Reactivity of P4 butterfly complexes towards NHCs - generation of a metal-bridged P2 dumbbell complex.

The reactivity of the P4 butterfly complexes [{Cp'''Fe(CO)2}2(μ,η1:1-P4)] (A, Cp''' = C5H2tBu3) and [{Cp*Cr(CO)3}2(μ,η1:1-P4)] (B, Cp* = C5(CH3)5) towards the N-heterocyclic carbene IMe (1,3,4,5-tetramethyl-imidazol-2-ylidene) is reported. The reaction of A affords [P(IMe)2][Fe(CO)2Cp'''] (1) or [P(IMe)2][{Cp'''Fe}2(μ,η3:3-P3)] (2), the latter possessing a P3-allylic moiety. In contrast, the reaction of B yields [P(IMe)2][Cr(CO)3Cp*] (3) and [{Cp*Cr(CO)2}(η2-P2IMe2)][Cr(CO)3Cp*] (4), featuring a novel metal-bridged P2 dumbbell.