Chemistry of a novel family of tridentate alkoxy tin(II) clusters

Article abstract of DOI:10.1021/ja0202309

The chemical interconversions observed for a novel family of trihydroxymethyl ethane (THME-H₃) ligated Sn(II) compounds have been determined using single-crystal X-ray and ¹¹⁹Sn NMR experiments. (μ-THME)₂Sn₃ (1) was isolated from the reaction of 3 equiv of [Sn(NR₂)₂]₂ (R = SiMe₃) with 4 equiv of THME as a unique trinuclear species capped above and below the plane of Sn atoms by two THME ligands. Upon reaction with Sn(NR₂)₂ , compound 1 rearranged to yield another novel molecule [μ-THME)Sn₂- (NR₂)]₂ (2). Compound 2 could also be formed directly from the stoichiometric mixture of THME-H₃ and [Sn(NR₂)₂]₂. Further studies revealed that 1 would also rearrange in the presence of Sn(OR)₂ to form [(μ-THME)Sn₂(μ-OR = OMe (3), OCH₂Me (4), OCH₂CH(Me)CH₂CH₃ (5), OCH₂CMe₃ (6, ONep), OC₆H₅ (7, not structurally characterized), OC₆H₄Me-3 (8), OC₆H₄Me-2 (9), OC₆H₃(Me)₂-2,6 (10), OC₆H₃(CHMe₂)₂-2,6 (11). Additionally, 3-11 could by synthesized from the reaction of 2 and the appropriate H-OR. ¹¹⁹Sn solution NMR studies of 2-11, in THF-d₈, indicate that an equilibrium between the parent complex and its disassociation products (1 and the free parent Sn alkoxy or amide precursor) exists at room temperature. This is a likely reason behind the ease of interconversion observed for 1. The generality of this exchange was further verified through the reaction of 1 with [Ti(μ-ONep)(ONep)₃]₂, which led to the isolation of (μ- ONep)₂Sn₃-THME)₂Ti(ONep)₂ (12). For 12, the solid-state structure was maintained in solution with no indication of an equilibrium.