Metal complexes (M = Zn, Sn, and Pb) of 2-phosphinobenzenethiolates: Insights into ligand folding and hemilability

Article abstract of DOI:10.1021/ic400990n

The divalent metal complexes M^II{(SC₆H ₄-2-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{(SC₆H ₄-2-PR₂)-κ²-S,P}Ph₂][BPh ₄] (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 compound 12 (R = ⁱPr), interestingly, crystallized with phosphine in an equatorial position and did not show hemilability. Finally, the crystal structure of 15 (R = ^tBu) revealed the presence of an uncommon, 4-coordinate, stable Sn(IV) cation.