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)] with S were strongly dependent on experimental conditions (R* = 2,4,6-CHBu). When using 1 equiv of sulfur, complex [MoReCp(μ-η:κ-SPR*)(CO)] was slowly formed at 313 K, with a thiophosphinidene ligand unexpectedly bridging the dimetal center in the novel μ-κ:η coordination mode, as opposed to the μ-κ:η mode usually found in related complexes. The latter underwent fast decarbonylation at 363 K to give [MoReCp(μ-η:η-SPR*)(CO)], with a six-electron donor thiophosphinidene ligand rearranged into the rare μ-η:η 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-η:κ-SPR*)(CO)], its dithiophosphonite-bridged isomer [MoReCp(μ-κ:κ-SPR*)(CO)], or the trithiophosphonate-bridged derivative [MoReCp(μ-κ:κ-SPR*)(CO)], all of them displaying novel coordination modes of their PRS and PRS ligands, as determined by X-ray diffraction studies. In contrast, the related MoMn complex yielded [MoMnCp(μ-η:η-SPR*)(CO)] 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-η:η-SePR*)(CO)] (M = Re, Mn), these providing a new coordination mode for selenophosphinidene ligands.