Metal Complexes (M = Zn, Sn, and Pb) of 2-Phosphinobenzenethiolates: Insights into Ligand Folding and Hemilability

The divalent metal complexes MII{(SC6H4-2-PR2)-κ2S,P}2 (3–7, and 9–11) (M = Zn, Sn, or Pb; R = iPr, tBu, or Ph), the Sn(IV) complexes Sn{(SC6H4-2-PR2)-κ2-S,P}Ph2Cl (12 and 13) (R = iPr and tBu), and the ionic Sn(IV) complexes [Sn{(SC6H4-2-PR2)-κ2-S,P}Ph2][BPh4] (14 and 15) (R = iPr and tBu) have been prepared and characterized by multinuclear NMR spectroscopy and single crystal X-ray diffraction when suitable crystals were afforded. The Sn(II) and Pb(II) complexes with R = Ph, iPr, or tBu (5, 6, 9, and 10) demonstrated ligand “folding” hinging on the P,S vector—a behavior driven by the repulsions of the metal/phosphorus and metal/sulfur lone pairs and increased M-S sigma bonding strength. This phenomenon was examined by density functional theory (DFT) calculations for the compounds in both folded and unfolded states. The Sn(IV) compound 13 (R = tBu) crystallized with the phosphine in an axial position of the pseudotrigonal bipyramidal complex and also exhibited hemilability in the Sn–P dative bond, while ...