Unprecedented Reaction Mode of Phosphorus in Phosphinidene Rare-Earth Complexes: A Joint Experimental–Theoretical Study

Reactions
of trinuclear rare-earth metal complexes bearing functionalized
phosphinidene ligand [L3Ln3­(μ2-Me)2­(μ3-Me)­(μ3-η1:η2:η2-PC6H4-o)] (L = [PhC­(NC6H4­iPr2-2,6)2]−, Ln = Y (1a),
Lu (1b)) with phenyl­acetylene, CO2,
diisopropyl carbodiimide, isocyanide, or PhSSPh lead to the formation
of a series of phosphorus-containing products. The reaction of 1 with CS2 yields two novel P-methyl-phosphindole-2,3-dithiolate
dianion complexes, revealing an unusual tandem desulfurization/​coupling/​cyclization
reaction mode of CS2. A possible reaction pathway was determined
by density functional theory calculations. This emphasizes the key
role of the reduction power of the formal P2– part
of the phosphinidene in the C–S bond cleavage.