Reactions of RSe− (R = Me,Ph) Groups in [RSeFe(CO)4I and [RSeCr(CO)5−]

The anionic MeSeFe(CO)₄] and MeSeCr(CO)₅] complexes were synthesized by reaction of PPN]HFe(CO)₄] and PPN]HCr(CO)₅] with MeSeSeMe respectively via nucleophilic cleavage of the Se-Se bond. The ease of cleavage of the Se-Se bond follows the nucleophilic strength of metal-hydride complexes. Methylation of RSeCr(CO)₅^?] by the soft alkylating agent MeI resulted in the formation of neutral (MeSeMe)Cr(CO)₅ in THF at 0°C. In contrast, the ICr(CO)₅^?] was isolated at ambient temperature. Reaction of MeSeFe(CO)₄^?] or MeSeCr(CO)₅^?] with HBF₄ yielded (CO)₃Fc(μ-SeMe)₂Fe(CO)₃ dimer and anionic (CO )₅Cr (μ-SeMe)Cr(CO)₅^?] respectively, and no neutral (HSeMe)Fe(CO)₄ and (HSeMe)Cr(CO)₅ were detected spectrally (IR) even at low temperature. Reaction of NOBF₄ or Ph₃C]BF₄] and MeSeCr(CO)₅^?] resulted in the neutral monodentate (MeSeSeMe)Cr(CO)₅ complex. Addition of 1 equiv CpFe(CO)₂I to 2 equiv MeSeCr(CO)₅^?] gave CpFe(CO)₂(SeMe) and the anionic (CO)₅Cr(μ-SeMe)Cr(CO)₅^?] in THF at ambient temperature.