Reactivity of [Cp*Fe(η⁵ ‐As₅)] towards Carbenes, Silylenes and Germylenes

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, 1 b: 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)], 5 a: [Cp*Fe(η4-As6SiL)) and germanium-containing (5 b: [Cp*Fe(η4-As6GeL)) cyclic polyarsenic ligand complexes.