The reaction behavior of [Cp*Fe(η5-As5)] (I)
(Cp*=C5Me5) towards carbenes and their heavier
analogs was investigated. The reaction of I with NHCs
(NHCs=N-heterocyclic carbenes) results in the first
substitution products of polyarsenic ligand complexes by
NHCs [Cp*Fe(η4-As5NHC)] (1 a: NHC=IMe=1,3,4,5-
tetramethylimidazolin-2-ylidene, 1b: NHC=IMes=1,3-
bis(2,4,6-trimethylphenyl)-imidazolin-2-ylidene). In contrast,
the reaction of I with EtCAAC (EtCAAC=2,6-
diisopropylphenyl)-4,4-diethyl-2,2-dimethyl-pyrrolidin-
5-ylidene) leads to a fragmentation and the formation of
an unprecedented As6-sawhorse-type compound [As2-
(AsEtCAAC)4] (2). The reaction of (LE)2 (L=PhC-
(NtBu)2; E=Si, Ge) with I resulted in a rearrangement
and an insertion of LE fragments, forming unique
silicon- (4: [Cp*Fe(η4-As4SiL)], 5a: [Cp*Fe(η4-As6SiL))
and germanium-containing (5b: [Cp*Fe(η4-As6GeL))
cyclic polyarsenic ligand complexes