Reactions of Heterometallic Phosphinidene-Bridged MoMn and MoRe Complexes with Sulfur and Selenium: From Chalcogenophosphinidene- to Trithiophosphonate-Bridged Derivatives

Reactions of [MoReCp­(μ-PR*)­(CO)6] with S8 were strongly dependent on experimental conditions (R* = 2,4,6-C6H2tBu3). When using 1 equiv of sulfur, complex [MoReCp­(μ-η2:κ1S-SPR*)­(CO)6] was slowly formed at 313 K, with a thiophosphinidene ligand unexpectedly bridging the dimetal center in the novel μ-κ1S:η2 coordination mode, as opposed to the μ-κ1P:η2 mode usually found in related complexes. The latter underwent fast decarbonylation at 363 K to give [MoReCp­(μ-η2:η2-SPR*)­(CO)5], with a six-electron donor thiophosphinidene ligand rearranged into the rare μ-η2:η2 coordination mode. Depending on reaction conditions, reactions with excess sulfur involved the addition of two or three S atoms to the phosphinidene ligand to give new complexes identified as the dithiophosphinidene-bridged complex [MoReCp­(μ-η2:κ2S,S′-S2PR*)­(CO)5], its dithiophosphonite-bridged isomer [MoReCp­(μ-κ2S,S′:κ2S,S′-S2PR*)­(CO)5], or the trithiophosphonate-bridged derivative [MoReCp­(μ-κ2S,S′:κ2S,S′-S3PR*)­(CO)5], all of them displaying novel coordination modes of their PRS2 and PRS3 ligands, as determined by X-ray diffraction studies. In contrast, the related MoMn complex yielded [MoMnCp­(μ-η2:η2-SPR*)­(CO)5] under most conditions. A similar output was obtained in reactions with gray selenium for either MoRe or MoMn phosphinidene complexes, which under different conditions only gave the pentacarbonyl complexes [MoMCp­(μ-η2:η2-SePR*)­(CO)5] (M = Re, Mn), these providing a new coordination mode for selenophosphinidene ligands.