Snapshots of sequential polyphosphide rearrangement upon metallatetrylene addition.

Insertion and functionalization of gallasilylenes [L Ph Si-Ga(Cl)L BDI ] (L Ph = PhC(N t Bu) 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 [L Ph Ge-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.