Snapshots of sequential polyphosphide rearrangement upon metallatetrylene addition

Insertion and functionalization of gallasilylenes [L$^{Ph}$Si–Ga(Cl)L$^{BDI}$] (L$^{Ph}$ = PhC(NtBu)$_{2}$; L$^{BDI}$ = [{2,6-iPr$_{2}$C$_{6}$H$_{3}$NCMe}$_{2}$CH]) into the cyclo-E$_{5}$ rings of [Cp*Fe(η$^{5}$-E$_{5}$)] (Cp* = η$^{5}$-C$_{5}$Me$_{5}$; E = P, As) are reported. Reactions of [Cp*Fe(η$^{5}$-E$_{5}$)] with gallasilylene result in E–E/Si–Ga bond cleavage and the insertion of the silylene in the cyclo-E$_{5}$ rings. [(L$^{Ph}$Si-Ga(Cl)L$^{BDI}$){(η$^{4}$-P$_{5}$)FeCp*}], in which the Si atom binds to the bent cyclo-P$_{5}$ 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(η$^{5}$-As$_{5}$)] with the heavier gallagermylene [LL$^{Ph}$Ge–Ga(Cl)L$^{BDI}$B] 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.