Snapshots of sequential polyphosphide rearrangement upon metallatetrylene addition

Insertion and functionalization of gallasilylenes [L^PhSi-Ga(Cl)L^BDI] (L^Ph = PhC(NtBu)₂; L^BDI = [{2,6-iPr₂C₆H₃NCMe}₂CH]) into the cyclo-E₅ rings of [Cp*Fe(η⁵-E₅)] (Cp* = η⁵-C₅Me₅; E = P, As) are reported. Reactions of [Cp*Fe(η⁵-E₅)] with gallasilylene result in E-E/Si-Ga bond cleavage and the insertion of the silylene in the cyclo-E₅ rings. [(L^PhSi-Ga(Cl)L^BDI){(η⁴-P₅)FeCp*}], in which the Si atom binds to the bent cyclo-P₅ ring, was identified as a reaction intermediate. The ring-expansion products are stable at room temperature, while isomerization occurred at higher temperature, and the silylene moiety further migrates to the Fe atom, forming the corresponding ring-construction isomers. Furthermore, reaction of [Cp*Fe(η⁵-As₅)] with the heavier gallagermylene [L^PhGe-Ga(Cl)L^BDI] was also investigated. All the isolated complexes represent rare examples of mixed group 13/14 iron polypnictogenides, which could only be synthesized by taking advantage of the cooperativity of the gallatetrylenes featuring low-valent Si(ii) or Ge(ii) and Lewis acidic Ga(iii) units/entities.