Ring Contraction by NHC‐Induced Pnictogen Abstraction

The reaction of [Cp′′′Co(η 4 ‐P 4 )] ( 1 ) (Cp′′′=1,2,4‐tBu 3 C 5 H 2 ) with Me NHC ( Me NHC=1,3,4,5‐tetramethylimidazol‐2‐ylidene) leads through NHC‐induced phosphorus cation abstraction to the ring contraction product [( Me NHC) 2 P][Cp′′′Co(η 3 ‐P 3 )] ( 2 ), which represents the first example of an anionic CoP 3 complex. Such NHC‐induced ring contraction reactions are also applicable for triple‐decker sandwich complexes. The complexes [(Cp*Mo) 2 (μ,η 6:6 ‐E 6 )] ( 3 a , 3 b ) (Cp*=C 5 Me 5 ; E=P, As) can be transformed to the complexes [( Me NHC) 2 E][(Cp*M) 2 (μ,η 3:3 ‐E 3 )(μ,η 2:2 ‐E 2 )] ( 4 a , 4 b ), with 4 b representing the first structurally characterized example of an NHC‐substituted As I cation. Further, the reaction of the vanadium complex [(Cp*V) 2 (μ,η 6:6 ‐P 6 )] ( 5 ) with Me NHC results in the formation of the unprecedented complexes [( Me NHC) 2 P][(Cp*V) 2 (μ,η 6:6 ‐P 6 )] ( 6 ), [( Me NHC) 2 P][(Cp*V) 2 (μ,η 5:5 ‐P 5 )] ( 7 ) and [(Cp*V) 2 (μ,η 3:3 ‐P 3 )(μ,η 1:1 ‐P{ Me NHC})] ( 8 ).