl cyanide (Me3SiCN) and isocyanides provide insight into a plausible mechanism of this [3+1] fragmentation reaction, as these reagents partially displace the P4C(O)R ligand from the cobalt center. Several potential intermediates of the [3+1] fragmentation were characterized. Additionally, the introduction of a second acyl substituent was achieved by treating [K(18c‐6)]9b with CyC(O)Cl, resulting in the first bis(acyl)monocyanophosphine (CyC(O))2PCN (10).