REACTIONS OF RSE- (R=ME,PH) GROUPS IN [RSEFE(CO)4-] 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-degrees-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)3Fe(mu-SeMe)2Fe(CO)3 dimer and anionic [(CO)5Cr(mu-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(mu-SeMe)Cr(CO)5-] in THF at ambient temperature.