Chemistry of a Novel Family of Tridentate Alkoxy Tin(II) Clusters

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)]2 [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(μ-THME)2Ti(ONep)2 (12). For 12, the solid-state structure was maintained in solution with no indication of an equilibrium.