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

Abstract

The reaction behavior of [Cp*Fe(η⁵ -As₅ )] (I) (Cp*=C₅ Me₅ ) 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 -As₅ NHC)] (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 ^Et CAAC (^Et CAAC=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 (As^Et CAAC)₄ ] (2). The reaction of (LE)₂ (L=PhC(N^t Bu)₂ ; E=Si, Ge) with I resulted in a rearrangement and an insertion of LE fragments, forming unique silicon- (4: [Cp*Fe(η⁴ -As₄ SiL)], 5 a: [Cp*Fe(η⁴ -As₆ SiL)) and germanium-containing (5 b: [Cp*Fe(η⁴ -As₆ GeL)) cyclic polyarsenic ligand complexes.

Keywords: Arsenic; Functionalization; Germylene; Nucleophiles; Silylene.