Formation of monomeric Sn(ii) and Sn(iv) perfluoropinacolate complexes and their characterization by 119 Sn Mössbauer and 119 Sn NMR spectroscopies
The synthesis and characterization of a series of Sn(II) and Sn(IV) complexes supported by the highly electron-withdrawing dianionic perfluoropinacolate (pinF) ligand are reported herein. Three analogs of [Sn IV (pin F ) 3 ] 2- with NEt 3 H + (1), K + (2), and {K(18C6)} + (3) counter cations and two analogs of [SnII(pinF)2]2- with K+ (4) and {K(15C5) 2 } + (5) counter cations were prepared and characterized by standard analytical methods, single-crystal X-ray diffraction, and 119 Sn Mössbauer and NMR spectroscopies. The six-coordinate SnIV(pinF) complexes display 119 Sn NMR resonances and 119 Sn Mössbauer spectra similar to SnO 2 (cassiterite). In contrast, the four-coordinate SnII(pinF) complexes, featuring a stereochemically-active lone pair, possess low 119 Sn NMR chemical shifts and relatively high quadrupolar splitting. Furthermore, the Sn(II) complexes are unreactive towards both Lewis bases (pyridine, NEt 3 ) and acids (BX 3 , Et 3 NH + ). Calculations confirm that the Sn(II) lone pair is localized within the 5s orbital and reveal that the Sn 5p x LUMO is energetically inaccessible, which effectively abates reactivity.