Formation of a Hexaphosphido Cobalt Complex through P−P Condensation

The reaction between diphosphorus derivatives [(ClImDipp)P2(Dipp)]OTf (1[OTf]) and [(ClImDipp)P2(Dipp)Cl] (1[Cl]) with the cyclotetraphosphido cobalt complex [K(18c‐6)][(PHDI)Co(η4‐cyclo‐P4)] (2) leads to the formation of complex [(PHDI)Co{η4‐cyclo‐P6(Dipp)(ClImDipp)}] (3), which features an unusual hexaphosphido ligand [ClImDipp=4,5‐dichloro‐1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐yl, Dipp=2,6‐diisopropylphenyl, 18c‐6=18‐crown‐6, PHDI=bis(2,6‐diisopropylphenyl)phenanthrene‐9,10‐diimine]. Complex 3 was obtained as a crystalline material with a moderate yield at low temperature. Upon exposure to ambient temperature, compound 3 slowly transforms into two other compounds, [K(18c‐6)][(PHDI)Co(η4‐P7Dipp)] (4) and [(PHDI)Co{cyclo‐P5(ClImDipp)}] (5). The novel complexes 3–5 were characterized using multinuclear NMR spectroscopy and single‐crystal X‐ray diffraction. To shed light on the formation of these compounds, a proposed mechanism based on 31P NMR monitoring studies is presented. [4+2] condensation reaction of diphosphene [(ClImDipp)P2(Dipp)]OTf and diphosphanide [(ClImDipp)P2(Dipp)Cl] with the cyclo‐P4 cobalt complex [K(18c‐6)][(PHDI)Co(η4‐cyclo‐P4)] forms a CoP6 complex, featuring an unusual hexaphosphido ligand composed of a cyclo‐P5 ring and an exocyclic (ClImDipp)P moiety. 31P NMR spectroscopic studies reveal that at ambient temperature, this CoP6 complex undergoes disproportionation into more stable CoP7 and CoP5 complexes.