From neutral to anionic eta1-carbon ligands: experimental synthesis and theoretical analysis of a rhodium-yldiide complex.

Deprotonation of a cationic rhodium complex of a chelating semistabilized phosphino-phosphonium sulfinyl-ylide ligand afforded the neutral complex of the corresponding yldiide ligand. Despite the limited stability of the yldiide complex its structure was ascertained by ESI MS and multinuclear (1)H, (31)P, (13)C, and (103)Rh NMR spectroscopy. DFT calculations were carried out at the B3PW91/6-31G*/LANL2DZ*(Rh) level to derive a reasonable gas-phase structure for the yldiide complex or model thereof and gain insight into their electronic structure. ELF and AIM topological analyses were used to investigate the metal-ligand bonding and estimate the electron transfer resulting from proton abstraction. ELF weighting of the resonance forms of the anionic "free" yldiide ligand (Ar(3)PC(-)-S(O)Ar) was compared to the corresponding weighting of previously reported neutral counterparts (XCY), namely, bis-alpha-zwitterionic bisylides of phosphonium, sulfonium, or iminosulfonium moieties (X, Y = PR(3), SR(2), S(NMe)R(2)). The results suggest that the phosphonium sulfinylyldiide can be regarded as a tris-alpha,beta-zwitteranionic bisylide (Ar(3)P(+)-C(2-)-S(+)(-O(-))p-Tol).