Electrophilic Functionalization of a Hexaphosphabenzene Ligand in [(Cp*Mo)2(μ,η6 : 6-P6)]

Abstract

The electrophilic functionalization of the triple-decker sandwich complex [{Cp*Mo}₂(μ,η^6:6-P₆)] (A) and its mono-oxidized counterpart [{Cp*Mo}₂(μ,η^6:6-P₆)][SbF₆] (B) with reactive main-group electrophiles as well as radical scavengers is shown to be a reliable method for the selective functionalization of the hexaphosphabenzene ligand. Depending on the electrophile used, the regioselectivity of the functionalization can be adjusted. Using group 16 electrophiles, the trisubstituted compounds [{Cp*Mo}₂{(μ,η^{3 : 3}-P₃)(μ,η^{1 : 1 : 1 : 1}-1,3-(SePh)₂-2-Br-P₃)}][TEF] (1), [{Cp*Mo}₂(μ,η^{3 : 3}-P₃)(μ,η^{1 : 1 : 1 : 1}-1,2,3-(EPh)₃-P₃)][SbF₆] (E=S (2), Se (3)) as well as the side product [{Cp*Mo}₂(μ,η^4:4-P₄)(μ,η^{1 : 1}-P(SPh)₂)][SbF₆] (4) are obtained. By switching to phosphenium ions as group 15 electrophiles, the ring-inserted products [{Cp*Mo}₂(μ,η^{3 : 3 : 2 : 2}-P₇R₂)][TEF] (R=Cy (5), ⁱPr (6)) are isolated, showing an unprecedented P₇R₂ structural motif. Furthermore, the reaction with MeOTf yields the dimeric [{Cp*Mo}₄(1,4-Me₂-μ₄,η^{1 : 1 : 1 : 1 : 1 : 1}-P₆)(μ,η^{3 : 3}-P₃)₂][TEF]₂ (7) as the first example of a complex featuring two interconnected cyclo-P₆ middle deck ligands. Finally, by combination of the methylation step with Ph₂Se₂, the mixed group 14/16 complex [{Cp*Mo}₂{(μ,η^{3 : 3}-P₃)(μ,η^{1 : 1 : 1 : 1}1,2-(SePh)₂-3-Me-P₃)}][OTf] (8) is obtained.

Keywords: chalcogens; electrophilic substitution; molybdenum; phosphorus; triple decker complexes.